Animals and human health [full issue]

ANIMALS AND HUMAN HEALTH W it-·I· ~ RLD ~ I ~ ~ ~ I , , 'l!;: THE MAGAZINE OF THE WORLD HEALTH ORGANIZATION In this issue New Director·Generol takes over at WHO 3 Zaonoses - diseases passed from animals to humans David L. Heymann Animals that infect humans Fronrois·Xovier Meslin & Kious Stohr Rift Valley fever Roy Arthur & Mike Ryon New variant Creutzfeldt· Jakob disease Mortin Zeidler & Doniel Hohn Canine rabies in Thailand Henry Wilde & Chonorong Mitmoonpitok Use of antimicrobials in food animals Kious Stohr & Fronrois·Xovier Meslin Brucellosis: a widespread public health problem Ottorino Cosivi & Aristorhos Seimenis Brucellosis in the Americas Primo Arambulo Influenza - preparing for a 21 st century pandemic Improving the health of nomadic people - the example of cystic hydatid disease (alum N. L. Macpherson When does a pet become a health hazard? Marcelo de Menezes Brondoo & Morilio Anselmo Viano do Silva Berzins Zoonoses and the immune system Ashley Robinson Diseases transmitted by pets Bruno B. Chomel Dogs and Aboriginal health in Australia Bart Currie Keeping foods of animal origin safe Fritz K. Ktiferstein & Fronrois·Xovier Meslin Animal·to·man transplants Clora J. Witt & Fronrois·Xovier Meslin WHO Publications 4 8 10 12 14 16 17 18 20 22 24 26 28 30 31 World Health • Slst Year, No. 4 July-August 1998 IX ISSN 0043-8502 Correspondence should be addressed to the Editor, World Heal th Magazine, World Health Organization, CH·l 21 l Geneva 27, Switzerland, or directly to authors, whose addresses ore given at the end of each article. HEALTH Cover: WCC/ P. Williams © World Health is the official illuslTated magazine of the World Heolth Organization. It appears six times a year in English, French and Spanish, and four times a year in Arabic and Farsi. The Arabic edition is available from WHO's Regional Office far the Eastern Mediterranean, P.O. Bax l 517, Alexandria 21 5 l l, Egypt The Far~ edition is obtainable from the Public Health Committee, Iran University Press, 85 Park Avenue, Teheran l 5875·47 48, Islamic Republic of Iran. page 6 © World Health Organization 1998 All rights reserved. Articles and photographs that are not subject ta separate copyrig ht may be reproduced far na1Karnmercial purposes, provided that WHO's copyright is duly acknowledged. Signed articles do not necessarily reflect WHO 's views. The designations employed and the presentation of material published in World Health do not imply the expression of any opinion whatsoever an the part of the Organization concerning the legal status of any countTy, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. World Health • SlstYeor, No. 4, July-August 1998 3 New Director-General takes over at WHO Dr Gro Hor/em Brundtland, the newly elected fifth Oirector-Generol of WHO. Photo WHO/ H Anenden Dr Gro Harlem Brundtland's nomination to the post of Director-General of the World Health Organization (WHO) was confirmed by the Member States during the Slst World Health Assembly which met in Geneva in May, and she began her five-year term of office on 21 July. A medical doctor and Master of Public Health, Dr Brundtland held public office in Norway for 20 years, including ten years as Prime Mini ster. In 1983, the then Secretary-General of the United Nations invited her to establish and chair the World Commission on Environment and Development; that Commission 's findings were pub- lished in 1987 in the form of a book entitled Our common future. Its recommendations subsequently led to the Earth Summit - the UN For the first time, WHO is headed by a woman. Aged 5 9, married, a mother of four and grandmother of seven, Dr Gro Harlem Brundtlond took office as Director-General of the Organization on 21 July 1998. Conference on Environment and Development (UNCED) - held in Rio de Janeiro in 1992. In her speech of acceptance after taking the oath of office at the World Health Assembly on 13 May 1998, Dr Brundtland referred to the com- plex processes of transition with which WHO must cope, and com- mented: "The transition from one century to another sees changes which will be faster and more dra- matic from an economic, social and health perspective." She warned the delegates: "WHO can and must change. It must become more effec- tive, more accountable, more trans- parent and more receptive to a changing world." The burden of disease is the burden of unfulfilled human devel- opment, she went on, and announced among the first projects to be tackled by WHO a drive to "Roll Back Malaria" by developing a new health-sector-wide approach to combat the disease at global, regional and country levels. Her second emphasis will be "to address a major cause of premature death which is dramatically increasing, killing four million people this year and - if we let it go on without action - ten million people in the year 2030 .... I refer to tobacco. I am a doctor. I believe in science and evidence. Let me state here today: tobacco is a killer." The new Director-General plans to increase the number of women employed by WHO. Among her other declared intentions for WHO are: to help to monitor, roll back and where possible eradicate communi- cable diseases; to fight to reduce the burden of noncommunicable dis- eases; to help countries to build sustainable health systems; and to speak out for health and back the case for health actions with solid evidence. The outgoing Director-General , Dr Hiroshi Nakajima, appointed in 1988 and who served two terms of office, offered his good wishes to Dr Brundtland during the Assembly, and said: "Her gifts, her experience and her convictions will be of im- mense value to her and to WHO in the fulfilment of her task. I know that the Organization will be in good hands." On her first day in office, Dr Brundtland addressed WHO staff, representatives of the UN missions in Geneva and the media. She outlined WHO's future policy and presented the new senior management team, including nine executive directors from around the world - five women and four men, most of whom have been called upon to serve WHO for the first time. The new Director-General ex- pressed her "great expectation and excitement" and her belief in the immense potential of WHO. She said: "We can make a difference. We can build healthy communities and populations. We can combat ill-health. We can do our part to combat poverty and suffering. Nothing in life - as I see it - has more meaning." • 4 World Health • 51 st Year, No. 4, July-August 1998 Zoonoses - diseases passed from animals to humans David L. Heymann Many of the human diseases that are emerging and re-emerging at the close of the 20th century are caused by pathogens originating from an animal or from products of animal origin. A wide variety of animal species, both do- mesticated and wild, act as reservoirs for these pathogens, which may be viruses, bacteria or parasites. Quite apart from their direct impact on human health through the sickness and death that they cause, these zoonoses can have dramatic eco- nomic consequences, especially for people who depend on livestock for survival. Zoonotic diseases can rapidly cause extensive human suffering and death. For example, a recent out- break of Rift VaJley fever in Kenya caused tens of thousands of human cases and hundreds of deaths; this virus is transmitted to humans through mosquito bites and direct contact with infected animals, mainly cattle and sheep (see p.7). Other zoonotic diseases can spread invisi- bly, at least at the outset. New vari- ant Creutzfeldt-Jakob disease (nvCJD), for instance, almost cer- tainly caused by the bovine spongi- form encephalopathy (BSE) agent, has an unknown average incubation period ; estimates vary from 10 to over 20 years . nvCJD causes rapid and fatal brain degeneration when it appears, but it is not yet known how many human beings were infected before appropriate control measures were taken. It could be very few, but it could be thousands, or more (see p.8). Considering the wide span of animal species involved and the usually complex natural history of the pathogens concerned, the effec- tive surveillance, prevention and control of zoonotic diseases pose a During the recent outbreak of Rift Valley Fever in Kenya, mosquitos were trapped and then studied in order to determine which species were responsible for the transmission of the disease. Photo WHO/ R. Arthur real challenge to public health. The alteration of our environment and the establishment of human settle- ments in formerly uninhabited areas, particularly in the tropics, are two further factors that favour the emer- gence of diseases whose agents may have remained for centuries in nature. To these are added the ever- greater demand for animal protein foods, the acceleration of interna- tional trade, and the increasing number of people who are poten- tially more susceptible to oppor- tunistic infection by agents of animal origin. Further problems stem from the use of antimicrobial substances in food animals, including their use as growth-promoters. Therapeutic use of antibiotics in animals, as in humans, is necessary, but some major animal pathogens responsible for outbreaks of foodborne diseases in humans are now proving resistant to the antibiotics used in human medicine. This has to be taken into account in the overall strategy to control antimicrobial resistance. WHO's task in this increasingly important area of public health is to strengthen the capacity of countries and the international community to prevent such dangers from develop- ing, and to minimize their impact on public health. To do this, the Organization works with its partners within a global framework to reshape and strengthen the network for com- municable disease surveillance and control. The aim is to detect and contain the spread of viral, bacterial and zoonotic diseases where and when they occur. This issue of World Health looks more closely at some of the problems involved and the ways in which they can be solved. • Dr David L. Heymann is Executive Director for Communicable Diseases, World Health Organization, 121 1 Geneva 27, Switzerland. World Health • SlstYeor, No. 4, July-August 1998 5 Animals that infect humans Fran~ois-Xavier Meslin & Klaus Stohr In Gabon, a hunter is proud of the monkeys he caught in the forest . Monkeys are suspected to be the link between the natural reseNoir of the Ebola virus and man. Photo WHO/G. Rodier F or better or for worse, human beings have always interacted in a wide variety of ways with the other animal species that share this planet. We have domesticated some as work animals, reared or hunted others for food, brought others into our homes as pets and involuntarily fed and sheltered others as pests. In rich and poor countries alike, animals and their products are ever more closely involved in our everyday lives. Diseases occurring in a great range of animal species can cross the species barrier and give rise to emerging and re-emerging diseases in humans. The pathogens that cause these diseases may reach us through our physical contact with living animals and their waste products or through our consumption of certain food products of animal origin. Below are some examples of health problems that have arisen recently as a result of the complex interrelation- ships between animals and humans. Equine encephalitis An epidemic outbreak of Venezuelan equine encephalitis (VEE) was reported in the border area between Colombia and Venezuela, starting in early September 1995. By the end of that month, 8825 human cases of VEE had been reported, and four deaths had occurred in Venezuela. In Colombia, more than 450 cases were reported. This is the most severe of several viral diseases in horses, and the virus can be transmit- ted to humans by mosquito bites. Most infections are relatively mild, but symptoms include severe headache, chills, fever, muscular pain, nausea and vomiting; fewer than 1 % of cases are fatal. Outbreaks can be prevented by the regular immunization of horses carried out within the framework of public health programmes. Monkeypox Monkeypox is a viral disease occur- ring in monkeys and squirrels in the rain forests of central and western Africa. It is transmissible to humans and causes a syndrome similar to smallpox. In 1996 and 1997, more than 500 suspect cases of human monkeypox were reported in the Kasai Oriental province of the Democratic Republic of the Congo. Many of the cases were in children under 16 years old. No deaths were reported, and by the end of 1997 transmission appeared to have ceased at the site of the outbreak and in the surrounding villages. The two inves- tigations conducted on site by WHO indicated that person-to-person transmission accounted for most of the cases that occurred at that time, in contrast to sporadic earlier cases, which had been caused by animal-to- human transmission. Further analy- sis will help to elucidate the risk factors for transmission. Ebola and Ebola-related viruses In 1976, the Ebola virus attracted worldwide attention with the out- breaks in Zaire (318 cases) and Sudan (284 cases), both showing very high case mortality rates (53% in Sudan and 88% in Zaire). The first patients may have been in con- tact with infected animals or their products (bats or rodents in Sudan, meat from monkeys or wild antelopes in Zaire), but investiga- tions into the possible animal reser- voir remained inconclusive. Further sporadic cases were reported in the following years , and in January 1995 a new Ebola epidemic was reported in Kikwit, Zaire, with a total of 315 cases and 244 deaths. The following year two outbreaks occurred in Gabon, causing about 40 deaths; most of the patients there had been in contact with a dead chimpanzee which had been butchered for food. However, nothing definite is known about the reservoir of Ebola virus, although certain species of monkey and apes seem to be the only animal victims of the disease in the wild. Consequently, WHO has initiated a multidisciplinary study in the Tai forest in Cote d'Ivoire to track down the natural reservoir of the virus; this is essential to understand the mecha- nisms of its transmission in nature and help to prevent future outbreaks. Many hundreds of specimens have been collected, ranging from insects to shrews, bats and apes. The results of the study are expected to be pub- lished shortly. Bovine spongiform encephalopathy (BSE) BSE is a fatal neurological disease of cattle which first came to the atten- tion of the scientific community in November 1986 with its appearance in cattle in the United Kingdom. 6 This homeless Indian woman lives in o cow shed. When humans live in close proximity to cattle, they may contract such zoonoses as bovine tuberculosis. Zoonoses prevention and control remains a maior area of concern in developing countries. Photo WCC/G. Thiel© Since 1986, some 170 OOO cases of this disease have been confirmed in the UK. Epidemiological studies suggested that the source lay in cattle-feed prepared from carcasses of ruminants infected with a trans- missible spongiform encephalopathy agent. Modifications in the process used for preparing cattle-feed intro- duced in 1981 and 1982 may have been a risk factor by allowing the pathogen to survive in the feed. By June 1996, BSE had been reported in 13 countries and areas outside the United Kingdom. In one group of countries - Belgium, France, Ireland, Luxembourg, the Netherlands, Portugal and Switzerland - the disease occurred in native cattle, and could be linked to the importation of potentially infected cattle-feed from the UK. In another group - Canada, Denmark, the Falk.land Islands, Germany, Italy and Oman - cases were identified only in cattle imported from the UK. The disease is now on the decline in that country. Although the implications for public health had been evaluated, and measures proposed for reducing risks, the problems acquired a new dimension in March 1996, when the UK health authorities announced the appearance of a cluster of 10 humans suffering from what appeared to be a new variant of Creutzfeldt-Jakob disease (nvCJD). CJD is a rare degenerative brain disease with a worldwide distribution. Like BSE, it belongs to the group of transmissible spongiform encephalopathy. At present the number of people af- fected with nvCJD stands at 27 in the UK and one in France. Recent evidence from various studies further supports the hypothe- sis of a link between nvCJD and BSE made in March 96 on circum- stantial evidence. Because of its long incubation period, the possibil- ity of a significant epidemic of nvCJD occurring with in the next 10 to 15 years cannot yet be dismissed. As exposure to the BSE agent may extend to populations outside the UK and Western Europe, WHO is strengthening global surveillance of CJD and its variants to ascertain the number and distribution of any future cases. Outlook for the future The rising incidence of zoonotic diseases is likely to continue in view of foreseeable global changes over the next few decades such as popula- tion growth, urbanization and cli- mate change. Although the prevalence of brucellosis, tuberculosis, canine rabies and other major zoonoses has been greatly reduced in industrial- ized countries, zoonoses prevention and control will remain an area of major concern in most developing ones. Recent observations suggest that expenses related to the preven- World Health • SlstYeor, No. 4, July-August 1998 tion of zoonotic diseases in people are likely to increase dramatically in these countries in the near future if no programmes for their control in animal reservoirs are implemented. Diseases such as brucellosis, rabies and bovine tuberculosis cancer- tainly be brought under control in most parts of the world during the first decade of the third millennium but this will require constant efforts for the next 20 to 30 years. As zoonoses and animal diseases with potential implications for human health wi ll continue to emerge and re-emerge, surveillance of these diseases will need to be reinforced and maintained at country level and internationally. In view of unplanned urbanization and the associated shortage of basic facili- ties, large cities everywhere will need a strategy for responding to human and animal health problems. At the same time, comprehensive plans will be needed to reduce rural- urban migration. These plans should include the improvement of rural employment and food availability by the promotion of animal production projects, and the improvement of health through zoonoses control and reduction of environmental pollution related to animal rearing. In view of the usually complex transmission cycles of these dis- eases, further collaboration is essen- tial between all the professions and institutions involved. This is partic- ularly true in the field of foodborne disease prevention and control, where all professional groups in- volved in the food chain, from the farms where the animals are raised for food to the consumer's plate, should collaborate closely in meet- ing the world's need for wholesome and safe animal food products. • Dr Fronc;:ois·Xavier Mes/in is Chief of the Zoonotic Diseases Unit and Dr Klaus Stohr is a scientist with the same programme, Division of Emerging and Other Communicable Diseases Surveillance and Control, World Health Organization, 121 1 Geneva 27, Switzerland. World Health • Sl stYear, No. 4, July-August 1998 7 Rift Valley fever Ray Arthur & Mike Ryan A disease which attacked both humans and animals late last year in parts of Kenya and Somalia triggered a major international investigation and proved to be the viral disease known as Rift Valley fever. An international medical team arriving in the Kenyan part of the Rift Valley, which had been cut off by maior flooding. By early February this year, the latest outbreak of Rift Valley Fever had claimed 400 lives in Kenya, and 80 in Somalia. Photo WHO/M Ryan In December 1997, the Kenyan Ministry of Health and WHO in Nairobi received reports of scores of unexplained deaths in the North- Eastern province of Kenya and in southern Somalia. The symptoms of those affected included an acute fever and headache followed by haemorrhaging, with bloody stools, vomiting of blood and bleeding from other mucosa] sites. At the same time local health officials reported high rates of spontaneous abortion and deaths from haemorrhage among domestic animals. Diagnostic testing of 36 human blood samples at the National Institute of Virology in South Africa and at the Centers for Disease Control and Prevention (CDC) in Atlanta, USA, confirmed acute infection with Rift Valley fever (RVF) virus in 42% of the cases. The outbreak followed torrential rains which began in late October 1997 and continued into January, causing the worst flooding in the region since 1961. Although the floods compli- cated efforts to track down cases, active surveillance in Kenya's North- Eastern province, conducted by WHO, the Kenyan Ministry of Health and international relief orga- nizations, had by the year-end identi- fied 170 deaths from a "bleeding disease". The killer disease waned in early February 1998, but not before it had claimed some 250 lives. Over 3000 mosquitos were col- lected in the affected zone and were found to belong to nine different species, three of which had been previously implicated in the trans- mission of RVF. Analysis of blood samples from humans and livestock in the North-Eastern Province of Kenya led to the conclusion that contact with livestock, including herding, milking, slaughtering and sheltering animals in the home, was associated with acute RVF infection. Livestock owners reported losses of about 70% of their animals. Other infections contributing to the high mortality in animals ranged from pneumonia to skin diseases. The scale of the outbreak and the eco- nomic losses it caused have yet to be fully assessed. The Rift Valley fever virus was first isolated in Kenya in 1931, when it was recognized as causing high death and abortion rates in ewes and newborn lambs. The most severe epidemic was in Egypt where the virus was recognized for the first time during 1977-1978 and was associated with at least 18 OOO human infections and 598 deaths, accompanied by almost universal abortion in pregnant ewes and deaths among lambs. Outbreaks in Kenya occur periodically following heavy rains which flood natural depressions and encourage the hatching of virus- i nfected Aedes mosquito eggs, the reservoir of the virus. Domestic animals are the amplifying hosts which infect the other mosquito species that spread the virus among the animals and to humans. Transmission to humans can also occur by contact with blood or body fluids from infected animals. Efforts are now under way to test the feasibility of using remote-sens- ing satellite data to give advance warning of climatic conditions that favour the emergence of RVF and thereby help target areas for animal vaccination. These and other animal and human surveillance activities will make earlier identification of the disease possible and help the health authorities to take preventive action. • Dr Ray Arthur and Dr Mike Ryan are with the Division of Emerging and Other Communicable Diseases Surveillance and Control, World Health Organization, 1211 Geneva 27, Switzerland. 8 World Health • SlstYeor, No. 4, July-August 1998 New-variant Creutzfeldt·Jakob disease Martin Zeidler & Daniel Hahn Agroup of diseases afffecting the central nervous system occur in several animal species, including humans. These conditions are called transmissible spongiform encephalopathies (TSE). They can be passed from animal to animal in the laboratory and are characterized by spongy degenera- tion of the brain. The one that oc- curs most commonly in humans is called Creutzfeldt-Jakob disease (CJD). Until recently, TSEs in humans were thought to exist inde- pendently of those in other animals, but now the agent which causes them appears to have crossed the species barrier. At present there is no reliable pre-symptomatic test for TSE and no effective treatment has yet been found that can stop the underlying disease process. A TSE affecting cattle - bovine spongiform encephalopathy (BSE) - was first reported in the United Kingdom in 1986, and since then about 170 OOO cases have occurred in that country alone. Small num- bers of BSE cases have also been reported in native cattle in Belgium, France, Ireland, Luxembourg, the Netherlands, Portugal and Switzerland. Cases have also been found in Canada, Denmark, the Falkland Islands (Malvinas), Germany, Italy, and Oman in ani- mals imported from the United Kingdom. Food ban It is thought that BSE was caused by animals being given feed supple- ments made from the remains of sheep contaminated with scrapie - a TSE that affects sheep. A reduction in the use of solvents and heat in the manufacturing process in the United Kingdom around 1980, combined Seen under the microscope, a specimen from the bro in of a victim of the new variant of Creutzfeldt· Jakob disease demonstrates a consistent and previously unseen pattern of multiple florid plaques, which con be distinguished on the left of the photo. Photo WHO, by courtesy of Dr). Ironside with other factors, may have been the cause of the transmissible agent remaining active. In 1989 brain, spinal cord and certain other organs from cattle - the specified bovine offals (SBO) considered to pose a potential risk to humans - were banned from foodstuffs in the United Kingdom. Other European Union countries that had identified cases of BSE later established thier own SBO list also banned their use in food. Opinions differ as to the nature of the TSE agent. According to one theory (the prion theory) it is com- posed largely, if not entirely, of a self-replicating protein. A second theory is that the agent is similar to a virus and possesses nucleic acids which carry genetic information. Evidence gathered over the past 10 years supports the prion theory, but the TSE agent is able to form multi- ple strains, and this is more like the behaviour of a virus. Four different forms of CJD have been identified: sporadic, familial, iatrogenic, and new variant. • Sporadic CJD, which accounts for about 85% of cases, usually affects individuals between the ages of 50 and 75 , and is charac- terized by a rapidly progressive dementia, jerking movements of the limbs, and a specific abnor- mal brain wave pattern. The cause of sporadic CJD remains unknown and there is no evi- dence of a causal link with any animal TSE. • Familial CJD accounts for 10-15% of cases and is an inher- ited disease associated with a gene mutation. • Iatrogenic CJD, accounting for less than 5% of cases, results from the accidental transmission of the causative agent from contaminated materials - such as neurosurgical instruments - during medical or surgical treat- ment. • New variant CJD (nvCJD) is a new disease which was first reported in March 1996 and which is probably linked with exposure to the BSE agent. Unlike most cases of CJD this variant form has affected young people. The average age of patients with nvCJD is 27 years compared with 65 years for other World Health • SlstYear, No. 4, July-August 1998 forms of CJD; and the illness generally lasts longer - 14 months on average compared with 4-5 months. When viewed under a microscope, the brain of patients with the new variant demonstrates a consistent but previously unseen pattern. Clinical features Patients with nvCJD usually experi- ence psychiatric symptoms early in the illness which most commonly take the form of depression, or less often a schizophrenia-like psychosis. Persistent and unpleasant sensory symptoms, such as tingling or burn- ing feelings , have been experienced by half of the cases early in the illness. Neurological signs, includ- ing unsteadiness and involuntary jerking or fidgeting, develop as the illness progresses, and just before death patients are unable to move or to talk. It is important to note that depression and sensory symptoms are common in the general popula- tion and are usually not due to any serious underlying disease. The first patient with nvCJD became ill in January 1994. By the end of June 1998, 28 cases had been identified - 27 in the United Kingdom and one in France. There was no concentration of cases in any particular area of the United Kingdom. Moreover, the occupa- tions, diets and medical histories of the cases do not provide convincing evidence that, as a group, they might have had a greater exposure to the BSE agent than the rest of the popu- lation . Information on the potential risk factors has been published for 10 cases; nine cases were reported to have eaten beef or beef products since 1986, but none was reported to have eaten brain. One of the cases had been a strict vegetarian since 1991. Diagnosing new variant CJD Patients with the new variant CJD do not have the characteristic brain wave pattern of sporadic CJD. Blood and spinal fluid tests are normal or Processing beef in the United Kingdom. The ports which are considered to pose a potential risk to human health are discarded and destroyed Photo WHO, by courtesy of Or B. Hornlimann unhelpful. Four cases were reported to have a specific abnormality re- vealed by magnetic resonance brain scanning and this may in future be a useful diagnostic sign. At present, the diagnosis of nvCJD can only be confirmed following examination of the brain under the microscope. Characteristically, multiple minute protein aggregates surrounded by holes are seen, with a daisy-like appearance, described as "florid plaques" (see photograph, p.8) . All 23 cases tested to date were in people with a particular genetic characteris- tic found in only 40% of the general population. It is possible, however, that nvCJD may occur in people with other genetic features in the future. New evidence Cases of nvCJD and BSE started to increase in the same countries at around the same time which led to the hypothesis that they were linked. Scientific evidence further support- ing a link includes the identification of microscopic features similar to nvCJD in the brains of monkeys inoculated with BSE, and the demon- stration that nvCJD is associated with a molecular marker that distin- guishes it from other forms of CJD and which resembles that seen in BSE transmitted to a number of other species. The most recent and powerful evidence comes from studies show- ing that the transmission characteris- tics of BSE and nvCJD in mice are almost identical, strongly suggesting that they are due to the same causative agent. In addition, trans- genic mice carrying an important human gene have been shown to be susceptible to BSE, and no other convincing hypothesis for the occur- rence of nvCJD has been proposed. Intensive CJD surveillance in five European countries with low poten- tial exposure to the BSE agent has failed to identify any cases. In con- clusion, the most likely cause of nvCJD is exposure to the BSE agent, probably in food contaminated by affected cattle brain or spinal cord. We do not have sufficient informa- tion at present to make any well- founded prediction about the future number of nvCJD cases. WHO global surveillance 9 Since 1991 WHO has convened seven scientific consultations on issues related to animal and human TSEs. The potential future public health implications of nvCJD were examined by a WHO consultation in May 1996 and reviewed in February 1998. As exposure to the BSE agent may extend to populations outside the United Kingdom and western Europe, strengthened global surveil- lance of CJD and its variants was recommended in 1996 in order to determine the number and distribu- tion of any future cases. Surveillance has already been established in many European countries, Australia, Canada and the United States of America, and WHO is initiating surveillance in other, mainly devel- oping, countries. It is anticipated that these activities will provide information that is important for enhancing the protection and plan- ning of public health worldwide. • Or Martin Zeidler is with the Department of Clinical Neurology, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, Scotland Or Daniel Hahn's address is 30A Clapham Road, London SW9 OJQ, England 10 World Health • SlstYeor, No. 4, July-August 1998 Canine rabies in Thailand Henry Wilde & Chanarong Mitmoonpitak The effects of the rabies virus have been known since Babylonian times. The ancient Romans referred to the presence of a 'transmissible poison ' in the saliva of mad dogs. The virus is usually introduced into humans through the bites of infected animals but other means of transmission are possible. Infected licks on mucous membranes and the inhalation of infected bat secre- tions have resulted in deaths in humans, and cases are recorded of people being infected with rabies after receiving corneal grafts from donors in whom the disease had been undiagnosed. There is no documented case of human-to-human transmission from close personal contact. Reservoirs of rabies virus exist among dogs, cats and many wi ld mammals, in- cluding foxes , skunks, raccoons, jackals, wolves, and bats. In much of Asia, Africa, and South America, however, it is the dog that presents the greatest risk to humans. After entering a mammalian body the rabies virus 'rests' or multiplies slowly at the inoculation site. It then invades the nearest nerve tissue and slowly, over weeks or months, ascends into the spinal cord and brain . There it multiplies , causing rapid death. The unde- tectable incubation period ranges from a few days to many years after primary infection. In Thailand most infected humans fall ill and die within 14 to 60 days after their exposure. Although it is generally considered an invariably fatal dis- ease a few isolated survivors have been documented. All have suffered brain damage, however. The World Health Organization estimates the annual number of human deaths from rabies at over 50 OOO, but we believe the figure could be higher because of the many The French scientist Louis Posteur ( 1822-1895) developed the first voccine ogoinst robies. Todoy, sofe, potent ond offordoble new vaccines ore available in many countries. Photo WHO The World Health Organization estimates the annual number of human deaths from rabies at over 50 OOO, but the figure could be higher because of the many deaths that go unreported. However, newer effective, safe and less- expensive second-generation tissue or avian culture rabies vaccines are now available in most parts of the world. deaths that go unreported in remote parts of the world. Reported deaths from rabies outnumber those due to polio, Japanese encephalitis, meningococcal meningitis, schisto- somiasis, cholera and Creutzfeldt- Jakob disease. Rabies in cattle and other domestic mammals also causes economic damage. A dog 's saliva becomes infective up to one week prior to the dog becoming ill and it remains infective up to the time of death, which is rarely longer than 10 days after onset of symp- toms. Unlike humans, some dogs may survive rabies infection. Rabies in humans is preventable by early wound cleansing and vacci- nation with modern vaccines. Since it takes at least 10 days for a previously unvaccinated human to develop antibodies to rabies from vaccina- tion, anti-rabies immunoglobulin must also be administered on the first day of treatment to bridge the ' un- protected period' . It must be injected into the bite sites to neutralize the virus. This immunoglobulin can be made from immunized humans or horses. Post-exposure treatment with vaccine and immunoglobulin pro- vides virtually 100% protection if administered immediately and ac- cording to WHO recommendations. The problem is, however, that rabies immunoglobulins and modern vac- cines are expensive and not always readi ly available in all parts of the world. This is why vaccines derived from crude nerve tissue, locally produced from sheep or mouse brains, are still used in nearly 90% of treatments worldwide. Only expert post-exposure treat- ment using modern cell-culture vaccine can reduce the human death toll, as has been demonstrated in Thailand. The dramatic reduction achieved there was brought about by abolishi ng the use of nerve-tissue- World Health • Sl stYear, No. 4, July-August 1998 This rabid dog hos on irrepressible urge to bite. Dogs present the greatest risks lo man. Photo Thai Red Cross Society © derived vaccines in 1986. The older vaccines were feared by the public; many people preferred to consult a faith healer or a dog bite 'specialist' rather than receive the 17 painful and dangerous injections of vaccine produced from the brains of lambs or newborn mice. Abolition of these vaccines was made possible by the introduction of low-cost second- generation tissue culture vaccines and an intensive public education campaign. Unfortunately, modern post-exposure treatment for all will not solve the real problem of rabies because it does not remove the ani- mal reservoir. Moreover, it is expen- sive. The minimum cost of a single dose of human diploid cell rabies vaccine (first-generation tissue culture) is approximately US$ 30. An average course of treatment for an adult, which requires five spaced doses plus rabies immunoglobulin (of equine origin), costs approxi- mately $200, which in most develop- ing countries represents more than a month's wages. However, newer effective, safe and less-expensive second-generation tissue or avian culture rabies vaccines are now available in most parts of the world. None the less, being bitten by a possibly rabid animal results in much anxiety and suffering and represents a severe economic bur- den. In Thailand, as in other parts of Asia, Africa, and South America, it is mostly stray or village dogs that carry the disease. Mass vaccination campaigns are organized annually. Most stray dogs, however, have a short life expectancy resulting in rapid population turnover. They are not easily caught and vaccinated. It is estimated that in Bangkok alone there are at least 100 OOO stray dogs with an average age of one and a half years and that there is approximately one dog for every six humans. Fifteen per cent of the dogs we examined and found rabid were under the age of three months and only 10% had been vaccinated. In spite of annual campaigns by munic- ipal authorities, approximately 80% of stray dogs caught at random in Bangkok have never been vacci- nated against rabies. A single injection of rabies vaccine does not confer long-term immunity against infection and it is rarely possible to inoculate stray dogs more than once. One solution would be to use an oral dog vaccine like the one being used successfully for foxes in Europe. Another would be to control the stray and commu- nity dog population by sterilization and destruction, but this is difficult to do in a poor tropical country owing to logistical problems and cultural and religious constraints. 11 A neighbouring country showed in the 1950s that vigorous dog control and mandatory vaccination can virtually eliminate canine rabies. • Dr Henry Wilde, Professor of Medicine, is with the Oueen Saovabha Memorial Institute, Thai Red Cross Society, and Dr Chanarong Mitmoonpitak, Doctor of Veterinary Medicine, is with the Rabies Diagnostic Unit at the same institute. Their address is 187 l Rama IV Road, Bangkok l 0330, Thailand. In a Nepalese village, people are encouraged to bring their dogs to be vaccinated against rabies os part of a community prevention campaign. Photo WHO/ A. Kappeler 12 World Health • Sl stYeor, No. 4, July-August 1998 Use of antimicrobials in food animals Klaus Stohr & Fran~ois-Xavier Meslin Industrial poult,y production in Europe. Antibiotics are used to promote growth in food animals. This practice may threaten the efficiency of some of the drugs used to fight infection in both animals and man . Photo WHO/K Stohr The use of veterinary antimicrobial substances to keep farm animals disease-free and increase production may encourage the transmission of drug-resistant germs to humans. Antimicrobial drugs are widely used for treating infections in both humans and animals. Unfortunately, however, their use inevitably leads to the development of germs that are resistant to those drugs. Depending on the mecha- nisms involved and factors such as dosage, length of treatment, and how the drugs are administered, the development of resistance will be greater for certain combinations of organisms and antimicrobials than for others. Some such drugs have been in use for more than five decades, giving antimicrobial resis- tance ample time to develop and become a significant problem for the treatment of certain infections. Today it is clear that most resis- tance problems in humans stem from the use and misuse of antimicrobials in human medicine. They are all too often prescribed for conditions in which they are known not to be effective (for instance, viral infec- tions). Even when they are pre- scribed properly, patients may not comply with instructions on how often to take them, and for how long. In some countries, antimicrobial substances are used extensively in animal and plant agriculture. Most of them are used at very low doses in livestock for growth promotion. Several of the organisms that infect humans originate from animals and are transmitted through food, water or direct contact. Some of these organisms, including Salmonella, Campylobacter, Escherichia and Enterococcus, are increasingly showing resistance, and part of this increase has been linked to the treatment of food animals with antimicrobials. Although the public health impact of resistance due to antimicrobial use in food animals is certainly small compared with that of resistance originating in humans, the situation needs to be carefully monitored. The development of resistance to certain "last-resort" anti- microbials - those that are kept in reserve for use when other drugs have failed - could have serious consequences for both humans and animals. Questions about the use of anti- microbials in food animals have been raised and debated ever since the 1950s, when the feeding of low levels of these drugs to promote growth in food animals began. Over the years, various scientific bodies have studied the public health im- pact of such use but definitive an- swers have not been forthcoming. Perhaps the best known study was that of the United Kingdom's Swann Committee of 1969, which recom- mended that for growth promotion use should be made only of anti- biotics that have "little or no appli- cation as therapeutic agents in man or animals and will not impair the efficacy of a prescribed therapeutic drug through the development of resistant strains of organisms" . Data on the extent and trends of resistance are scarce, and those that World Health • SlstYear, No. 4, July-August 1998 Resistance to antibiotics often stems from misuse in human medicine. These drugs should be limited only lo complaints for which they are effective, and the prescription should be scrupulously followed Photo WHO/PAHO/ A Waak are available consist mostly of labo- ratory test results that do not always correlate with data on use of growth promoters and the treatment of ani- mals in practice. Some regulatory actions have nevertheless been taken. For instance, following the emer- gence of resistant enterococci (bac- teria) in animals , the European Commission decided to ban the use of avoparcin as a growth promoter in poultry. WHO's role Given the prevailing uncertainty about the implications of antimicro- bial resistance in animals for public health, WHO's Division of Emerging and other Communicable Diseases Surveillance and Control (EMC) has opened the debate on these issues so as to determine what should be done at national and international level. WHO organized a meeting of experts on the medical impact of antimicro- bial use in food animals in October 1997. Priority problems were reflected in the examples the participants gave of the medical consequences of resistance of animal origin. Specific organisms identified included Salmonella, Campylobacter, Enterococcus and Escherichia coli, and the drugs concerned included fluoroquinolones and avoparcin. Evidence was presented which suggested that the use of antimicro- bials in animals encourages the emergence of antimicrobial-resistant Salmonella serotypes. Such bacteria are known to be mainly transmitted to humans in food or through direct contact with animals. A recent example is S. typhimurium DT104, which is resistant to at least five antimicrobials. Since fluoroquinolones were introduced for treatment of disease in food-producing animals, Salmonella serotypes with reduced susceptibility to fluoroquinolones have been observed in animals and isolated from food in France, Germany, Ireland, the Netherlands, Spain, and the United Kingdom. After fluoroquinolones were used in poultry, there was a significant rise in the prevalence of fluoro-quinolone-resistant Campylobacter jejuni isolated from live poultry, poultry meat and hu- mans. Before this use in poultry, no resistant strains had been reported in humans who had not had previous exposure to quinolones. However, fluoroquinolone-resistant C. jejuni have only been associated very rarely with treatment failures in humans. Multiresistant strains of Escherichia coli have also appeared following the use of broad-spectrum antimicrobials in both livestock and humans. The development of anti- microbial resistance in E. coli gives special cause for alarm, not least because identical resistance genes have been found in E. coli both in animals and in humans. Need for safeguards 13 A WHO consultation held in October 1997 recommended that the use of any antimicrobial agent for growth promotion in animals should be terminated if the same agent is used in human therapeutics or is known to favour the development of cross-resistance to antimicrobial drugs used in human medicine. National authorities were urged to define threshold levels of resistance in bacteria and ensure that no anti- microbial is administered to a food animal unless that substance has been evaluated and authorized by national authorities. It was also recommended that countries should monitor the prevalence of resistant bacteria in food-producing animal populations and animal-based food products, and that WHO should take the lead in coordinating international efforts in monitoring resistance of bacteria isolated from food of animal origin and food animals. WHO is now planning to set up a network of laboratories which will regularly test samples from food animals and foods of animal origin and report the results to WHO. The laboratories involved will seek to establish national networks ex- pressly to monitor antimicrobial resistance. WHO will work with other international organizations such as the Food and Agriculture Organization of the United Nations (FAO) and the Office International des Epizooties (OIE) to assess risks of antimicrobial resistance which may arise in the context of each country's situation and needs. • Dr Klaus Stohr is a scientist in the Zoonotic Diseases Unit and Dr Fram;:ois-Xavier Mes/in is chief of the unit, Division of Emerging and other Communicable Diseases Surveillance and Control, World Health Organization, 12 l l Geneva 27, Switzerland 14 World Health • Sl stYeor, No. 4, July-August 1998 Brucellosis: a widespread public health problem Ottorino Cosivi & Aristarhos Seimenis Brucellosis can be prevented in humans by limiting or, ideally, eliminating the disease in the animal population and by avoiding contact with infected animals and consumption of raw milk and milk products Of all the zoonoses that have both public health and eco-nomic implications, brucel- losis (also known as Mediten-anean fever, remittent fever, Malta fever and undulant fever) is the most widespread. The first clinical de- scription of it dates back to 1860, and the cause of the disease was discov- ered in 1887, when a British an-ny doctor, David Bruce, identified the microbe, which was named after him. Later, in 1905, infected goats and their milk were identified as a source of infection in humans. The risk to humans The incubation period for brucellosis is usually one to three weeks, but sometimes it may be several months. Symptoms of the illness vary from mild and self-limiting to severe, though they are seldom life-threaten- ing. Onset can be sudden or insidi- ous, and can be accompanied by persistent or intermittent fever. The general symptoms resemble those of many other febrile diseases, but brucellosis also affects the bones and A West African "Peul" woman milking a goat in northern Senegal Health education con discour- age people from drinking untreated milk which may carry the Bruce/fa microbe. Photo WHO/FA0/1 Balderi muscles, producing generalized aches and pains, and is associated with exhaustion and depression. The duration of the disease can vary from a few weeks to several months. Laboratory tests are needed to con- firm the clinical diagnosis. Brucellosis is transmitted through contaminated untreated milk and milk products, and through direct contact with infected cattle, sheep, goats, pigs, camels, buffaloes, wild ruminants and, most recently, seals. Animal carcasses and aborted fetuses are also sources of the disease. Millions of individuals are at risk worldwide, especially in countries where infection in animals has not been brought under control, proce- dures for heat treatment of milk (such as pasteurization) are not routinely applied, and standards of hygiene in animal husbandry are low. In countries around the Mediten-anean, efforts are being made to control the disease in ani- mals, but brucellosis persists in sheep and goats, causing widespread infection in humans. In these coun- tries the annual incidence of brucel- losis in people varies from less than 1 to 78 cases per 100 OOO popula- tion. In confined endemic areas where no animal control measures are applied more than 550 cases per 100 OOO population have been re- ported. Reported cases do not tell the full story, however. Although human brucellosis is a notifiable disease in many countries, the true incidence is thought to be between 10 and 25 times as high as the reported figures . Very often the disease remains unrecognized as a result of inaccu- rate diagnosis, and is thus reported as a different disease, or as "fever of unknown origin". A recent human survey conducted in Saudi Arabia fou nd that almost 20% of the popu- lation had had the infection and the disease was still active in over 2% of those examined. Similar figures can be expected from most countries in World Health • SlstYear, No. 4, July-August 1998 15 Collecting fresh milk in Pakistan. Heat treatment ensures that milk and milk products ore safe. Photo WHO/ FAO/ G. Bizzorri A veterinarian in Afghanistan examines a goat as port of on effort to ensure that the livestock remain healthy. which the disease in endemic in the animal population, and a higher prevalence should be expected in occupationally exposed groups such as veterinarians, farmers and slaughter-house workers. Strategies for brucellosis control The disease can be prevented in humans by limiting or, ideally, elimi- nating the disease in the animal population and by avoiding contact with infected animals and consump- tion of raw milk and raw milk prod- ucts. Brucellosis control pro- grammes in animals include testing for the disease, slaughtering infected animals and vaccinating animals at risk. In several countries these programmes have been successful, resulting in a major reduction of the incidence in humans. Proper heat treatment of milk or milk products is important for effective prevention of brucellosis in humans. However, social and economic constraints can impede the wider application of such measures. Health education is essen- tial for the success of any prevention and control activities, and should form an integral part of all phases of public health and animal health brucellosis pro-grammes. Antimicrobials (drugs that de- stroy or inhibit microbes) are effec- tive against brucellosis, but only if several of them are used at once over a period of several weeks. Antimicrobial-resistant strains of Photo WHO/ FAO/ M. Griffin Brucella have been reported but their clinical implications are not yet fully understood. Some of the commonly used antimicrobials for brucellosis treatment, such as rifampicin and streptomycin, are also preferred drugs for the treatment of tuberculo- sis. The current emergence of strains of tuberculosis bacteria that are resistant to a number of such drugs makes it increasingly important to find an alternative treatment for brucellosis, using antimicrobial agents not employed for tuberculosis. Animal brucellosis, also known as Bang's disease, causes serious economic losses in developing coun- tries . It provokes spontaneous abor- tions, infertility, and milk and meat production losses, and makes it necessary to place restrictions on trade in animals and animal prod- ucts . This impairs economic devel- opment, particularly in the case of smail-scale livestock owners, one of the most vulnerable groups in many rural populations. Brucellosis and WHO Brucellosis in humans and animals is increasing in many parts of the world, including the Mediterranean region, western Asia and parts of Africa, eastern Europe and Latin America. A number of WHO pro- grammes are aimed at strengthening brucellosis surveillance and control activities at national , regional and global level s. In collaboration with the Food and Agriculture Organization of the United Nations and the Office international des Epizooties, WHO is promoting a regional control programme in the eastern Mediterranean area. The Mediterranean Zoonoses Control Programme of WHO is coordinating a study to evaluate new treatment regimens for human brucellosis. WHO and the United Nations Development Programme are collab- orating with the Palestinian Authority in a programme for the control of human and animal brucel- losis in the West Bank and Gaza Strip. WHO's Regional Office for the Americas has launched an initia- tive for bovine brucellosis elimina- tion in Latin American countries. The Organization also provides information material for travellers and consumers, covering dietary precautions and such measures as heat treatment of milk and derived products. Currently WHO is prepar- ing guidelines for the integrated surveillance of brucellosis, and promoting research on new brucel- losis vaccines for both humans and animals. • Dr Ottorino Cosivi is o Scientist with the Zoonotic Diseases Unit, Division of Emerging and other Communicable Diseases SuNeillance and Control, World Health Organization, I 2 I I Geneva 27, Switzerland. Dr Aristorhos Seimenis is Director of the WHO Mediterranean Zoonosis Control Programme, P.O. Box 66074, Athens, GR-15510 Greece. 16 World Health • 51 st Year, No. 4, July-August 1998 Brucellosis in the Americas Primo Arambulo Workers preparing food of animal origin in South America. Slaughterhouse workers are at particular risk of contracting zoonoses such as brucellosis. Photo WHO/PAHO/C. Gaggero Of the various species of the brucel losis bacterium, Brucei'la melitensis is the most likely to cause serious illness in humans. Next comes B. suis, then B. abortus, then B. canis. The main mode of transmission of brucellosis to humans is consumption of conta- minated milk and cheese. Brucellosis spreads through the population where contaminated food is sold. The different stages of the disease are difficult to diagnose, and in areas where brucellosis (particu- larly the bovine type) recurs regu- larly in animals, infection is often transmitted in asymptomatic form. The main countries in the Americas affected by this foodborne disease are Argentina, Mexico and Peru. In 1995, a total of2699 cases of human brncellosis were reported in Mexico. In 1996, there were 3362 cases : an increase of approximately 20%. The Mexican States most affected are Guanajuato, Coahuila, Durango and Nueva Leon. In Argentina, 496 cases of human brucellosis were reported in 1995 and the number increased further in 1996, to stand at 565. The provinces most affected are those with the largest goat population: Catarnarca, Mendoza, Salta and San Luis. In Peru, brucellosis recurs regu- larly in the departments of Ancash, Lima, lea and El Callao, where there are epidemic outbreaks. Vaccination of goats has brought about a consid- erable reduction in cases among humans, but vaccination programmes which do not reach most of the target animal population or are not carried out every year lead to new outbreaks. In countries where the disease in animals has been brought under control, it can reappear sporadically in individuals who acquire the infec- tion from abroad, usually by consum- ing illegally imported and unsafe animal products. It also occurs from time to time in occupationally ex- posed groups such as farmers, vet- erinarians and laboratory and slaughterhouse workers. In North America, efforts to eradicate brucellosis have been successful in Canada which has been free of the disease since 1985. In the United States, 141 herds were found to be infected in 1996, of which only 45 were still under quarantine at the end of that year. The United States hopes to eradicate the disease by the end of 1998, but this might not be possible because of the difficulty of vaccinating bison, which live in the wild. Annual incidence of brucel- losis in humans in the United States has been below l 00 cases since 1996. • Dr Primo Arambulo is Coordinator of the Veterinary Public Health programme at WHO's Regional Office for the Americas/Pan American Sanitary Bureau, 525, 23rd Street NW, Washington, DC 20037, USA World Health • SlstYear, No. 4, July-August 1998 17 lnf luenza - preparing for a . 21 st century pandemic Destroyed poultry is placed in plastic bogs ready for disposal. The Hong Kong authorities decided to take this precautionary measure when, in December 1997, chickens were found to be infected by on influenza virus responsible also for the disease in humans. Photo WHO/K Stohr O's global surveillance cti vities first identified a human infection with the avian influenza virus A(HSNl) in Hong Kong in mid-1997 at one of the Organization's collaborating centres. The HSNl was not previously known to cause infection in humans. The possibility that the outbreak heralded a global influenza pandemic has not materialized, but the threat of an influenza virus more easily transmit- ted between humans remains. Sooner or later such a pandemic may occur, and history shows that it must be taken with the utmost seri- ousness. The WHO Network for Global Influenza Surveillance, which involves 110 national influenza centres, maintains constant vigilance. New influenza viruses to which nobody is immune may cross the barrier from animals to humans at unpredictable times. These events may result in local epidemics, but a few lead to global pandemics. Influenza was first described by Hippocrates in 412 BC and about 30 possible pandemics have been docu- mented in the last 400 years. Three have occurred in this century - in 1918, 1957 and 1968. The 1918 pandemic of what was known as Spanish flu was by far the most devastating, killing more than 20 million people worldwide be- tween 1918 and 1920. The virus is believed to have originated in swine. The pandemic occurred because the new virus was easily transmitted from person to person. Birds and poultry in particular are other sources of influenza viruses, and in Hong Kong the chickens had been infected by the HSNl virus from an animal source or reservoir in nature that is still to be identified. Then then virus was transmitted from poultry to humans. Significant person-to-person trans- mission does not seem to have taken place. As a precautionary measure during the outbreak, the Hong Kong authorities destroyed poultry flocks to eliminate the risk of further ani- mal-to-human transmission, and a team of experts organized by WHO took more than 1800 samples from birds and animals of 16 species to identify the natural reservoir of the virus and the extent of its spread in animals. The results are still pending. WHO has for many years played a leading role as a watchdog on the look-out for a pandemic, active in global influenza surveillance and in vaccine preparation. Every February, experts review results from WHO's influenza network and make a recommendation on the antigenic composition of the next year's influenza vaccine, which WHO transmits to health authorities and vaccine manufacturers. Although the date of the next influenza pandemic cannot be pre- dicted, the strong likelihood of its arrival means that emergency re- sponse plans have to be prepared in advance. WHO has created a Task Force on Influenza whose members include the directors of four main collaborating centres in Australia, Japan, the United Kingdom and the United States, WHO staff, and representatives from three of the 110 national influenza centres which collaborate with WHO on surveil- lance. The Task Force is developing a plan for the global management and control of a pandemic. The plan includes the promotion of high- growth seed virus for vaccine, the facilitation of vaccine production and international distribution, and the dissemination of information and support to national health authori- ties. It calls for each of these author- ities to develop its own emergency response to a pandemic. The A(HSNl) outbreak in Hong Kong was the first one in which WHO pandemic planning was used, with the step-by-step collection of information necessary to decide whether or not a new vaccine was required. The outbreak also pro- vided the opportunity to adjust the plan in line with experience. In this way the scientific information neces- sary to make rational decisions on influenza control is being steadily accumulated. • from The World Health Report 1998 - Life in the 2 I st century: a vision for all, WHO, 1998, p.59 18 World Health • Sl stYear, No. 4, July-August 1998 Improving the health of nomadic people - the example of cystic hydatid disease (alum N. L. Macpherson Although a low-intensity programme continues today it is felt that further reduction of the disease is in the hands of the Turkana themselves. Between 50 and 100 million people in the world today, chiefly in Asia and Africa, lead a nomadic life. The areas in which nomadic people live have low popu- lation density and may not have roads or telecommunications. Their migratory lifestyle means that no- mads are unlikely to have access to permanent educational, medical, and veterinary services or to trained personnel, and they may not have safe and sanitary water supplies. Because of these factors, and because many nomadic people live and work close to animals , they are highly exposed to zoonoses - diseases shared by vertebrate animals and humans. The Turkana District The Turkana people in north-western Kenya are nomadic pastoralists who practise transhumance, moving with their herds in search of pasture throughout a vast semi-desert region known as Turkana District. Their migrations follow seasonal rainfall patterns allowing them to make use of vast tracts of seasonally produc- tive land. There are about 65 OOO Turkana people, and they keep a range of animals including sheep, goats, cattle, dromedaries and donkeys. Dogs are kept mainly for protection and domestic help. Animals repre- Turkana people at a water hole dug in a dry river bed in north-western Kenya. Animals may infect such sources of water and thus transmit zoonoses to man. Photo C Macpherson© sent wealth and prestige and are used as gifts to cement friendships and marriage. Milk is the main con- stituent of the Turkana people's diet, on occasion flavoured with blood, and nowadays increasingly supple- mented with millet, sorghum and maize. Few animals are slaughtered for meat, and there are not many abattoirs in the region; when slaugh- tering does take place, it is usually done at home, and the offal , which is often infected, is fed to the dogs. The lack of veterinary facilities means that meat inspection is rarely carried out and that the dog popula- tion grows without systematic con- trol. Most people share drinking- water supplies with their animals, which include a large number of dogs. All these factors help the trans- mission of a small tapeworm called Echinococcus granulosus, an intesti- nal parasite whose adult stage devel- ops in dogs after they eat the larval stage found in hydatid cysts which grow in the organs - particularly the liver- of cattle, sheep and goats. The dogs shed the eggs of the para- site in their faeces , which in turn infect humans and domestic animals via contaminated drink or food. The eggs contain embryos called onco- spheres, which become trapped in the liver and slowly develop into hydatid cysts, whose removal requires surgery. Turkana has a higher prevalence of cystic hydatid disease than almost anywhere else in the world. This was not realized until the 1960s because patients receiving treatment at the hospitals come from so far away. When eventually it was noticed that a high proportion of these patients World Health • SlstYear, No. 4, July-August 1998 were from the same district, studies were made, and in the mid- l 980s community-based ultrasound sur- veys were carried out. They showed that prevalence was 5.6%, and reached 12% in those aged 35 years or more. The data also showed that almost three times as many women had the disease as men. This was thought to be due to the closer con- tact women in this community have with dogs, which stay around the home during the day while the men and boys are away, and are used to lick the babies clean. Close contact with infected dogs is an important factor, since in hot climates the eggs cannot survive for very long outside a human or animal body. A high prevalence of cystic hydatid disease has also been recorded among other nomadic people in North Africa, the Eastern Mediterranean area and China, where similar socioeconomic condi- tions exist. In Alaska, where no- madic Eskimos were settled, the disease was found to increase be- cause of the accumulation of dog faeces around the towns. In cooler climates eggs may survive for months, making the chances of environmental transmission even greater than in Turkana. Pilot control programme In 1983 a pilot control programme was started in the Turkana District which has decreased the incidence of the disease in the control area. The main strategy was to reduce infec- tion in dogs. To do this, educational information was communicated, by means of songs, poems and discus- sions, about how the disease was transmitted. It focused in particular on discouraging the customary practice of cutting the hydatid cysts out of the liver and lungs of slaugh- tered animals and feeding them to the dogs. Stopping this practice alone, thereby breaking the life cycle of the parasite, can drastically re- duce the prevalence of the disease. The enlarged abdomen in these children indicates the presence of hydatid cysts. Photo C. Macpherson © Other control measures used in Turkana included reducing the stray dog population and changing the way owned dogs were treated. Praziquantel, administered in a single dose, completely frees a dog from infection, but the drug is very quickly metabolized, so reinfection can occur as early as the following day. Thus regular deworming treat- ments are necessary if the dogs are to be kept worm-free by this means. The timing of such events took advantage of seasonal migrations and cultural events. Weddings are held mostly in the wet season, so drugs could be administered to the dogs during this period when more animals are slaughtered for food. In the dry season, when fewer animals are slaughtered, the interval between drug administration could be in- creased. 19 During the dry season people and animals concentrate around the few permanent water holes, and contact was made with people at such points, to explain disease control and discourage the practice of feeding cysts to dogs. However, this period is more stressful for the population - not only are food supplies at their lowest but animals have to be moved to and from water and grazing sites which become increasingly far apart as the dry season intensifies. So, although access to the population is easier, people are less ready to give their attention to matters that seem less urgent. Dog-control programmes and drug administration programmes are not easily sustained and can require external aid. Although a low- intensity programme continues today it is felt that further reduction of the disease is in the hands of the Turkana themselves. If dogs are not fed cysts they will not become infected with the adult worm and will not produce the eggs which then infect humans and domestic animals. If cysts in the viscera of livestock are identified and destroyed this would prevent transmission of the disease and, over time, eradicate it. • Or Ca/um N. L. Macpherson is Director of Research and Professor of Parasitology, Windward Islands Research and Education Foundation, P.O. Box 7, St George's, Grenada, West Indies. 20 World Health • SlstYeor, No. 4, July-August 1998 When does a pet become a health hazard? Marcelo de Menezes Brandiio & Marilia Anselmo Viana da Silva Berzins Possibly the most important factor in the control of zoonoses is education, mainly directed at children, since they will spread the message to older people about sensible care for pets and good hygiene. live in an area of 1500 square kilo- metres. Not surprisingly, the city has a great many social and eco- nomic problems, since many areas have poor housing, few schools, high unemployment, and often inadequate public transport. Yet it is the principal consumer market and provider of services in Brazil. It is essential that children are taught how to care for their pets and maintain good hygiene. Photo WHO/PAHO/C. Gaggero The city 's Centre for Control of Zoonoses was created in 1973 under the City Office of Health, and its principal task was the control of rabies - the frightening disease transmitted from rabid animals to humans, for whom it is almost in- variably fatal. At that time there was a serious epidemic of animal rabies in the city, with frequent human victims too, so the Public Health Office launched a major control campaign. Years of hard work rounding up stray dogs and cats, vaccinating them and keeping them under surveillance at last paid off; since 1981 we have had no case of human rabies, and since 1984 no case of animal rabies. Mrs Maria, a childless widow aged 75 , lives in a small three-roomed house in a suburb of Sao Paulo. She shared her home with 32 cats until neighbours called the Centre for Control of Zoonoses to complain of the bad smell. The cats roamed in other people's houses looking for food; most of them had skin diseases such as scabies, and several lay dead inside her home. After some discus- sion, most of her pets were sent into the care of the Animal Protection Associations, with the owner's agreement, but she was permitted to keep several of them, and these were very soon restored to good health. The area where the cats lived was completely cleaned and the house is once again spick and span . Feline overcrowding no longer poses a health risk to Mrs Maria and her neighbours. This little episode is just part of our centre's daily routine. Sao Paulo is the biggest city in Brazil, the second largest in Latin America and by some reckoning the third largest in the world. Its 10 million inhabi- tants come from all parts of Brazil and from many other countries to International recognition The Centre continues to keep a careful watch for any recurrence of urban rabies, but it is also engaged in the control of other urban zoonoses - diseases transmitted from animals to humans - such as leptospirosis and leishmaniasis. It is also responsible World Health • SlstYeor, No. 4, July-August 1998 The Centre for Control of Zoonoses in Sao Paulo worked tirelessly rounding up stray dogs and cats and vaccinating them against rabies. Since 1984 no further cases of rabies have been registered in humans or animals. Photo WHO/ PAHO/ C. Gaggero for the control of insect vectors of diseases such as malaria and Chagas disease. Since 1985 we have been the National Reference Centre for urban zoonoses, and since 1994 a WHO Collaborating Centre - wel- come confirmation that we have been nationally and internationally recog- nized for our professional training and research in new techniques of zoonoses control. Pets mean companionship for a great many people in the city, espe- cially when they have few social relationships. People give their pets names, share their food and even their beds with them. Pets become members of the family, with the big advantage that they offer humans unconditional affection, never criti- cize and are always present, in times of happiness or of sadness. At our Centre we stress the im- portance of controlling zoonoses, but we also know that the association between human beings and animals has existed since the world began and it does not depend on social standing, wealth, intelligence or age. Unfortunately that association some- times surpasses the bounds of com- mon sense and can therefore pose public health risks. For example, we have been wrestling with the prob- lem of a wealthy family who keep almost 400 dogs in their house with very poor standards of cleanliness and sanitation. The animals are born, live and die haphazardly within the house; they even eat each other - this in a smart residential area of Sao Paulo, despite constant complaints from neighbours. Our Centre can only act within the laws and we often face long delays before judgement is given. Nor do magistrates give a ruling about where the animals can be sent, so we have to invest money and effort in solving such problems. This does not always give the neighbours the satisfaction they want! Elderly owners Brazil's population is ageing, as is that of other countries, so many of our duties concern people aged over 60 and their relationships with their pets. Many of these people have limited spending power, but may have up to 20 or even 100 animals (usually cats or dogs). They tend mostly to be single or widowed women living on their own. Our medical and veterinary agents and social workers are always made welcome when they make house visits, and can usually resolve whatever problem has arisen . All pets have to be vaccinated and we try to reduce their numbers to a reason- able level. The hardest part is per- suading these elderly owners to part with some pets which they often regard as family members. Mr Agenor is 67 years old, has never been married and has no chil- dren. His life revolved around 18 cats and four dogs. Our visiting team, with the help of his cousin, persuaded him to Jet 12 of the cats be rehoused with friends, neighbours and Animal Protection Associations. He has kept the remaining cats and the dogs, all have been vaccinated and, after a few lessons in pet man- agement, he continues to live hap- pily with his companions. 21 While we know the need for control of zoonoses, we are aware that the most important factor is education, mainly directed at chil- dren. It is they who can most easily sow the seeds of sensible caring for pets and good hygiene. The Centre for Control of Zoonoses has in- vested heavily in education, as we seek to help people to understand what keeping pets and other animals really entails in order to avoid health hazards. Our activities also serve to reduce the number of cats and dogs abandoned to fend for themselves in the city streets. • Animals offer companionship to elderly people who live on their own. Doctors, veterinarians and social workers visit homes to resolve problems as animals and people live together. Photo WHO/ PAHO/ C. Gaggero Dr Marcelo de Menezes Brandao is Director of the Sao Paulo Centre for Control of Zoonoses and Ms Marilia Anselmo Viana do Silva Berzins is a social worker at the Centre. The address is: Rue Santa & Eulalia, no 86 - Santana, Sao Paulo, Brazil CEP: 0203 1-020. 22 World Heolth • 51 st Year, No. 4, July-August 1998 Zoonoses and the immune system Ashley Robinson The benefits of pet ownership can outweigh the risks of infection, provided that common-sense pet care guidelines are followed. Many people today have a weakened immune system as a result of chronic infec- tion or because they have received powerful drugs during cancer treat- ment or have undergone organ transplants. The problem is set to become more acute in the future as the proportion of elderly people, who are more likely to develop cancer than young people, continues to grow. Naturally, anyone suffering from a disorder of the immune system must take care to avoid unnecessary exposure to disease, but to what lengths should they go? Should they, as some have sug- gested, part with their pets or change their job if it involves potential contacts with zoonotic agents? Pets and the sick: a dilemma "People come to visit but they can only stay an hour or so and then they have to leave. My cat, she's always there". These words from an HIV- infected person point to a dilemma faced all too often by people whose immune system may be failing to make the normal response to the many infectious agents encountered in daily activities. Well-meaning friends, health care providers and even physicans may advise those infected with HIV or suffering from other immune disorders to get rid of their pets The risk of catching o disease from a pet is considerably reduced if animals are checked by a veterinarian and ii certain rules of animal hygiene are respected. Photo WHO/PAHO/C Gaggero because they are potentially a source of disease. However, recent studies in the USA have shown that there is little difference in the levels of pet ownership between the HIV-infected and the rest of the population. This suggests that, to a large extent, the advice is being ignored, probably because for many the unconditional affection and companionship offered by pets are hard to do without. When people fall sick, or are unable to work, when even their best friends may desert them, the psychological benefits of pet ownership may often outweigh the risks of acquiring a zoonotic infection. In view of the dilemmas that can arise, it is impor- tant to know what the real dangers are and what steps can be taken to minimize them. The major zoonoses that HIV- infected and other immunodeficient persons acquire are: (a) Enteric (intestinal) infections that may result in life-threatening diarrhoea such as salmonellosis, campylobacteriosis, and cryp- tosporidiosis. These infections are most likely to be either water- borne or acquired indirectly through food. On occasion, however, they are acquired directly from animals, especially if these have diarrhoea. (b) Systemic infections which in- volve the body as a whole. Toxoplasmosis, tuberculosis, cryptococcosis, Q fever and cat scratch fever are all examples of this type of infection which may lead to encephalitis (inflamma- World Health • Sl stYear, No. 4, July- August 1998 23 Pet selection and animal handling guidelines for the immunosuppressed l . Before purchasing a new animal, contact a veterinarian for information and help. It is best to avoid stray animals as wel l as puppies, kittens , reptiles and monkeys; these are more likely to carry infections. Neutered animals (castrated or spayed) are safer as they are less likely to roam. 2. Domestic animals have their own immunodeficiency viruses such as the feline leukaemia virus. As a result, infected animals can be at greater risk than others of acquiring zoonotic infections Cats , for example, should be tes ted and, if negative, vaccinated before adoption or purchase . Animals can also be tested for zoonotic infections before purchase, but a negative test is no guarantee that a subsequent infection will not occur. Measures to avoid infections are likely to be more effective in the long run. 3. After purchase, keep the animal healthy and clean, as sick animals are more likely to spread infection via faeces, urine or saliva. Consult a veterinarian for diagnosis and treatment, as wel l as ensuring that the appropriate vaccinations ore given. 4. Feed pet animals and birds the pet foods available in shops, or cooked foods Do not feed them raw or undercooked meat or eggs, or unpasteurized milk, and do not let animals drink from a toilet. 5. As a general rule keep animals indoors; when outs ide, keep them on a leash or tether. 6. Keep animals free of parasites, including fleas and ticks, and keep their sleeping and feeding areas clean. 7. Keep claws short to avoid scratching. In extreme cases the claws can be removed entirely. Animal-inflicted iniuries should always receive immediate first aid, and a doctor shou ld be consulted. 8. Always wash hands thorough ly after handling ani mals and weor disposable gloves when cleaning up faeces or vomit or when disposing of litter. The agent Toxoplosmo g ond ii takes about 48 hours to become infectious in cot faeces, so litter should be removed daily Similar precautions should be taken when working w ith livestock, and care shou ld be exercised when dealing with animals which have diarrhoea (particularly when they are young) or when hand ling animals th at have recently been aborted. tion of the brain) and/or pneumo- nia. Most of these agents can cause illness in animals, but the infected animal may appear to be quite healthy. Zoonotic diseases are most likely to be found in younger animals, animals under stress or living in crowded condi- tions such as kennels, and out- door animals which hunt for part of their diet. before drinbng it. Thj s can be done by boiling it. Finally, it is worth remembering that the human strain of tuberculosis is easily transmitted to dogs. Therefore if a dog is diag- nosed as having this disease there may be a human source of infection in the immediate environment. A helping hand In some places, local organizations have been formed to provide infor- mation and assistance to HIV- infected pet owners. Volunteers can be of enormous help: they can change litter boxes, clean fish tanks and bird cages, walk dogs, assist with flea control in the home, take care of pets when the owners are hospitalized and, if necessary, arrange for their adoption. Tuberculosis and HIV There are several different types of tuberculosis that affect humans, and tuberculosis is a relatively common illness in HIV-infected people. Although birds are occasionally infected with the avian type, humans usually acquire this strain from their immediate environment rather than from an avian source. A marine type of tuberculosis has occasionally been transmjtted to people with HIV infection, usually from a contami- nated aquarium. The bovine tuber- culosis type is no longer a major cause of infection in industrialized countries. The situation in develop- ing countries is more problematic; where the prevalence of both HIV and tuberculosis is high, there is a real risk that people could be in- fected with tuberculosis from their cattle. Where systematic pasteuriza- tion is not practised, it is therefore very important to sterilize milk A moment of tenderness is shared by this man and his pet. The association PAWS {Pets are Wonderful Support), based in California, USA, provides volunteers who take care of all aspects of pets' hygiene for people with HIV/AIDS The emotional support provided by pets far outweighs the risk of disease. Photo WHO/PAWS/P Baucher In conclusion, pets can be good for our health and emotional well- being. For those with immune disorders, the benefits of having pets can be especially important. Providing that common-sense guide- lines are followed there are no sig- nificant reasons why these benefits should be denied. • Dr Ashley Robinson is Professor and Clinical Epidemiologist, Middle East Regional Cooperation Proiect, Tufts University/School of Veterinary Medicine, 200 Westboro Road N, Grafton, MA O 1536, USA. The September-October issue of World Health will report (on page 28) on the 8th lntemational Conference on Human-Animal Interaction on "The changing roles of animals in society" (Prague, September 1998). 24 World Health • SlstYeor, No. 4, July-August 1998 Diseases transmitted by pets Bruno B. Chomel Puppies are great companions for children, but they con also be responsible for transmitting rabies. Photo WHO/ PAHO/ C. Go99ero Animals have always played an important part in our societies as a source of food, labour and companionship. In most industrial- ized countries, more than one house- hold in two reports owning a pet of some kind, with dogs, cats and birds being by far the most common choices. Recently, however, in a trend which is particularly marked in North America and western Europe, people have begun choosing pets from a wider range of species. These include not only small rodents and ferrets , but also reptiles, pot- belly pigs and even bats. There exist more than 150 infec- tious or parasitic diseases which can be transmitted from vertebrate animals to humans. Those high- lighted here are mentioned either because they are extremely severe, especially in children, or because they are very common, though often underreported. Transmission by bites and scratches Dogs and cats can be a source of several major zoonotic diseases. Among these, rabies is certainly the most feared, as it is always fatal in patients who do not receive treat- ment. It is estimated that every year more than 50 OOO people worldwide die of rabies. The bite of any pet in countries where rabies is endemic in dogs or wildlife should be reported to the health services, and the animal responsible should be placed in quarantine for at least ten days. Dogs remain the major threat; in recent years , several reports from areas in which dog rabies is endemic have emphasized the role played by very young rabid puppies in human infection. Over the last few decades, post-exposure treatments for rabies have been greatly improved and modern vaccines should now be made more accessible and less expensive in the developing world, where humans are most at risk from rabies. In addition, mass rabies vaccination campaigns aiming at a coverage of at least 70% of dogs, the application of leash laws and the placing in quarantine of animals responsible for bites are essential to ensure that human infection is re- duced. Another disease associated with dog and cat bites is pasteurellosis. This bacterial infection, caused by Pasteurella multocida, is character- ized by a sharp pain where the bite There exist more than 15 0 infectious or parasitic diseases which can be transmitted from vertebrate animals to humans, but owners who look after their pets properly should have little to fear. was received, which the victim only starts to feel some hours after being bitten. The pain is accompanied by redness and swelling, and sometimes the lymph nodes become enlarged. If not treated with appropriate anti- biotics (penicillin or amoxicillin, for example), this infection can lead to severe complications such as tendon or bone destruction. Pasteurellosis infections are particularly common following cat bites. Cat scratches are also a source of human infections, especially in children and teenagers exposed to young kittens. "Cat-scratch disease", caused by a recently identified bacterium, Bartonella henselae, is typically a benign, subacute, re- gional lymphadenitis (inflammation of the lymph nodes) in which the agent responsible is introduced through the skin . In people whose immune system has been weakened, it causes bacillary angiomatosis, a life-threatening vascular disease in which tumours are formed from blood cells. Domestic cats may be healthy carriers of the organisms and can be infected for up to several months. The disease is transmitted from cat to cat primarily by fleas; as a result, flea-infested stray cats are more likely to be a source of human infection. World Health • SlstYear, No. 4, July-August 1998 25 Children with their favourite kittens. Cot scratches con be a source of human infection if the cots themselves have been exposed to in fection. Photo WHO/PAHO/C Goggero Free-roaming or feral dogs ore more likely than well-groomed pets to come into contact with a variety of pathogenic agents that they con transmit to humans. Photo WHO, by courtesy of Dr H. Motter Other modes of transmission In countries where plague (caused by Yersinia pestis) is endemic, free- roaming pet cats can become in- fected or carry infected rodent fleas that pass the disease on to humans. Cats are very susceptible to plague and develop bubonic, pneumonic and septicaemic plague. Several human cases of bubonic and pneu- monic plague in the USA have been associated with exposure to pet cats. Most diarrhoeal and gastro- intestinal illnesses are acquired through consumption of tainted food items, but pets, too, can carry infec- tious agents, such as Campylobacter or Salmonella. Puppies or kittens with diarrhoea pose the greatest zoonotic risk. It should be common sense to prevent infection by wash- ing one's hands after contact with pet animals and prior to eating. Reptiles are carriers of a wide range of Salmonella species. Recently, many more iguanas have been pur- chased as pets, particularly in the USA, and this trend has been charac- terized by several severe, even fatal, Salmonella cases in young children . Pet turtles also are a major source of Salmonella infection, causing out- breaks in many countries worldwide. Pet rabbits are rarely a source of zoonotic diseases. Rodents, on the other hand, transmit a wide range of viral infections, including hanta- virus. This is a serious disease which produces flu-like symptoms together with kidney deficiency, or even kidney failure. This disease can also cause an acute respiratory distress syndrome. Another acute viral infection which can be very severe in children is lymphocytic choriomeningitis (LCM), leading to a flu-like illness followed by neuro- logical symptoms, such as aseptic meningitis. In both the USA and Germany, outbreaks of LCM have occurred in children contaminated by pet hamsters. Outwardly healthy rodents can be carriers of the virus. In any case, it is important to re- member that non-domesticated rodents should not be kept as pets. Parasitic infestations are com- mon in young pets. Cats are the definitive hosts of the agent of toxoplasmosis, Toxoplasma gondii, which is a common infection in humans, especially in developing countries or countries where meat is traditionally consumed under- cooked. Most infected persons may not show clinical signs, but if women are infected during preg- nancy, this can result in abortion, stillbirth, or congenital defects such as mental retardation. Pregnant women should either not clean cat litter boxes at all or do it every day to prevent the Toxoplasma eggs from maturing. In developing countries, puppies and kittens may be heavi ly infested with roundworms (Toxocara canis or T.cati) that they shed into the environment. Young children who are playing outside may be infected by ingesting eggs present in the soil or on contaminated hands or other objects. One of the complica- tions of these infections is ocular larva migrans which causes strabis- mus, failing vision and eye pain. There are two main preventive measures: pets should be dewormed regularly, particularly when young; and they should be prevented from defecating in sandboxes where children may play. Pet birds, especially psittacines (such as parakeets, cockatiels and budgerigars) frequently harbour Chlamydia organisms, shedding them in their faeces and spraying them as aerosols. Humans acquire psittacosis by inhalation of infec- tious aerosols. The disease is an atypical pneumonia with fever, headaches, muscle pain and short- ness of breath accompanied by a non-productive cough. Treatment is based on the use of antibiotics, such as doxycycline, and in industrialized countries most imported psittacine birds receive a preventive antibiotic cure for three to four weeks. In summary, people need to be aware of the health risks associated with pet ownership, but it should be emphasized that zoonotic diseases are usually quite rare. Owners who look after their pets properly, ensur- ing that they are well nourished, correctly vaccinated and regularly examined by a vet, should have little to fear. • Dr Bruno B. Chomel is Associate Professor of Zoonoses, Deportment of Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, USA. 26 World Health • SlstYear, No. 4, July-August 1998 Dogs and Aboriginal health in Australia Bart Currie Living in a remote Aboriginal community in Australia, this dog carries the disease scabies, which puts young children at special risk . Photo B. Currie © The question in any communif}t where dogs interact with humans is the degree to which infections and related nutritional problems are the result of dog-to-human interaction rather than human- to-human interaction or human interaction with the rest of the local environment. Mortality rates in the 2~0 year age group are up to 10 times higher for Aboriginal people than for other Australians, and life expectancy is 10-20 years lower. There are many remote Aborigi- nal communities scattered across central and northern Australia. These communities have popula- tions ranging from less than 100 to a few thousand, frequently living in harsh conditions. Overcrowding is common, and sometimes 20 or more people may share a single house with a poor water supply and inade- quate sanitation. Dogs, disease and humans Dogs are often numerous in Aboriginal communities. They live a semi-domesticated existence, scrounging for food around the houses and defecating nearby. The relationship between people and dogs is partly one of companionship but involves other more complex cultural factors. Since the mid- l 980s a range of "dog programmes" have been intro- duced in Aboriginal communities in order to limit the size of the canine population and improve its health. Various combinations of dog control and treatment have been applied, including dog sterilization, contra- ception, "euthanasia" and the use of anti-parasitic drugs. For a number of reasons the programmes have not always had a particularly unified character: sometimes they have been set up at the behest of the local com- munity, sometimes not; funding has come from a variety of government and non-government sources; imple- mentation has often been on an ad hoe basis and sometimes the initia- tives have not been maintained. Indeed, there was actually an in- crease in dog numbers fo llowing certain earlier programmes which failed to tackle dog population control. The more sustained programmes with better funding and planning have clearly brought about a sub- stantial improvement in the health of dogs in Aboriginal communities. What remains unclear, however, is whether these programmes have had any significant impact on human health. It was initially hoped that the dog programmes would prove par- ticularly beneficial to the health of children because of their close contact with dogs, but this has yet to be confirmed. Concerns have been raised that the assumption that dog programmes improve children's health could be used to justify redi- recting health resources away from child health programmes towards dog health programmes. There are a number of bacteria, viruses, fungi and parasites that can be transmitted from dogs to humans. The question in any community where dogs interact with humans is the degree to which infections and related nutritional problems are the result of dog-to-human interaction rather than human-to-human interac- tion or human interaction with the rest of the local environment. The classic zoonoses transmitted from dogs to humans are hydatid disease (from a dog tapeworm), World Health • SlstYeor, No. 4, July-August 1998 An aboriginal village in northern Australia. Programmes for ensuring better health for dogs should be provided in addition to essential health infrastructure programmes such as child health core, and adequate housing, wafer supply and sanitation. Photo Ponos/C.Sottlberger © which causes cysts in the liver and elsewhere, and toxocariasis (from dog and cat roundworms), which causes parasites to collect particu- larly in the liver and behind the eye. Hydatid disease does not occur in most of central and northern Australia, and cases of toxocariasis are very rare. Less important but well known zoonoses include a dog lungworm and dog hookworm. Lungworms, which are transmitted by mosquitos, occasionally cause lung nodules in humans. Dog hook- worms, which hatch from dog faeces, produce a migrating itchy skin lesion in humans as their larvae attempt (unsuccessfully) to penetrate beyond the inoculated skin of their host in order to enter the blood- stream. Recently, gastrointestinal and skin infections have been the focus of research into potential zoonotic transmissions from dogs to humans. Transmiss ion of gastrointestinal infections is usually faecal-oral via contaminated food, water, hands, utensils or soil. Flies, too, facilitate the transmission of certain bacteria. Some gastrointestinal parasites such as human hookworms and strongy- loides (nematode worms) are trans- mitted from faeces to the skin via the soil. Skin bacteria and scabies parasites are transmitted directly from skin to skin. For both diar- rhoeal disease and skin disease, extensive epidemiological studies have shown that the most important factors for transmission are house- hold overcrowding, poor san itation and an inadequate water supply. International experience suggests that in disadvantaged Australian Aboriginal communities there will be a high level of human-to-human transmission of infectious diseases. The unknown quantity is the additional burden of infections represented by dog-to-human transmission. The role of human-to-human transmission has been firmly estab- lished for the major microorganisms causing diarrhoeal diseases, includ- ing those transmitted indirectly via contaminated food products and water. However, the role of poten- tial zoonotic infections from dogs has only been adequately docu- mented for a few organisms such as Campylobacter (which can cause gastroenteritis) and certain strains of Salmonella. Even in the case of Campylobacter and Salmonella, however, transmission from dogs represents only a small proportion of the total. There has been consider- able interest in whether the Giardia parasites found in dog faeces are similar enough to those in humans to be transmitted zoonotically. Preliminary molecular genetic studies suggest that the cycles of transmission of Giardia in dogs and humans may not actually overlap to a significant degree. The major skin infections in Aboriginal communities are skin 27 sores (streptococcal), tinea (ring- worm fungus) and scabies. In the case of skin sores, the streptococcal bacteria involved are different for dogs and humans. The fungus responsible for nearly all the skin and nail tinea in Aboriginal commu- nities is specific for humans, unlike some of the tinea fungi seen in southern Australian cities, which are zoonotic from cats and dogs. The animal variants of the scabies mite are generally restricted to animal hosts, and recent molecular genetic studies suggest that the vast majority of cases of scabies in the current epidemic in Aboriginal communities are unrelated to cycles of transmis- sion of the dog scabies mite. Hard choices International experience has pro- vided a wealth of evidence on the role of human-to-human infection in the transmiss ion of diarrhoeal and skin diseases. While many Aboriginal communities have large numbers of dogs (many of them unhealthy) living in close proximity to people, the contribution these dogs make to the infections and related nutritional problems of the community remains unclear. Hard choices have to be made in the light of financial constraints and competi- tion for public health resources, and it should therefore be remembered that child health programmes remain a priority. Routine community- based deworming, coordinated scabies programmes, and education initiatives must come before dog programmes. The issue of unhealthy dogs should not be pursued at the expense of the essential components of community health, such as ade- quate housing, water supply and sanitation. However, given the considerations outlined above, dog programmes in addition to child health and health infrastructure programmes could provide some benefits to humans. • Dr Bart Currie is Associate Professor and Head of the Clinical Unit, Menzies School of Health Research, Darwin, PO Box 4 l 096, Casuorino NT 081 l , Australia. 28 World Health • SlstYeor, No. 4, July-August 1998 Keeping foods of animal origin safe Fritz K. Kiiferstein & Fransois-Xavier Meslin F oods of animal origin constitute a certain proportion of most people 's diet. Food animals help to sustain human life, but there is a negative aspect: a number of diseases can be directly transmitted by contact with animals (living or dead), or indirectly by eating such foods as eggs, meat, poultry, fish, shellfish and dairy products. In- direct transmission of disease can occur in two ways: foods may serve as a medium which allows bacterial pathogens to grow, or they may merely act as a passive vehicle of pathogens (as occurs with parasitic and viral diseases). Many bacterial diseases due to microbes originating from food animals have emerged during the past 20 to 25 years. Inappropriate hygienic practices at animal hus- bandry, slaughterhouse and food processing levels are some of the factors which facilitate the multipli- cation and spread of these bacteria in food. Outbreaks of disease in hu- mans are then all too likely. Non- typhoid Salmonella and Campylobacter are the two most important organisms in this context. Salmonellosis in particular has increased tremendously over the past two to three decades, in many cases due to an emerging serotype called Salmonella enteritidis. Poultry meat, eggs and food containing eggs are often the predominant sources of this pathogen. Multidrug-resistant Salmonella typhimurium DT104 has been linked to poultry, a variety of meats and meat products, and unpas- teurized milk. Campylobacteriosis has increased so much over the last 10 to 20 years that it is now the leading foodborne disease in several industrialized countries; again, the main vehicles for its transmission are poultry and unpasteurized milk. Another emerging pathogen which is frequently transmitted by food of animal origin is enterohaem- orrhagic Escherichia coli (especially E.coli 0157:Hl). First identified in 1982 in the USA, this organism has caused serious outbreaks in several parts of the world, and beef has often been the vehicle of transmission. The largest reported outbreak so far, in Japan in 1996, affected more than 9500 people (mainly schoolchildren) and caused 11 deaths, this time probably as a result of eating radish sprouts. A particularly dangerous pathogen, it affects the kidneys in about 10% of infected patients, leading to the life-threatening haemolytic uraemic syndrome. Examples of parasitic and viral diseases which are transmitted by foods of animal origin include: • toxoplasmosis (caused by a protozoa), trichinellosis (caused by a nematode parasite) and cestodiasis (a tapeworm) infec- tion, as a consequence of eating raw or undercooked meats; • nematodiasis and trematodiasis (caused by a parasitic fluke) , as a consequence of eating raw or undercooked fi sh or shellfish; • viral hepatitis A and E, through eating raw or undercooked shell- fi sh. Human infections caused by food- borne parasites or viruses are very common. Toxoplasma gondii in women, for instance, affects three out of every 1 OOO pregnancies, resulting in feta! death, prenatal morbidity or chronic infections. As for trematodes, more than l 0% of the world's population are thought to be at ri sk of being infected. In 1988, a huge outbreak of hepatitis A in Raw foods such as poultry, meal, eggs or milk often contain pathogens which can lead to disease in man. These pathogens can be eliminated by sound technologies and correct cooking practices. Photo WHO/PAHO/A W aak Shanghai, China, affected just under 300 OOO people who had eaten molluscan shellfish (cockles). Public health authorities are also concerned about food of animal origin which contains certain chemi- cal contaminants, whether of envi- ronmental origin or used as veteri- nary drugs to treat or protect farm animals. Mercury is one example of an environmental contaminant; while it is a normal constituent of the aquatic food-chain, contamination of water has led to high, toxic concen- trations of mercury in shellfish, resulting in serious ri sks to human health. Drugs used in veterinary medicine and animal husbandry, if not administered under approved conditions, may lead to unwanted residues in food of animal origin and therefore pose health hazards. Marine biotoxins such as scom- brotoxins, ciguatoxins and phyco- World Health • SlstYeor, No. 4, July-August 1998 toxins form another category of chemical contaminants which may cause poisoning in people who eat fish. In many countries this is a major public health problem, affect- ing thousands of people annually. Whatever the pathogen or vehicle of transmission, the key means of preventing and controlling biologi- cal foodborne hazards are: • prevention of contamination of food ; • prevention of the growth of (bacterial) pathogens; • prevention of the spread and survival of pathogens. These imply three main measures of protection from foodborne diseases. Three measures of protection Firstly, the hygienic quality of raw foodstuffs at the production level must be improved. Although pro- ducing completely pathogen-free milk, meat, poultry and eggs is possible experimentally, its applica- tion on a large scale is not yet feasi- ble. However, by applying the principles of good agricultural as well as animal husbandry and health practice, and by improving the environmental conditions under which animals are raised, the hy- gienic quality of such raw food products can be improved and spe- cific pathogen-free products (e.g. free of Brucella, Mycobacterium bovis, Cysticercus spp, etc.) can be produced. The quality of water in which fish and shellfish are grown must also be safeguarded; provided it is not contaminated with human or animal faeces, the harvesting of products free from pathogenic bacte- ria and viruses is possible. Even so, it is not possible to exclude certain parasites, such as nematodes. Secondly, food-processing tech- nologies should be applied to pre- vent the spread and survival of pathogens in food. Pasteurization, sterilization and irradiation con- tribute to food safety by reducing or eliminating pathogenic microorgan- isms. In countries where milk pas- teurization is widespread or compulsory, it has been possible to prevent many diseases transmitted through milk. Poultry remains a common source of salmonellosis and campylobacteriosis. It is possible that, in the near future , irradiation of meat and poultry products wi ll play a similar role to that of pasteuriza- tion of milk, although its application on a large scale is not yet feasible. The third and last line of defence is the most critical, and should protect the health of consumers even if the other two fail. This is the education of food-handlers in the principles of safe food preparation. These include professional cooks, persons handling food in catering establishments (including street- vendors ), and those in charge of preparing food at home. The educa- tion of food-hand lers is vital be- cause, in most cases, foodborne diseases stem from: • insufficient cooki ng of food or reheating of previously cooked food; • preparation of food several hours before it is eaten, combined with inadequate storage; • use of contaminated raw food; • cross-contamination in the place where food is prepared; • preparation of meals by infected or colonized people. 29 These three measures of protection equally apply to the prevention of chemical poisoning in food. Here, however, the ro le of food-handlers is much more limited and a bigger role must be played by industry and the food control authorities. Every effort should be made to educate those responsible for prepar- ing food for the family, since cases of foodborne disease are frequently due to mishandling of food in the home, as a result of negligence, ignorance or ingrained traditions and habits. Women in particular should be targeted as they are the ones usually responsible for feeding infants and young children, who suffer high rates of sickness and death caused by foodborne diar- rhoea. Educating children in schools should also be recognized as an effective means of communicating to parents the concept of food safety and implanting the principles of safe food preparation in the minds of future adults. • Dr Fritz K. Koferstein was formerly Director of WHO's Programme of Food Safety and Food Aid. Dr Froni;:ois·Xavier Mes/in is Chief of the Zoonotic Diseases Unit in the Division of Emerging and Other Communicable Diseases Surveillance and Control, World Health Organization, 12 1 1 Geneva 27, Switzerland. Public health authorities are increasingly concerned about microbes that may exist in food of animal origin Photo WHO/ PAHO/ C. Gaggero 30 World Health • SlstYear, No. 4, July-August 1998 Animal·to·man transplants Clara J. Witt & Fran~ois-Xavier Meslin Transplanting organs and tissues from one person to another is by now an almost commonplace practice for treating a variety of medical conditions. Removing the heart from a recently dead accident victim and using it to replace the diseased heart of another person was first successfully achieved in 1967. Today, heart, heart-and-lung and kidney transplants and grafts of other organs taken from donors - alive or recently dead - are routinely carried out by major hospitals around the world. Unfortunately, donations of organs have not kept pace with demand. In France in 1994, for example, 1627 renal trans- plants were performed, but there were approximately 4500 individu- als on waiting lists for donated kidneys. As an alternative to human dona- tion, scientists are now investigating the use of animal tissues and organs. This is called xenotransplantation, from the Greek term xenos, meaning strange or foreign. Non-human primates such as chimpanzees have immunological similarities to hu- mans, but potentially higher risk of disease transmission, as well as animal welfare and conservation concerns, argue against their use. Currently pigs are thought to be the animals most likely to be suitable for xenotransplantation because of the similarity of their organ size and anatomy to those of humans. The principal risk with any transplant, whether from human donors or from animals, is that the imported organ or tissue will be rejected by the new host's immune defence system. Hyperacute rejec- tion, for instance, occurs within minutes of xenografting and can lead to death in the patient. Researchers are trying to overcome such rejec- tion by masking the "foreignness" of grafts in their new hosts. Successful Transplants of organs from human donors are now commonplace, but there is a critical shortage of potential donors. So scientists are assessing the risks and benefits of using cells, tissues and organs from specially bred animals to replace diseased organs in human patients. clinical trials have already used antibody-treated fetal pig neurons (a masking technique to trick the host body) as a means of treating patients with Parkinson disease, and transgenic pigs have been specially bred whose cells express more human-like proteins. A United Kingdom report on the use of animals to produce organs for transplantation commented that "some degree of genetic modifica- tion is ethically acceptable providing that there is a concomitant benefit to humans and that the pig neither suffers unduly nor ceases recogniz- ab ly to be a pig." Researchers are also acutely alert to the risk of any known or unknown infectious agent passing to humans from transplanted cells, tissues or organs of porcine origin. The ethical dilemma Beyond the purely medical problems are important issues of public per- ception of xenotransplantation, since the use of animal transplants could conflict with people's beliefs or ethical norms. While some peo- ple might welcome this technology as a demonstration of modem med- ical capability, others might utterly reject the notion of receiving organs from another species. In some religions it is seen as wrong to ac- cept human-to-human transplants. Some cultures consider the pig an "unclean" animal and would not accept organs from pigs, though they would accept them from certain other animals. In some cultures animal tissue might be thought to influence the soul or spirit of the recipient and therefore be unaccept- able. In October 1997, WHO invited 25 specialists from different disci- plines, including microbiology, immunology, veterinary science, ethics, religion and law, to a Con- su ltation on the feasibility and ac- ceptabi lity of xenotransplantation. They agreed that this technique "holds potential for clinical applica- tions" and considered that the use of transgenic, cloned or otherwise genetically modified animals as a source of cells, tissues or organs was acceptable, as long as the health of humans was protected, human dig- nity was respected, and animal welfare and identity were main- tained. They added that "public acceptance should not be assumed," and stressed that policy-makers in this field must take account of peo- ple's ethical, social and religious perceptions and attitudes, as well as each nation 's legal norms. • Dr Clara). Witt, a veterinarian specializing in preventive medicine and laboratory animal science, is currently working for the Bacterial Diseases Unit and Dr Frant;:ois-Xavier Mes/in is Chief of the Zoonotic Diseases Unit, both in the Division of Emerging and other Communicable Diseases Surveillance and Control, World Health Organization, 12 l l Geneva 27, Switzerland. World Health • SlstYear, No. 4, July-August 1998 31 WHO publications Publications con be ordered from Distribution and Sales, WHO, 1211 Geneva 27, Switzerland. Combating a brutal practice Female genital ~u!ilation has been ~ractised for more than 2000 years. At least 130 m1ll1on women and girls alive today have undergone the procedure. Yet although female genital mutilation (sometimes called female circumcision) is so common in some parts of the world - and leads to serious health problems - little is known about it outside the communities where it takes place. Female genital mutilation - an overview provides the information needed to understand both the social importance of the practice and the dangers it presents to the women and girls who undergo it. The book explains what the different types of female genital mutilation involve, what mental and physical complications result, and what research needs to be done to put an end to the practice. Female genital mutilation - an overview does not make for easy reading. It describes a brutal and humiliating practice that has been condemned by international agreements and national governments. The book makes clear why, for the sake of all the women at risk, female genital mutilation must be stopped. Female genital mutilation - an overview {ISBN 92 4 156 191 2) costs Sw.fr. 26-/US $23.40 {Sw.fr 18 .20 in developing countries). Veterinary drug residues in food Many animals are given drugs in varying quantities and for various reasons, but just what effect is there likely to be on humans who eat food that comes from those animals? The question can be worrying, and a joint expert committee of the Food and Agriculture Organization of the United Nations and WHO meets regularly to evaluate available data and make recommendations on maximum safe levels of veterinary drug residues in food. The latest report of the committee evaluates data on a variety of veterinary drugs - antimicrobials, insecticides and others. Annexed to the report is a summary of the committee's recommendations on these drugs, including acceptable daily intake and maximum residue limits for humans. Evaluation of certain veterinary drug residues in food. Forty-seventh report of the Jo,nf FAO/ WHO Expert Committee on Food Additives {ISBN 92 4 120876 7) costs Sw.fr 19-/US $ 17. l O {Sw fr l 3. 30 in developing countries). In the next issue The September-October 1998 issue of World Health w ill not be devoted to a sing le theme, but wi ll present a variety of topics on WHO's work of fig hting disease and its social causes. There w ill be articles on mental health, the impact of lifestyles on hea lth, men 's health, and gender differences requ iring d ifferent approaches to disease control. • A guide to diagnosing rabies and developing vaccines Laboratory techniques in rabies is a comprehensive guide to laboratory techniques for research and diagnosis in rabies and for the production of vaccine. The fourth edition of this standard reference work has been revised and expanded to take into account the latest experience worldwide. The book has six parts. The first gives a general overview of current laboratory techniques and safety precautions, and summarizes the characteristics of the rabies virus. The second and third parts evaluate a range of different research and diagnostic techniques. The fourth and fifth parts deal with the production of rabies vaccine for use in humans and animals, and show how to assess the safety and potency of vaccines. The final part covers the production of anti rabies serum and immunoglobulin for humans and horses. The annexes give a wealth of practical advice that includes the collection and transport of brain specimens and the calculation of vaccine potency. The book's 40 chapters are written by world-renowned rabies researchers. It is fully illustrated for a clearer understanding of the techniques described. Laboratory techniques in rabies, Fourth edition {ISBN 92 4 154479 l) costs Sw.fr. 115-/US $103.50 {Sw.fr 80.50 in developing countries) Bringing relief to the terminally ill I n_cura~le ~iseas~ causes tens of millions of deaths every year. Although the s1tuat1on 1s not likely to change significantly in the short term, much can be done to relieve the suffering that goes along with this kind of disease. For the terminally ill, even small complaints cause suffering. A cough or a hiccup, which is little more than an irritation to the healthy person, can lead to considerable pain and discomfort in a patient with a serious illness. Symptom relief in terminal illness stems from the report of an expert committee on cancer pain relief and palliative care and addresses the need for guidelines on the management of symptoms other than pain - symptoms such as anorexia, anxiety, constipation, depression, nausea, and intestinal and urinary problems. While many of the approaches to symptom relief involve the use of drugs, simple and effective non-drug measures are also described. The book stresses that family members and appropriate counselling can give invaluable support to the patient. Symptom relief in terminal illness complements WHO's Cancer pain relief which is a bestseller that has been translated into mare than 20 languages. Symptom relief in terminal illness {ISBN 92 4 154507 0) costs Sw.fr. 25.-/US $22.50 {Sw.fr 17.50 in developing countries) Printed in Great Britain by GreenShires Print limited, Kettering, Northamptonshire, England. Photo Keystone/ L. Skaaning ©