Sleeping sickness - re-awakes / by Pierre Cattand

Sleeping sickness-re-awakes by Pierre Cattand Mr Pierre Cattand is Training Officer with the Trypanosomiases and Leishmaniases unit at wHo headquarters in Geneva W ith 50 million people at risk , 36 endemic countries and some 20,000 reported infections every year, sleeping sick- ness remains an important public health problem for Africa. The ex- tent of the problem can be better appreciated with the knowledge that , if untreated, infected individ- uals will die of this disease , more correctly known as human African trypanosomiasis. Precise numbers of its victims cannot be evaluated. The most con- servative estimate would be consid- erably higher than the number of actually reported cases , which is based on very limited surveillance and on infrequent and localised surveys. The African continent has paid a heavy price in the past. On the northern shores of Lake Victoria , in the Congo basin, particularly along the Ubangui, the largest trib- utary of the River Congo , and in the territories lying within the big arc of the River Niger, thousands of people died of the disease early in this century. One of many re- ports states : " ... From the 1st to the 15th February 1918, we surveyed nine villages in the Koumi valley (Central African Republic) and examined 1,243 villagers out of a population of 1,260 and found 722 infected individuals; during that same period we personally wit- nessed 35 deaths due to the dis- ease ." In a 1920 report of the Uban- gui-Shari medical sector, we can read : " ... In this population of 100,000, we examined all the inhab- itants one by one. We found 5,347 sleeping sickness cases , 170 lepers, 159 cases of various mycoses, 13 cases of elephantiasis, ... Sleeping sickness on its own is the cause of one-third of the total mortality in that region." Similar situations 24 WORLD HEALTH , July 1988 have been described in East and West Africa. Today, the increase in the num- ber of patients observed in the same historically endemic areas , the discovery of new cases in places A classic case of sleeping-sickness in Africa. Below: Not invaders from outer space, but a novel trap to catch tsetse flies , which transmit spleeping sickness. Photos WHO and C. Lavessiere © previously free of sleeping sickness, and the large number of suspects found during spot-surveys all sug- gest an important recrudescence of the disease . This is particularly the case in Southern Sudan , Uganda and Chad and, to a lesser extent , in Cameroon, Congo, Cote d'Ivoire and Zai·re. If we ignore past evidence of the disastrous impact of sleeping sick- ness and fail to take immediate ac- tion, it may soon become an un- bearable burden for a great number of African countries. The flare-ups that have recently occurred or are occurring in many parts of the con- tinent demonstrate what can hap- pen when surveillance activities and coverage are reduced. Control and preventive measures must be put into effect now before village com- munities feel the devastating effects of sleeping sickness and once again are forced by the tsetse fly to aban- don their fertile lands. In 1916 in Brazzaville, Dr Eugene Jamot elaborated his preventive guidelines for sleeping sickness which are still valid today. Based on the fact that man is the reservoir for the protozoa Trypanosoma gambiense that cause the disease and the tsetse fly is the vector that transmits it, J amot defined a two- fold objective to control the dis- ease, namely the simultaneous de- struction of the parasite and the vector. He knew that the disease concentrates in local areas and that imported cases from these old foci are the origin of new ones. Conse- quently, as many patients as possi- ble had to be treated in the existing foci and all possible neighbouring areas where the disease could prop- agate itself had to be kept under surveillance. In order to ensure ear- ly diagnosis and eliminate the hu- man reservoir, preventive services have to reach all the people ; they cannot wait for the people to come to them. On the basis of these principles, control and preventive services have worked successfully in the past to contain sleeping sickness. Results obtained by the Trypanoso- miasis Control Mission in Angola illustrate this success. The annual surveillance of 500,000 to one mil- lion persons at risk over a period of 25 years, between 1949 and 1973, has resulted in the number of new cases diagnosed each year dropping from 4,318 to just four. Because of the epidemiological differences between the West and Central African T. gambiense and the East African T. rhodesiense forms of the disease, control of the latter requires a greater emphasis on dealing with the tsetse fly than on active surveillance of the human population. In T. rhodesiense infec- tions, the signs and symptoms are so acute and the evolution of the disease so rapid that patients will seek medical help; well-organized passive detection can therefore be an efficient tool for controlling the disease. This is not the case with gambiense sleeping sickness, a chronic disease whose early signs and symptoms are so mild that they may even go unnoticed. This asymptomatic period- may last for months, and sometimes years. The consequences of reducing surveillance for the gambiense form can be very serious. In one endemic country, the number of surveyed persons was reduced in 1961 from WORLD HEALTH, July 1988 A WHO expert advises health workers in Kenya on strategies to combat the disease. Photo WHO/P. Cattand almost one million to 300,000; as a direct result, the number of new cases rose successively in the fol- lowing three years to 9, 66 and 117. Surveillance was then enlarged to cover 800,000 people and was maintained at that level. Six years later, only four cases were diag- nosed, three of which had, un- doubtedly, been infected outside the country. I could cite many other similar examples. These alarming demonstrations of the potential danger of leaving endemic foci unattended have cre- ated an increased awareness at national and international level, and have activated research to- wards finding better technical solu- tions to prevent and control sleep- ing sickness. The last decade has witnessed the development of several new meth- ods for diagnosing the disease. Field-adapted serological (blood se- rum) assays are now available, while refined parasitology tech- niques enable health workers to confirm a greater number of sus- pects. Parameters defining the stage of the disease can now be de- termined with greater accuracy, us- ing modern laboratory technology and equipment that are well-adapt- ed to field use. A promising new compound known as DFMO is under experiment for patients who do not respond to the classical trypanocidal drugs. Vector control techniques have also improved considerably. Bush clearing has been replaced by effi- cient, simple and inexpensive tsetse trapping methods which are envi- ronmentally safe. We can certainly expect further progress. The specific and sensitive serological tests available today will undoubtedly be made more simple to use. Parasitology techniques will become more efficient and cheap- er. Cerebrospinal fluid analysis will be made easier to perform and drugs will become safer and simpler to handle. However, these antici- pated improvements should not provide an excuse to delay or post- pone indefinitely vital prevention and control activities. This is why, in 1984, WHO launched a programme entitled: "Primary health care approach to- wards the control and prevention of sleeping sickness," aimed at pro- moting national programmes and providing endemic countries with the information and the expertise required to design, set up and maintain such activities. The major objective is to participate with the health authorities of endemic coun- tries in designing and formulating country programmes. The pro- gramme arranges training courses in the new laboratory diagnostic techniques and in vector control methods, makes available technical documentation, and provides a sup- ply line for equipment, material, reagents and drugs that are often complicated to obtain. Finally it of- fers countries the assistance they may need to mobilise bilateral or multilateral support. • 25