Second Regional Seminar on Virus Diseases : Mosquito-borne Virus Diseases (Arboviruses), Manila, Philippines, 6-11 October 1969 : final report

,

-

.,

.

WPRO 0158

SECOND REGIONAL SEMINAR ON VIRUS DISEASES: MOSQUITO-BORNE VIRUS DISEASES (ARBOVIRUSES)

Sponsored by the WORLD HEAL'll! ORGANIZATION REGIONAL OFFICE FOR THE WESTERN PACIFIC

Manila, Philippines 6-11 October 1969

FINAL REPORT

Nor FOR SALE

PRINTED AND DISTRIBUTED

by the REGIONAL OFFICE FOR THE WESTERN PACIFIC

of the World Health Organization Manila, Philippines December 1969

!!.

WPR/416/69

CONTENTS

,.

1. 2.

INrRODUCTION ............................................. JAPANESE ENCEPHALITIS •••••••••••••...•••••.•.•.•••••.••• THE DENGUE-COMPLEX AND CHIKUNGUNYA ••••••••••••••••••••••

1 1 10 20 23 24 26 27/28

3.

4. 5.

. OTHER ARBOVIRUSES ......................................

VECTORS

AND THEIR CONTROL •••••••.•.•••••••••••.•••••.••

" ~

6. 7.

INTERNATIONAL CO-OPERATION AND WHO ASSISTANCE •••••••••• SURVEILIANCE •.••••••••••••••••.•••••••••••••••••••••••• SUGGESTIONS AND COMMENTS ••••••••••••••••••••••••••••••• ANNEX 1 A SCHEr-lATIC ILLUSTRATION OF FACTORS loJHICH INFLUENCE AN EPIDEMIC SIZE OF JAPANESE mCEPliAUTIS ....................... , ......... . LIST OF PARTICIPANTS •••••••••••••••••.•••••••• AGENDA •••••••••••••••••••••••••••••••.•••••••• GROSS NECROPSY FINDINGS IN 100 CASES OF CLINICALLY-DIAGNOSED HAEMORRHAGIC FEVER IN THE PHILIPPINES •••••••••••••••••••••• ARBOVIRUSES NOT YEl' REIATED TO HUMAN DISEASE IN THE WESTERN PACIFIC REGION (WHO). GEOGRAPHICAL DISTRIBUTION AS DEMONSTRATED BY ISOLATION OF VIRUS IN NATtJRE ....................................... ARBOVIRUSES NOT YET RELATED TO HUMAN DISEASE IN THE WESTERN PACIFIC REGION

8.

29/30 31 37

ANNEX 2 ANNEX 3 TABLE 1

39/40

TABLE. 2

41/42

TABLE 3

(WHO). .......................................... IDENTIFICATION OF ARBOVIRUSES KNOWN TO OCCUR AND CAPABLE OF CAUSING HUMAN DISEASE IN SOUTH-EAST ASIA AND WESTERN PACIFIC REGION •••••••••••.•••••.••••••••.••••• REPORTED CASES OF JAPANESE ENCEPHALITIS IN WESTERN PACIFIC REGION. 1962-1968 •••••••••• MAP NO.1 DISTRIBUTION OF ARBOVIRUSES IN THE WESTERN PACIFIC AND SOUTH-EAST ASIA ACCORDING TO THE REPORTED CASES 1962-1969 ••••••••••••••••••••••••.•••..•••••••

43

47

. r

55/56

•

57/58

.. 1. INTROIXJC'lION The Second Regional Seminar on Virus Diseases: Mosquito-borne Virus Diseases (Arboviruses) organized by the WHO Regional Office for the Western Pacific was held in the WHO Conference Hall, Manila, from 6 to 11 October 1969. Seventeen participants :from fourteen countries attended. The list of consultants, participants, observers and members of the WHO Secretariat is given in Annex 2. The agenda for the seminar is given in Annex :5. The participants elected Dr R.L. Doherty, Chairman; Dr Sujarti Jatanasen, ViceChairman and Dr Lim Teong Wah, General Rapporteur.

Dr Francisco J. Dy, Regional Director, opened the seminar by stating

the

~

main objectives: To review the nature and extent of the arbovirus problem particularly dengue, dengue haemorrhagic fever and Japanese encephalitis in the Region; To review recent developments in the epidemiology, diagnosis and treatment of arbovirus diseases; To discuss control measures undertaken and global surveillance of mosquito-borne virus diseases; and To consider the vectors, their bionomics and their control.

'.

(a)

(b) (c) (d)

The three major topics for the seminar were: Japanese encephalitis, the dengue complex and other arboviruses. Each topic was introduced in plenary session by a working paper of the consultant for the particular subject.

2.

JAPANESE ENCEPHALITIS

2.1 History and geographical distribution of Japanese encephalitis

The known geographical distribution of Japanese encephalitis in epidemic form has been limited to the temperate zones of the Western Pacific Region. However, an epidemic was recently reported in Chiang Mai province of Thailand and this is still under study. Infection with the virus in tropical countries of the Region appears to be widespread with only occasional cases of encephalitis reported. (a) Japan - Since obligatory notification of Japanese encephalitis began in :1964, cases have. been reported yearly throughout the country with the exception of HOkkaido. The incidence has been higher in the southern prefectures. A dramatic reduction in the number of cases was observed in :1968 in Tokyo. For 19 years the morbidity rate was calculated at about 6/100 000 •

. . ..

. - 2 (b) Korea - Epidemics of encephalitis were known in Korea in the past and it appears that Japanese encephalitis has been recognized since 1932. The virus was isolated in 1946. Epidemics occurred at three year intervals with larger ones every nine years. The disease has been recorded for all years since 190,. Japanese encephalitis has been a notifiable disease since 1959. (c) China (Taiwan) - Epidemic encephalitis was first recognized in

..

1935 and has occurred every year since then. It became reportable in 1955 but notification is not compulsory. The virus was first isolated in 1958. from 0.9 to 7.8 per 100 000. (d) Incidence has varied

.

Ryukyu Islands - The disease was at its highest peak in 1963. Morbidity rates were 13.1/100 000 in the past but only 3.34/100 000 in recent years.

..

(e)

Guam - A single epidemic occurred in Guam in 1947. The virus was-apparently introduced, was not reported previously and has not reappeared since. ~ ~

(f)

- One confirmed case in an expatriate soldier was reported in 1962. A serological survey showed antibodies in of the residents surveyed.

40%

(g)

Philippines - Serological evidence of Japanese encephalitis has been repeated demonstrated but no clinical cases have been reported nor has the virus been isolated. MalaySia - Antibodies to Japanese encephalitis are widespread. A few cases are seen in children throughout the year. Many isolations of virus have been made from mosquitoes and a few isolations from man and horse. Singapore - Clinical cases occur yearly and antibody is widespread. Virus isolations have been made from mosquitoes and man. Changing patterns in agriculture and urbanization may make continued maintenance of the disease iJnprobable. Thailand - Isolated cases were recognized in 1965. Serological evidence, supported by recent virus isolations, has confirmed the activity of the virus in Thailand. In 1969, an epidemic was observed in northern Thailand and the virus was isolated from a human case. The study of the reported epidemic is not yet completed. Laos - The existence of the Japanese encephalitis virus has not yet been validated although clinical cases appear to occur.

(h)

(i)

(j)

(k)

..

.. . (l)

- :5 Cambodia - Clinical cases of Japanese encephalitis were reported .in Battambang province in 1969. Serological and virological studies are awaited. Australia and New Guinea - Serological evidence of Japanese encephalitis undoubtedly represents cross-reaction with other group B arboviruses. Ceylon - One isolation from a fatal case was reported in 1969. India - The disease was suspected to occur in 1951.-1952 and was virologicall.y confirmed in an epidemic in 1955. Sporadic cases were found in 1965. Viet-Nam - Three strains of Japanese encephalitis were isolated in Hanoi and one strain in the Republic of Viet-Ham in 1951. Recent cases were found in 1966. Antibodies are common and in 1969, a survey indicated that in Saigon l5% of cl.inical cases of encephalitis are due to Japanese encephalitis virus. Union of Soviet Socialist Republics and Mainland China - An epidemic on the sea coast of the Union of Soviet Socialist Republics was reported in the past. In China, cases appeared among soldiers in Kwantung Peninsula and Manchuria between 1945 and 1946. Ho information is at present available from ma1nl.and China. of Japanese encephalitis

(m)

(n) ( 0)

(p)

(q)

2.2

~idemiology

The incidence of Japanese encephalitis is clearly seasonal. In China (Taiwan), the Ryukyus and south-west Japan, it has a two-month season, usuall.y in July and. August. In Korea as well as in the other parts of Japan, epidemics usually occur in the months of August and September. Generally, epidemics spread northwards. No clear-cut seasonal incidence has been noted for the sporadic cases that occur in south-east Asia where the virus appears to be active throughout the year. The seasonal resumption of epidemics in temperate cl.1mates has not yet been adequately explained, but the onset is definitely rel.ated to temperature and popul.ation of the vector species. The age distribution of Japanese encephalitis in Japan refl.ects the past experience of the popul.ation with Japanese encephal.itis virus infection. The age-specific morbidity pattern has been changing since the late 194o's and is highest now in the age group above 50 years in south-west Japan. Studies indicate that in those areas the incidence of Japanese encephal.itis neutralizing antibody among the older age groups is l.ow. In Korea and China (Taiwan), on the contrary, the disease affects chUdren. The current explanation for this di1'1'erent age pattern relates to the higher incidence of Japanese encephalitis virus infection in Korea and China (Taiwan) in comparison with Japan. Presumably repeated antigenic stimul.i by super-infection keep the immunity level of adul.ts in Korea and China (Taiwan) at a high level.. Available information suggests a gradual decrease in t he rate of inapparent infection during the l.ast ten years in Japan •

.

- 4 There has been a consistent difference between the sexes in morbidity Males develop the disease more often than females, but the case fatality rate in female is higher than male. No explanation has been offered for this observation yet. and case fatality rates.

..

Another factor is the influence of urbanization on Japanese encephalitis epidemics. The recent decrease of Japanese encephalitis epidemics in Tokyo would probab~ be ascribed to urbanization though it cannot be denied that in some cities of Japan intensive vaccination progr8.llllles have influenced the age-specific morbidity patterns to an appreciable degree. 2.3 Clinical manifestations of Japanese encephalitis

The incubation period for human Japanese encephalitis varies wide~ and is estimated to range from four to fourteen days, and more often from a week to ten days. In typical cases, the disease begins abrupt~ with fever, headaches and meningeal irritation. Marked and increasing disturbance of the sensorium is one of the cardinal symptoms during the first 48 hours. Convulsions are cormnon in children. Manifestations of motor neuron disease, usually of the upper neuron type, and of extra-pyramidal tract disease are frequent. The fever is sustained and reaches its peak within four to five days, after which it subsides gradually. Fatal cases us~ progress rapi~ into coma and die within a week to ten days. During the first week of illness, a moderate to appreciable degree of leucocytosis is seen. This grad~ subsides to a normal level. The cerebrospinal fluid almost 1nvariab~ shows a pleocytosis consisting of mononuclear cells ranging between 100 to m/ cmm. The glucose content is either normal or slight~ elevated. Moderate~ raised protein is also cOlDDon. Prognosis varies according to the age of the patient rather than to the geographic endemicity of the disease. The case fatality rate is near~ 50% in patients older than 50 years of age; in children, it is 20% or less. Children aged 1 to 4 years show a remarkab~ high rate of sequelae ranging from 30 to 35%. Complete recovery takes place in 60 to 70% of the patients whose ages are between 5 and 40 years. The sequelae can be motor, mental, psychological or a combination of all three. 2.4 PathogeneSiS of Japanese encephalitis

.

Japanese encephalitis in humans is a result of a virus infection and the response of the human body to the infection. Recent studies in mice inoculated by a peripheral route demonstrate viraemia. After peripheral invasion, the virus is first found in the local lymph nodes. Viraemia can be detected short~, probab~ following involvement of more lymph nodes and bone marrow. In contrast to the extent of findings in experimental animals, man has not been similarly studied in the pre-clinical phase and viraemia has rarely been reported. Thus, the early pathogenesis in man is entirely cOnjectural. Since few of those infected develop disease, it is usually considered that there is an arrest of multiplication of virus, either prior to or after involvement of neural tissues by the body's defense mechanisms. Wi thin the central nervous system, when virus does involve it, there is direct destruction of selected neurons accompanied by an infl..amrlatory reaction with oedema. In some cases, this progresses

•

- 5 to a fatal termination. An element of hyper-sensitivity has been suggested as an explanation for the excessively: high case fatality rate of older persons in Japan, since it appears probable that most of these are not primary infections and antibody levels may have-fallen to levels below those affording protection against viral invasion. In addition to the possible role of an immunologic mechanism in older persons, Dr Hugh Webb has proposed the hypothesis that the damage of arboviral encephalitis is due principally in all age groups to a virus-antibody complex rather than to primary massive neuronal. destruction by virus. Some experimental work appears to support this. 2.5 Laboratory diagnOSiS of Japanese encephalitis

A1though the accuracy of clinical diagnosis can be fairly high in a large epidemic, the specific diagnosis is made only by finding the virus or viral antigens in the brain of patients or by serologic tests. Virus isolation or proof of a fluorescent antibody (FA) positive antigen requires autopsy or post mortem biopsy of fatal cases. The frequency of virus isolation from the brain depends on the da;y of illness. A high positive rate of virus isolation is obtained from brain specimens of those patients dying within the first week of illness. Almost no isolation can be expected later than the tenth day. Virus isolation from cerebrospinal fluid is very rare. The detection of an FA posi tive antigen in the nerve cells of brain specimens is extremely useful during the second week of illness when virus isolation becomes increasingly difficult.

For the patient who. survives for more than two weeks, haemagglutin~ tion-inhibition (HI) tests provide definite answers in nearly 80~ of cases if paired sera are collected in the proper manner and other cross-reacting group B viruses are not being transmitted in the area. Recent studies indicate that the maj or components of' the complement-fixing antibody are found in the IgG fraction which develops after the tenth da;y of illness in primary infections. Sera for the HI test' should be obtained in pairs. The first specimen is collected between the first and fifth day of illness, the second between the fourteenth day and sixth week of illness. I f a patient is suffering critically, an· effort should be made to collect the serum pair wi thin a period of not less than fiVe dSys: and attempt to get one post mortem if death occurs. Sero-diagnostic criteria should be established in each area of ecological unifOrmity carefully considering the i!llllWlity level of the population which reflects the degree of endemiCity and the extent of vaccination programmes. Experience with a new 2-mercaptoethanol.(2-ME) technique to distinguish the IgM fraction of antibody which develops at an in1tial stage of infection is promising but further study in the field is required. At the moment, it may be justifiable to interpret more than a four-fold (~ * eight-fold) titre

*means

equal to or greater than

- 6 decrease of specific IgM g~obu~in, IgM is destroyed by 2-ME and cannot be removed·for testing by this method as indicating a recent infection. The presence of 2-ME resistant antibody in the acute stage serum has ~ttle meaning since encep~tic manifestations fo~owing secondary group B arbovirus infection have been known to y1e~d IgG antibody from the beginning of the 1~ess. In tropica~ areas in the Region, where severu re~ted group B arboviruses are common, the sero~og1cu diagnosis of Japanese encephUitis infection is comp~cated and diffic~t. It may be necessary in same cases to emp~oy neutraLization tests andlor CF tests to determine the specificity of the antibody demonstrated. Even then, it ms::! not be possible to make a clear-cut differentiation, a~though use of the plague reduction neutralization test in appropriate ce~ c~tures may provide specific res~ts. 2.6 Eco~ogy

..

of Japanese encephalitis virus

In contrast to past studies which accUIllUlated a great amount of information and data about Japanese encephalitis during re~tively limited periods of observation, present studies emphasize the eco~ogy of the virus over ~ong periods with the fo~owing principal objectives: (1) (2) iso~ted

.

to determine the combination of factors that inf~uences the degree and time of virus activity, and to determine a formu~ for forecasting epidemic activity.

During the past decade, the Japanese encephalitis virus has been from severa~ species of culicine mosquitoes in Japan, Korea, China (Taiwan), Mala;ysia, Singapore, Thailand and India. The principu vectors involved and their bionomics are discussed briefly in the section below on Vectors and Control (see section 2.8). Culex tritaeniorll.ynchus summorosus is the most widely distributed vector of importance. In the Guam epidemic of 1947, Culex annulirostris marianae was considered to be the vector. ----On the basis ot exper1mentu infection studies, it has been shown that Culex tritaeniorbynchus summorosus is an efficient vector ot Japanese encephalitis virus. Multip~ication of the virus is af:f'ected by ambient temperature as is also the ~ongevity of the mosquito. Virus multiplication does not take place below lOOC. At 28OC, the maximum virus titre in the mosquito is reached after about seven to ten days. It is r0¥.8hly estimated that an infective mosquito will inject about 103 to ~ weanling mouse intracerebru LD50 units of virus when it feeds. In temperate zones, the Japanese encephuitis virus infects vertebrates during the summer season. Virus activity is detected annually in vector mosquitoes first and, subsequently, in the vertebrate amplifying hosts. Good vertebrate amplifiers must have the fo~owing qualifications: (1) be able to maintain a high titred and relatively long lasting viraemiaj

• (2) (~)

- 7have a rapid population turn-over, and be preferred hosts of the mosquito vectors invol.ved.

The first vertebrate .hosts recognized in Japan and Okinawa were certain species of birds and it was established that they have plqed a role, in past epidemics, in the distribution of the virus and as amplifiers of virus activity. In SaDe epidemics, as in Okinawa in l.9lt5, birds appeared to have plqed the major role in the essential. absence of other vertebrate hosts other than man.

At this time, &wiDe are considered the IILOst important amplifier in Japan and China (Taiwan). Limited studies al.so indicate that they are important hosts in Singapore and parts of Mal..aysia. Swinel.ose their maternal. antibody between about three to seven months of age. In Japan, the highest number of non.1!11D1 me susceptibl.e pigs occurs when they reach the age of about seven months. Massive infection with Japanese encephalitis virus then occurs in a very short period of time in a given area. Experimental. viraemia in swane lasts from two to six days, often with the virus titre reaching 1.0 suckling mouse intracerebral. LD 5O/ml.. Antibody devel.ops within seven to ten days. Experience indicates that human outbreaks can occur wi thin two to three weeks after mass acquisition of antibody in the swine popul.ation. Therefore, it is fel.t that periodic assessment of the prevalence of HI antibody in the swine population me,y be a useful. tool. in predicting epidemic actiVity, al.though the time interval. is short •.

•

The compl.ex factors shown in Annex l. il.l.ustrates the transmission cycl.es of Japanese encephalitis virus. Factors that infl.uence transmission and epidemics incl.ude temperature, raintal.l. and other c.l1matol.ogical factors, density of amplifier hosts, sequence of activities related to rice cul.tivation - especially irrigation, density of vector IILOsquitoes - synchronism of the occurrence of viraemic am;pl11'iersand vectors, and the 1mnul De status of the human popul.ation. Despi te several. studies in ~cent .years, no satisfactory explanation of overwintering of the virus in temperate climates has yet been advanced. Recent work, however, has suggested that certain hibernating vertebrates, such as bats, snakes, and lizards, infected in one year, me,y maintain the virus throughout hibernation and become viraemic again after cessaticn of hibernation. Recurrence of viraemia me,y possibl¥ al.so occur occasi~ in pregnant swine. In some tropical. countries of the Region, the virus is active throughout the year with no apparent seasonal. relationship. Al.though swine are cOIIIIIonly infected in those areas (including wil.d boar in Malaysia), the involvement of other vertebrate hosts remains to be determined.

2.7 Vaccination Immediatel¥ atter World. War II, American workers utilized experimental. mouse. brain and chick embryo formalin-killed vaccines which atter being tried in troops were considered inadequately effective, at l.east in adults •

...

- 8 Japanese workers continued those efforts and in 1954 a relatively crude mouse-brain and formalin-killed vaccine was produced, using the N~ama strain, and was employed for the protection of children in Japan. Although no cases of allergic encephalitis were reported in inoculated children, this vaccine, after concentration and combination with Freund's adjuvant, produced allergic encephalom;yeli tis in guinea pigs. Successive efforts were made to purify, reduce the nitrogen content and increase the potency of the vaccine. By 1965, two kinds of partially purified vaccines prepared from infected mouse-brain had been produced in Japan. One is prepared by ethanol-precipitation of the virus suspension, the other by ultracentrifugation of protamine and active carbon-treated virus suspensions. Both have a nitrogen content of less than 0.2 mg!ml. These vaccines are extensively used in Japan at present and although there are no definite figures, it is estimated that more than 20 000 000 persons were vaccinated in 1968 alone. An encephalitis vaccine surveillance programme was organized in 1965 and is actively being carried out at present. No serious complications observed after vaccination have as yet been attributed to the vaccine. Efforts to produce vaccines for human use from cell cultures have been made by several workers in Japan, the United States of America and the Union of Soviet Socialist Republics. Among these, the more extensively studied are a killed virus vaccine developed in Hammon's laboratory in Pittsburgh, United States of America and one virus vaccine developed by Gr~ton and associates in Seattle, United States of America and in the NAMRU No.2 Laboratory in Taipei, Taiwan. Hammon's vaccine was produced from an attenuated strain of virus passed through primary hamster kidney cells and killed by formalin. Three doses of this vaccine have given satisfactory antibody responses in 92% of 41 human adult volunteers. No large field trials have been carried out yet. The vaccine developed by Grayston is produced in hamster embryo kidney diploid cells and has been tested in about lOO children for antibody response with promiSing results. An attenuated mutant (m mute.nt) was obtained from the Mukoi strain of Japanese encephalitis by Inoue in Kyoto. This strain has been passed through a pig-kidney continuous cell line and has been used for the vaccination of pigs as a means of preventing mul1tiplication of virus in those animals in pre-epidemic periods and consequently hopefully protecting the human population. Experiments carried out so far have shown promising results.

..

•

•

Controlled field trials of the mouse-brain killed vaccine used in Japan have never been carried out in that country. A field trial was carried out in China (Taiwan) in 1965 with a mouse-brain protamine ethanol-precipitated vaccine. About 110 000 children in the three to seven year age group received two doses of the vaccine one week apart and another 110 000 children received a placebo. No fatal. cases were reported in the vaccinated group (two inoculations) while five deaths occurred in

- 9 the placebo group. The preventive effect of two inoculations of the vaccine was estimated at about 80%. No significant preventive effect was demonstrated in the children. who received only one inoculation. After one year, the protective rate of two doses had 4ropped to about 60% and after four years it had practically waned. Another field trial has been carried out this year with a more highly purified and concentrated ultracentrifuged vaccine in Korea. Nearly 40 000 children in the six to seven years old group selected at random among those attending the first year school in Cholia Pukdo province were vaccinated with two inoculations of 1 ml of the vaccine two weeks apart. Another 40 000 children of the same age group in the same province were used as controls. Elaborate measures were developed for the clinical diagnosis of the disease occurring in children of the study group in the trial area. Measures were also taken to carry out laboratory diagnosis on all suspected cases in the area. Sero-conversion rates were studied in a proportion of the vaccinated children and over 80% conversion rates were obtained in vaccinated children using the HI test. Results of neutralization tests carried out with the same sera were not available at the time of the writing of this report. It has happened that 1969 has been a year of very low incidence of Japanese encephalitis in all of Korea and especially in Cholla Pukdo province. Only two encephalitis cases have been reported in the study population to the end of September. It is the intention of the Korean authorities to continue the trial in 1970 with the support of WHO. A booster dose will be given to the children vaccinated in 1969 and the study will be repeated in the same area with a random sample of children of the six to seven years old group in 1970. 2.8 Vectors of Japanese encephalitis virus Culex tritaeniorbynchus summorosus is the most important vector of Japanese encephalitis virus. The role of £. gelidus is based on frequent isolations of the virus from that species in South-east Asia. C. annulus has been shown to be of importance in China (Taiwan). Although-the virus has been isolated from several other mosquito species, it is doubtful that the letter are of significance as vectors.

• •

£. tritaeniorhynchus summorosus breeds in ground water collections such as ricefields, pools, ponds, and various crop fields. In the temperate zones, the species is active from May to October with peak activity in July and August, sometimes September. Its sites of hibernation are not known. In the tropiCS, it is active throughout the year with local variations depending on rainfall, temperature and agricultural practices. £. tritaeniorhynchU6 summorosus is highly zoophilic, but feeds on man frequently although to a lesser extent than on other preferred hosts. It feeds throughout the night, more coumonly outdoors than indoors.

•

- 10 -

.

In the dayti.llle,. small. numbers of speci.lllens can be found resting 1n such places, as f1e1ds of grass, parsley, potatoes, beans, and rice. However, many specimens ~ be found resting temporar111 at n1ght in houses and stables before and after feeding.

Q. tritaen10rbynchus SUllll1Or08US bas developed resistance to Dm!, dieldrin, and malathioo in SOllIe areas. Q. gelldus and Q. annulus appear to have similar habits and ecological requirements, as far as is known, although Q. selidus ~ be even more hi~ zoophilic, Attempts to control these vectors, especial.ly £. tritaeniorbynchus, have not been extensive~ applied as yet in most countries because of the extensive breeding areas involved, expense, low priority by governments concerned, and problems of insecticide resistance and environmental contamination by insecticides. Further research required to develop effective control methods include: (1) (2) taxonomic and biologic studies of m1ne whether or not it is a hanogeneous population;

£.

tritaeniorpynchus to deter-

development and evaluation of adulticiding methods and emergency control measures such as ultra-low-volume spra;ying of appropriate insecticides from aircraft and from the ground; biological control studies especial.ly in relation to the use of predators and blue-green algae; development of effective surveillance methods as warning device" for increased virus activity such as use of sentinel anima] populations.

(:~)

(4)

•

Chemical insecticides that are considered effective as emergency measures at this tim include dursban, sUlllithion, and fanthion. Some of tbeae are present~ in use for the control of insect :pests of rice.· Future control progr8llllles m1ght consider integrat10n of agricultural and public . health practices in rice-growing areas for adequate abatement of both mosquito and rice pests. A return to the use ofpar1s-green granules in r1cefields may be advisable.

3.1

Introduction

During the sUDIIIer of 1954, an epidem1c disease was observed in children in Manila, Philippines, characterized by fever and acute haemorrhages and in the more severe cases shock, usual.l¥ terminating fatally. The clinical and epidem1ological characteristics of this outbreak were sufficientl¥ unique for the disease to be named Philippine baemorrbagic fever.

•

- II -

Although in occasional severe epidemics of dengue fever in areas of temperate· climate, a few s1m1lar severe, haemorrhagic and fatal caseS bas been described previous~, there is now no doubt that this occurrence in Manil.a and another unreported cne in Bangkok about the same time presented the first of an important series of a new major epidemic disease of children which bas subsequent~ appeared in most tropical countries of south-east Asia, the PhilippineS and Indonesia. It was recClDlllended that this be called mosquito-borne haemorrhagic fever. Dengue viruses and chik\mgUXlya virus were qui~ associated as aetiologicaJ.agents in a number of subsequent epidemics.

3.2 HiStorY and geographic distribution of the Pengue-cO!!!Plex and ChikunejuI!,ya Philippines - Sporadic cases of haemorrhagic fever attracted the attention of clinicians as ear~ as 1950. It was recognized in epidemic form in Manila in 1954 and in subsequent years in other parts of the Philippines. Epidem1cs occurred in 1956, 196O, 1961, 1964, 1965, the largest in 1966, 1967, 1968 and 1969.

•

MaJ or outbreaks occurred in seven provinces. Dengue virus types 2, 3 and 4 were isolated as ear~ as 1956 • .An epidemic of chikungunya was reported in Negros province in 1967. This was ccnfirmed in the laboratory.

Thailand - '!'he disease was identified with certainty in 1958 in the Bangkok epidemic and continued to be active with biennial,. peaks in 196O, ].962, 1963, 1964, 1965, 1966 and l908. Cases are recognized every year. Outbreaks have occurred in most of the 71 provinces except those bordering ~1a. At first restricted to the urban areas in the Central. Pl.a1n, . 1 t .was later identified also in small towns and villages. The four dengue types and chikungunya have been isolated. Cambodia - Dengue viruses 1, 2 and 4 and ch1kungunya viruses were isolated from patients in l.961 and 1962. Human infection appears to be widespread but haemorrbagic manifestatiCllS have not been reported.

&!e!. -

Clinical. cases resembl:l.ng baemorrhagic fever were reported in

1962 and 1968 but the aetiological. agent is not known. Viet-Ham. - Clinical dengue bas been epidemic in Viet-Nam. since the nineteenth century. Haemorrbagic fever occurred in Saigon in l.96O, 1961, 1962 and virological confirmation was obtained in 1963 in the western provinces. It occurred also in 1964, 1965, 1967 and l908. Four virus types were recovered. The disease, confirmed by dengue virus isol.ation, in North Viet-Nam bas been reported by the ~ press. Mala,ysia - Dengue epidemics were reported in 1902 and l904. Dengue virus type 1 was isolated in an outbreak in Kuala Lumpur in 1954. An outbreak occurred in Penang in 1962-l,964. A few sporadic cases occurred in 1965 and 1966 followed by an increase in several states in 1967-l969

- 12 -

..

with peakS in 1967 and 1969. Severe haemorrhagic cases occurred in 1962 to ~964 and in 1969. Dengue is recognized in urban, sub-urban and rural areas. Dengue types ~, 2, 3 and 4 have been isolated. There is serological evidence of past infection with chikungunya virus, but no virus isolations have been made. Singapore - A mild epidemic associated with haemorrhagic symptomatology occurred in 1960. After 1962, incidence and severity increased and cases occurred in 1963, 1964 and 1966. No cases were reported in the last few years. Four dengue virus types were isolated. Sero~ogical evidence of past infection with chikungunya virus haS been demonstrated. Burma - An epidemic of dengue-like disease with marked arthralgia occurred in Rangoon ~ate in 1963. Fragmentary serological evidence supports the clinical and epidemiological diagnosis of chikungunya virus infection. Recent~, disease with haemorrhagic manifestations have been reported. India - Classical dengue has been endemic in parts of India for many years. Virus type 1 was isolated in 1945 and numerous isohtions of types 1, 2 and 4 were made in Vellore between 1960 and 1963 and type 3 in 1968. An epidemic of haemorrhagic disease appeared in 1963 in Calcutta. Dengue type 2 and chilrungunya were isohted. Dengue-like Ulness due to chikungunya and several dengue virus types has been widespread in many parts of India and a s~ percentage developed haemorrhagic manifestations.

•

Ceylon - Chikungunya infection, demonstrated serologic~, was seen in 1964and chikungunya virus was isolated in 1965. Recent~, dengue cases with positive group B serology have been seen and one isolation of a virus tentative~ identified as dengue type 1 has been made. Two fatal cases of haemorrhagic fever, diagnosed clinical~, were reported in 1966. Australia - There has been a long history of epidemic dengue occurring at ten to fifthteen-year interv~, the most recent in 1954-1955. No evidence of dengue infection has been found since then. New Guinea - Dengue was active during World War II when dengue virus types 1 and 2 were isolated. No cases have been reported since then although there is serological evidence suggesting more recent activity of dengue types 3 and 4. Fi.'i - Dengue was epidemic last in 1944-1945. More recent serological surveys have only demonstrated past group B activit.y. French Polynesia - An epidemic occurred in 1943-1944 that was associated with dengue type 1 by subsequent serological studies. In 1964, a clinic~ mild epidemic occurred that ms:y have been associated with dengue type 3 on the basis of a virus isolate that is still under study. Mild haemorrhagic manifestations were reportedly noted in some cases. In 1969, an outbreak has occurred and 1 t is being investigated.

•

•

- 13 China (Taiwan) - No concluSive information is available about dengue infections. Indonesia., Serological studies from. 1964 to 1966 have definitely suggested the presence of antibody in the human population for dengue and possible chikungunya. Clinical haemorrhagic fever has been reported in 1968 and 1969 with laboratory confirmation of dengue infection. Japan - Large epidemics of dengue occurred during World War II in Nagasaki and Kobe (1942-1944) with the isolation of dengue type 1 virus. No cases have been reported since then. Korea - There is no evidence of dengue-like illness or dengue haemorrhagic fever. Western Samoa - There is no information that dengue or dengue haemorrhagic fever has occurred.

3.3 Clinical manifestations It has been exceedingly difficult to describe accurately the clinical manifestations of the haemorrhagic disease syndrome and to differentiate it from those of classical dengue fever and there is considerable lack of agreement on any definition of this haemorrhagic fever. At the WHO Seminar on Mosquito-Borne Haemorrhagic Fevers in the South-East Asia and Western Pacific Regions, held in Bangkok, 19 to 26 October 1964, it was recommended that an attempt be made to have the complex of diseases involved recorded and reported in a systematic manner and diagnostic criteria were proposed. ThiS, with minor modification is again rec~ mended, though it is realized that in our present state of knowledge, "gray" areas still exist. It must also be recognized that dengue-like disease can be caused by many different viruses, not all of them even arboviruses and that aetiology can be established only by a laboratory with adequate capabilities. Therefore, all diagnoses are stated first as clinical and next with aetiOlogy when known. It must also be understood that classical dengue fever as caused by dengue viruses is a disease recognized almost entirely in older children and adults. In children, infection usually results in a mild, undifferentiated fever, not diagnosed clinically as dengue, and not of a degree of severity to warrant medical attention, much less hospitalization. On the other hand, haemorrhagic fever, with or without shock, has occurred in most areas as a disease principally of infants and young children, is frequently of frightening severity and if medical care and hospitalization are available, patients seek such attention. There exists gradation between these extremes which presently cannot be sharply defined and will be called by one physician dengue fever and by another dengue haemorrhagic fever. It is hoped that the follOWing descriptions and recommendations will assist in standardizing diagnosis and make reporting more meaningf'ul. and consistent: (1) Undifferentiated fever - This is a very mild febrile illness of short duration usually occurring in smal.l children frequently considered to be of respiratory origin, without most of the characteristics of the syndromes described below.

'.

- 14 (2) Dengue fever syndrome - This occurs most frequently in older children or adults and is usually characterized by fever and severe myalgia and/or arthralgia and leucopenia, with or without rash or lymphadenopathy, but including many of the fOllowing: biphasic fever pattern, severe headache, pain on moving the eyes, positive tourniquet test*, altered taste, mild throm'bocytopenia, a few spontaneous petechiae, or other mild evidences of capillary fragili ty • Haemorrhagic fever** - This is most :frequently a disease of children, manifested by fever, usually without prominent myalgia or arthralgia, usually becoming more severe after the first two d~, positive tourniquet test, rash present or absent, leucopenia usually absent but with several or all of the fo~owing: extensive spontaneous petechiae, purpura, ecchymoses, epistaxis, hs.ematamesis, ma.l.aena, marked thrombocytopenia (~100 OOO/Cl'lI'A), prolonged bleeding time (> 5 min.) or elevated pro-thrombin time, hypoproteinemia t 5.5~), increased hs.ematocrit, and maturation arrest of megakaryocytes. This is further sub-divided into: (a) (b) Without shock With shock. The pulse pressure is 20 111m of Kg or less with collapse of the patient. Shock may occur without the conspicuous haemorrhagic manifestations, but with most of the other serious disturbances of the haemostatic mechanism described above as essential criteria.

( ;)

For all of the above categories, the aetiology ,should be stated when known, or stated as unknown.

;.4 El!idem101ogy and aetiOlogy of dengue haemorrhagic fever Dengue viruses of types 1, 2, ; and 4. have been isolated from the blood of many of the patients with haemorrhagic fever and from Aedes aemti princ1p~, occasion~ also from Aedes albopictus. The seasonal distribution, the geographical association of cases with!. aemti. the association of classical dengue occurring at the same time in dengue susceptible older children and adults, and other similarities between the

*The tourniquet test should be employed in a standardized manner (e.g., Rumpell-Leede1s test). This should be done with a blood pressure cuff and not with a tourniquet. **To be considered in differential diagnosis are: thrombocytopenic purpura, haemoph1l1a of genetic origin, meningococcemia, scarlet fever, haemorrhagic lEasles, rubella, enterovirus infections with rash, rickettsial fevers such as scrub typhus, leptospirosis, etc. ~

Means equal to or less than.

,. Means greater than.

- 15 known epidemiology of dengue fever and this new severe epidemic disease

syndrome, have conclusivel¥ shown that this new syndrome is caused princi~ by dengue viruses and transmitted principalJ\y by ~. aegypti. What additional factor or factors have contributed to the observed change from a disease previousl¥ so benign in children to one so severe, presents a challenge to virologists and epidemiologists. During the first large epidemic in Bangkok in 1958, chiltungunya virus was isolated for the first time outside of Africa. It produced a denguelike disease during the same period of time that dengue infections were occurring and many children were infected more or less s1mu1taneousl¥ wi th both viruses. This led investigators to consider the possible role of this virus in the haemorrhB8ic disease syndrome. It was soon established that it had not been active in Manila in 1956 in the haemorrhagic fever epidemic but was subsequentl¥ found present together with dengue in many other outbreaks of dengue-like diseases or of haemorrhagic fever and incriminated as causing severe fatal disease in Calcutta in 1963. The principal unsolved problem in aetiology and epidemiology involves the factor or factors which have led to this marked change in the disease and its age group, produced by dengue viruses. Changes in virulence of certain of the viruses have been and still must be considered as one factor but this is not direct4r associated with any one serotype. More or len simultaneous infections with two viruses, both dengues, or dengue and another not yet isolated, have been suggested as hypotheses. A host factor, rather than an environmental one, is current4r receiving favourable attention. This is not believed to be genetic or nutritional, but immunological.

,

One consistent finding in addition to others already stated tends to support hypotheses involving either double dengue virus infections or sequential ones (immunologic sensitization), either by two different serotypes. In every epidemic area of the severe haemorrhagic disease syndrome where adequate studies have been carried out, several, and frequentl¥ all four recognized maJor serotypes of dengue viruses have been found. Greatl¥ increased and more rapid travel since World War n has probabl¥ led to the introduction of additional virus types where onl¥ one or two previousl¥ perSisted in an endemic status. This leads to more frequent double or sequential infections by t,ypes with which the persons, mostl¥ children, were not previous4r infected. Vertebrate hosts for dengue, other than primates, probabl¥ do not exist. Monkeys and forest mosquitoes have been suspected as a jungle reservoir, as in yellow fever. Recentl¥, an isolation has been made from a sentinel forest monkey and probable isolates have been made fran A. albopictus in the same and other forest areas. Many monkeys in some tropiCiir' areas have dengue antibodies. The importance of these findings is yet to be evaluated. Chikungunya virus may have other vertebrate hosts and does have a wider spectrum of vectors than dengue but current information presents difficulties in interpretation of reservoir hosts and no firm conclusions can be drawn.

- 16 -

•

3.5 Pathogenesis of dengue haemorrhagic fever Not all aspects of the pathogenesis of dengue haemorrhagic fever have been adequately elicited, but s~ are reasonably well established, at least for the more severe syndrome leading to shock. Several hypotheses to explain the change in the character and severity of dengue infection have been presented above. One hypotheSiS which has gained considerable support suggests that the severe disease is basically an immunologic one. Capillary damage leading to extreme permeability is predicted as occurring when a large amount of virus is complexed with an unusually large amount of antibody. This is most likely to occur in a person sensitized to some common antigen that the current dengue serotype shares with a previous heterotypic infecting virus, usually considered to be another type of dengue. The disease also occurs in some patients with a primary antibody response as in infants below one year of age. The proponents of the immunological hypothesis consider such cases due to sensitization by maternal antibody. They also suggest from various data that sensitizing (primary) and eliciting (secondary) dengue infections must occur within a period between three months and five years to result in severe aberrant (haemorrhagic shock) dengue disease.

3.6 Pathology of dengue haemorrhagic fever The combined picture of haemorrhages, hepatomegaly, depression of bone marrow, and proliferation of the reticu1o-endothelial system is quite distinct. Gross necropsy findings observed in 100 cases of clinically-diagnosed haemorrhagic fever in the Philippines are presented in Table 1.

3.7 Laboratory diagnosis of dengue infections Numerous advances in knowledge on laboratory diagnostic methods have been made since the last WHO regional seminar involving dengue infections. Not all of these have been fully exploited, but it is readily apparent that means are now available to diagnose successfully and specifically by type, a higher proportion of dengue infections than ever before. The most specific diagnostic method is virus isolation. Fortunately, dengue viruses are among those arboviruses which can very frequently be isolated from a living patient. The virus is present in high titre in the blood during the first several days of fever. Following isolation, identification must be carried out with suitable typing sera, best prepared by a four to six months bleeding following a single injection of a monkey proven to be free from any previous group B arbovirus infection. Isolation and identification require either a relatively virus-free colony of susceptible mice or cell cultures, the latter usually of a continuous monkey derived line or one from mosquito cells. Marked advances in technique for use of cell lines have recently occurred, usually involving plaquing techniques. They have proved to be time saving, sensitive and highly quantitative.

•

•

- 17 Serological diagnostic tests with paired specimens can be performed, by the methods of ha.emagglutination-inhibi tion (HI), complement-:t'1xation

(CF) or neutralization (N). All require special reagents and the N test requires suckling mice or suitable cell cultures. All'require well-trained, experienced technicians. Interpretation of results (significant and highest rise in antibody ti tre betweel\ the two specimens to one of the four dengue virus types) is quite readily interpreted in primary type dengue virus infections, but . unfortunately, in endemic, tropical areas where haemorrhagic fever occUrs, few infections are of this primary type. Most patients respond in an anamnestic manner and determination of the infecting type and even of Which group B virus has infected becomes very difficult. Often, the' only interpretation possible is that a group B infection bas or has not occurred. In developing countries, the universities and health departments find great difficulty in supporting these essential diagnostic facilities and presently what is available has been largely through the assistance of . outs1de agencies. However, it is recommended that ministries of health place higher priorities on virus diagnostic laboratories for highly important virus diseases such as these. Epidemiologists cannot car'/:'Y out their tasks and devise suitable control. measures without prompt, speci:t'1c, laboratory aetiological diagnoses, Cell cultures are becoming increasingly important in many areas of research and the establishment of facilities for such and the training of technicians are strongly recommended. Where currency exchange and customs difficulties interfere with obtaining necessary supplies, attention at the highest pol.1tical level should be directed to the need for the rapid sol.ution of the problem. Importation of safe, non-infectious antigens for serol.ogical tests (HI or CF) Sh()Ul.d be arranged so that live agents for diseases not known to be present in tl:ie"~ountry need not ~imported. Such reagents for dengue viruses have now become available. In summary, the· accurate and specific laboratory diagnosis of dengue virus infections in a tropical &tea, where they most frequently occur, bas greatly improved potential but with increased sophistication, not through simplification of procedures. No single, simple; standardized method of virus isolation, identification or serological test has been developed. Instead, an increasing number of rel.atively complex types of procedures have become available which, in the hands of experienced virologists, are capable of offering much more rapid and specific results than was previously the case. The most specific and satisfactory method is that of virus isolation and identification, possible in a high proportion of cases seen reasonably early in the illness. Serology has improved to the point that significant antibody changes to a group B virus can be detected with greater frequency and certainty by using a combination of several tests. However, speci:t'1c virus type diagnosis among closely related group B viruses is still difficult and frequently unattainable.

- 18 -

•

3.8 vectors of the dengue viruses Reference is made to the report of the WHO Seminar on Mosquito-borne Haemorrhagic Fever in the South-East Asia and Western Pacific Regions (Bangkok, 1964) in which brief but appropriate remarks on !. aemti contro~ were made that are sti~~ applicable.

The dengue vectors of importance include Aedes aegypti, !. albopictus, A. pol.ynesiensis, and probabl¥ members of the !. scutellaris complex. There are several other species of the subgenus Steaosria that may possibl¥ p~ a role in the transmission of the dengue viruses in some loc~ities. It is important to note that !. ~bopictus has not been found to play any significant role in epidemics of haemorrhagic fever and probabl¥ will not under most circumstances. It is important to recognize the different ecological requirements and habits 0:£ the two dengue virus vectors, !. aegypti and ~. a~bopictus, in relation to the application of effective control measures. Control directed against !. aegypti will not be as effective against !. ~bopictus or the other Stegomyia species in the areas involved. aegypti is in Asia an introduced domiciliary mosquito onl¥ found intimatel¥ associated with households and man-made breeding places, with few exceptions, and is principally found inside homes as an adult.

!!.

!. albopietus, however, will breed extensivel¥ in natural water containers as well as man-made containers and is found in forest areas, rur~ areas, and urban areas. The adult is more cOllll1only found outdoors than indoors. The numbers of !!. albopictus are normally greater awa:y from the crowded central parts of cities in contrast to ~. aegypti, which usually diminishes in numbers awa:y from human concentrations. It is, therefore, clear that the control of !.. albopictus is more complicated and difficult to approach than for !!. aegypti, but fortunately appears to be much less needed. Effective control on a wide scale of !. albgpictus requires further research and development of new methods, which might include: (a) (b) biologic~ measures, and

improved method of application of chemical insecticides that will reach the often secretive and inaccessible breeding places.

Effective control for !. aegypti must emphasize adequate public health education, environmental sanitation and, where necessary, the application ot legal measures. With improved economies, an adequate supply ot piped potable water would automatically result in reduction of the !.. aegypti population, while an increase in waste products such as metal and plastic food packages, automobile parts, and tyres would result in an increase in breeding p:la.ces.

- 19 -

Surveillance of ~. aegypti by the "single larva per container" method is useful in establishing measurements for evaluation of the vector population and control. Successful and recommended chemical control methods include: (a) (b) abate as 1% sand granules as a larvicide, and malathion as an adulticide applied by fogging and/or ultra-lowvolume aerial. spr~ing. Adulticiding is considered the method of choice during an epidemic. Aerial application is recommended on4' as an emergency' measure because of its high cost.

A combined programme of larv1ciding and adulticiding has obvious advantages over the use of a single method. While larviciding is most important in a long-term programme, adulticiding, in itself, is a temporaxy measure. The optimal. quantity of insecticide to be used in ultra-law-volume aerial spraying must be determined by further research to avoid "overkill". The frequency and timing of application of adulticides must be determined especially in relation to econo~ of an emergency operation intended to interrupt virus transmission.

,

The availability of abate and malathion and effective measures of app4'ing them allow an optimistic approach for the effective control of ~. aegypti. Both have a relative4' low toxicity for vertebrates and are comparative4' bio-degradable. Proper application can reduce a vector population to 11> in a short period of time and it is hopeful4' predicted that the usefulness of these chemicals will persist for many years. Dursban is recommended as a very effective insecticide for application to breeding sites such as tyres and junk piles that are particl1lar4' difficult to control and do not involve water used for human or animal consUllij)tion.

3.9 Prospects of vaccine for the dengue viruses As in other arthropod-borne diseases, control, whenever pOSSible, is preferab4' achieved through vector control - a change in the environment that benefits all persons - not through repeated vaccination of individuals. Aedes aegypti control is possible, though cost4', but is probab4' far less cost4' than community-wide vaccination in the long term. Regardless of these general4' well-known principles, the control of the dengue virus complex of diseases by vaccines has been serious4' considered and presents many difficulties not encountered in several other arbovirus diseases. Attempts to immunize man with dengue viruses that have been inactivated in the manner appropriate for other arboviruses have failed as was the case for yellaw fever virus. There are four quite distinct antigenic types of dengue virus, and probab4' many varied sub-types or variants within these. It may and probab4' will require several vaccines, not one, to protect persons in the endemic areas where haemorrhag1c fever occurs. Since the only method now recognized as possibly effective is by using live, attenuated

- 20 virus strains, there appears to be a distinct possibility that if the fatal or severe disease is an illJll.UIlol.ogic one, the 1ntectionproduced by the vaccine might el.icit a dangerous response, or might produce the sensitization foll.owing which the next natural. infection woul.d produce haemorrhagic fever, which the vaccine is supposed to prevent. For these and many other reasons, research on dengue vaccines is not receiving ereat attention, nor do most scientists anticipate earl.y or great success. However, some research is in progress in several. l.aboratories. An improved type 1 attenuated mouse brain vaccine free fran recognized l.atent mouse viruses is being prepared and may soon be used in a fiel.d trial., but chance will very l.1kel.y dictate i;hat it will be empl.oyed against a heterotypic dengue virus. A previous trial. of a cruder preparation showed onl.y modest protection under such circumstances. Other l.aboratories are working with non-infectious fractions of dengue viruses, probabl.y l.ess dangerous than l.ive virus, but this work is in too earl.y a stage to prognosticate regarding success. If' successful, the vaccine ( s) will probabl.y be quite expensive. In concl.usion, it appears that dengue virus diseases are more susceptibl.e to control. by attaCking the vectors than by use of vaccines. Use of vaccines when avail.abl.e wil.l. probabl.y be for special. popul.ation groups under quite unusual. circumstances, and may not be suitabl.e for mass use in hyperendemic areas where needed most.

3.1.0 Therapy Unf'ortunatel.y, as for practical.l.y all other virus diseases, there is no specific therapeutic agent yet recognized which can directl.y a:f'fect the replication of the aetiol.ogical. agent. All therapy must therefore be supportive and directed at correcting the pbysiol.ogical. disturbances, signs and symptoms. Fortunatel.y something can be done to prevent or el.l.eviate the shock syndrome if done in time. However, this requires considerabl.e clinical. skill and l.aboratory asSistance. When indicated by suitable te.sts, prior to shock, the electrol.yte bal.ance shoul.d be caretul.l.y maintained, the great l.os's of "protein from the vascul.ar system compensated for and the red cel.l.s and bl.ood vol.ume maintained at suitable l.evels." This must be done with care" since overcompensation can l.ead to equal.l.y severe difticul.ties. OJlYgen also shoul.d be administered. Corticosteroids have not proved signlficantl.y effective.

•

4.

OTHER ARBOVnroSES

4.l. Murray Val.l.ey encephalitis Murr~-Darling basin of Victoria and New South Wal.es, on six occasions

Epidemic encephalitis has occurred in Australla, especial.l.y in the

Since l.9l.7. The causative virus was isol.ated in 1951. and found to be a group Bagent rel.ated to but recognizabl.y distinct from Japanese encephal.i tis virus. Investigations fol.lowing the 1951 epidemic l.ed to the

•

- 21 -

suggestion that the virus did not survive in southern Australia between epidemics but was re-introduced from enzootic areas, possibly involving bird-mosquito cycles in northern Australia or New Guinea. Some support for this hypothesis was provided by isolation of the virus from. man in New Guinea in 1956, and from mosquitoes in Queensland in 1960 and 1961. Since the WHO Seminar in 1962, only one case of !~ray Valley encephalitis has been diagnosedj the patient died in May 1969, soon after spending a period in northern West Australia and the Northern Terri tory; the virus was isolated from the brain. A study area in north Queensland, chosen because of high immunity rates to Ivmrray Valley encephalltis in children and the IIIC8quito isolations mentioned above, has been studied in some detail. Serological evidence of infection with Murray Valley encephalitis was found there during most wet seasons (January-April) but not at other times of the year. Virus isolation attempts on mosquitoes from. several areas of Australla and New Guinea have not yielded the virus in this period. Further studies are planned, but the possibility that the virus may survive, not in enzootic foci but in shifting infection cycles over large areas of northern Australia may make it d1ff'1cul.t to establish its basic epidemiology. It has not been of publlc health importance in recent years, but remains of potential significance in the future development of northern Australia. Its full significance in New Guinea is not yet known and needs further study. 4.2 Epidemic polyarthritis OutbreakS of mild febrile illness with polyarthralgia and sometimes a papul.ar rash have occurred in Australia on several occasions, most notably in 1956 when several thousand cases were recognized in southern Australia. Study of that epidemic suggested that the causative agent was a group A agent of the Semliki forest sub-group. More recently, Australian workers isolated the Ross River virus and showed it to detect antibody in patients more efficiently and to higher titre than did other members of the sub-group. The virus has not been isolated from patients but is viewed as likely to prove the cause of the disease. The Ross River virus was used for serological diagnostiC tests which have detected small epidemics and sporadic cases at several centres in eaStern Australia each sUllllller and autumn (January-May) since 1962. Virus antibody and isolation studies suggest that mammals, especially kangaroos and wallabies, may be important vertebrate hosts. The Ross River virus has been isolated infrequently from mosquitoes, and what species act as vectors are still in doubt. The disease occasionally leads to joint pain or effusion lasting several months, with eventual recovery, but most cases recover wi thin two weeks. Its differential diagnosiS from other causes of polyarthritiS makes it of some importance. As practitioners become more aware, the disease may prove to be quite common in Australia.

• •

4.3

Sindbis

Sindbis virus, originally reported in Egypt, has been isolated from several species of IIIC8quitoes in Australia, Malq'sia, and the Philippines. It has also been reported from Africa and India. Antibody for Sindbis virus has been demonstrated in the Region in man as well as in other vertebrates, especially domestic animals.

- 22 Although the virus has been associated with febrile illness in man in the past in other parts of the world, only one human case has been detected in the Region. It occurred recently in Australia. Little is known of the ecology of the virus in the Region. Thevirus has been isolated from Culex annulirostris, Aedes normanensis, Aedes vigilax and Mansonia semptempunctata in Australia, C~1C bitaeniorhynchm!. in the Philippines, and Culex tritaeniorhmchus and Culex sinensis in Malaysia. The importance of these species as vectors, however, is not known. 4.4 Arboviruses not yet related to human disease Over 200 viruses are registered in the first published edition of the "Catalogue of Arthropod-Borne Viruses of the World", but if the new arboviruses reported since then and those that research laboratories have not officially reported yet, are added, the total number would be well over 300. While many of these have been isolated from tissues of man and have been associated with disease in man, the majority have been isolated from other sources in nature, such as mosquitoes, ticks and various vertebrate hosts. Many of the latter may produce infection in man as demonstrated by the presence of neutralizing antibodies in normal human sera, but they have not yet been associated with disease in man and very little is known of their ecology. In addition to those reported, several probable new arboviruses have been isolated by research laboratories in the Region, but have not been completely characterized or reported.

It is likely that several other arboviruses reported from neighbouring countries may also occur in the Region. The recent isolations of Zika virus in Malaysia and of Wesselsbron virus in Thailand, as well as chikungunya virus reported previously, suggest that other such African viruses may also occur in this area. In addition, the widespread geographical distribution of a virus such as Sindbis (which has been isolated in Africa, India, Ma1a¥sia, the Philippines and Australia) must lead one to consider the possibility that other arboviruses, known only in distant areas, may be found here also.

Serological surveys have indeed indicated that other arboviruses have been active in the Region, but such evidence may not be considered conclusive until the viruses have been isolated from local sources. Table 2 presents the ]alown geographical distribution of arboviruses not yet related to human disease in the Western Pacific Region. Table 3 presents the sources from which viruses have been isolated in nature, those for which neutralizing antibody has been demonstrated in man, and those that cause disease in man in other parts of the world.

- 23 Although the Eastern Equine Encephalitis virus bas been included it 1s probable that the reported isolations in the Philippines and Thai~d were not valid. Encephali tis has been produced in human volunteers experimentally by Langat virus, which is very closely related to RusSi~ Spring-Summer' Encephalitis and Kyasanur Forest Disease, both severe infections in man. Both Wesselsbron and West Nile viruses cause illness in man in other parts of the world. Although Zika virus has not been unequivocally associated with buman illness in nature, one case of a febrile illness was attributed to it probably as a result of a laboratory infection in Africa. The majority of the agents listed bave been isolated fram mosquitoes, including several species that feed cOllll1only on man. Although the majority of these agents probably involve vertebrates other than man in their natural ~cles, man may became significantly involved when the vectors are anthropophilic. An outstanding example would be Zika virus, which bas been isolated from Aedes aegy;pti, a bigbJ.;y anthropophiliC species. Recent stUdies in Ma~sia of approximately 2000 febrile illnesses sbowed no unequivocal evidence that any case had been caused by any of tbe known arboviruses other than dengue and Japanese encephalitis. The majority of the specimens studied, however, were received from hospitals. It was therefore suggested that if illness is being produced in man by other arboviruses 1n Mals.ysia, that 1 t is very mild and not reacbiDg the hospitals. Attempts to associate disease with those viruses would then require study of mild non-bospitalized fevers. In c.onclusion, the actual or potential importance of these arboviruses in human disease can not be clearly establisbed at this tir:Je. It is l1keJ.;y that those that are transmitted by anthropophilic vectors may br responsible for mild illnesses. It must also be considered that, in future, changes in environmental condi tiona (such as increased urbanization, clearing of forests, new agricultural practices, and development of new towns and villages) and changes in host susceptibility may result in some of these viruses assuming great importance. 5. VECTORS AN)

•

,

THEm CONTROL

The important known mosquito vectors in the Western Pacific Region include Culex tritaeniorhyncbus, £. gelidus, and £. annulus for Japanese encephalitis virus; Aedes aegypti, ~. albopictus, and probab4r members of the Aedes scutellaris complex for tbe dengue viruses, !. aegypti and possib4r !. albopictus for cbikungunya virus and Culex annulirostris for Murr~ Valley encephalitis virus.

- 24 -

Effective control programmes for these vectors would best be based on a combination of methods supported by concommitant surveillance, research, frequent re-evaluation, and a thorough understanding of the ecology of the vector. Methods and approaches to control to be conSidered in planning a programme includel (1)

mechanical measures j chemical measures j physical measures; biological measures; environmental manipulation; genetic measures; behavioural determinants; legal measures, and public health education.

(2) ( 3)

( 4)

(5) (6)

( 7) (8) (9)

A comprehensive understanding of vector ecology and the dynamics of vector populations in each area is essential. Development of practical and economical methods to apply a new approach, life-table analysis, to mosquito populations would yield precise quantitative information for more effective surveillance control programmes. Important vector ecological factors to be considered include feeding habits, dispersal, and micro-environments of larval and adult stages. Adequately staffed surveillance teams will determine the extent of the problem and methods, materials, equipment, and personnel to be employed. A well-qualified research unit is important to the control programme for evaluation of effectiveness of surveillance, development of improved methods of surveillance, and assessment of new control methods and materials. £>.

•

INTERNATIONAL CO-OPERATION AND WHO ASSISTANCE

The recent emergence of arbovirus disease as an important public health problem in Eastern Asia has prompted the countries concerned to request Western Pacific Regional Office and South-East Asia Regional Office for assistance in the development of co-operative programmes in this field. After the initial WHO seminars hel.d in Tokyo in 1962 and in Bangkok in 1964, the present seminar convened in Manila in 1969 was able to review the following progress in the study and control of Japanese encephalitis, dengue haemorrhagic fever and other mosquito-borne virus diseases.

• Japanese encephalitis (JE)

- 25 -

As a first step, WHO consultants 'Were sent to Korea and China ('rai'Wan) to promote epidemiological. and virological. studies of this disease. Recently, WHO sent a group of international. experts to Korea to advise the public health authorities on the organization and execution of a controlled field trial. with the best JE vaccine available, and the trial. was performed this year. Following the visits from a staff member of Western Pacific Regional. Office, a unit to study the ecology and control of the. vector mosquito, known as the Japanese Encephalitis Vector Research Unit (JEVRU) 'Was established in the National Institute of Heal.th .at Seoul in 1969. An additional. JEVRU unit is being established in Taipei, Taiwan. Dengue haemorrhagic fever (DHF)

•

After the meeting in Bangkok, two conSUltants 'Were sent to those countries in South-East Asia in 'Which DHF was known or suspected in order to eval.uate the dimensions of the problem. As a result, a programme of international. sUl;'Veillance was developed, which has been c2I'ried a considerable distance by the co-operating countries. After a conference had been held in Geneva on1he epidemiology and control of Aedes aegypti in 1964, the Aedes Research Unit (ARU) 'Was established in the following year in co-operation with the Thailand Ministry of Heal.th at Bangkok. The work of this unit has quantitated the bionomics of the vector and has developed certain insecticidal control measures which are highly effective and relatively inexpensive. Other arbovirus diseases WHO inaugurated in 1960 a general programme on arboviruses based on a network of International. and Regional. Reference Centres. This programme has provided assistance to countries in various parts of the world on the identification and characterization of the arboviruses present in their areas. It has also given assistance in the training of national personnel in laboratory and field techniques of arbovirus investigation. Largely through its six epidemiological. research units in the field, WHO is collecting and storing in the computer information on the actual and potential mosquito vectors of arboviruses as a contribution to world-wide surveillance • WHO has provided consultants to some countries in Western facif1c Regional Office and South-East Asia Regional. Office in virology, for the introduction of new laboratory procedures, and in entomology, for training of entomological staff in Aedes surveillance. Otber organizations Other organizations, based on co-operative endeavours among some of the countries in the Region, have recently encouraged and initiated cooperative efforts in public health research and training that include arbovirus problems. These include South-East Asia Ministers of Education Secretariat, and the Thai-Malaysia Public Health and Malaria Border Co~e­ rence.

• •

t

- 26 -

7.

SURVEILLANCE

The "Technical Guide for Surveillance Programmes for Dengue Haemorrbagic Pever" (ESQ 69.3) was discussed by the seminar and the following points made: (1) It is important to establish adequate surveillance at national and international levels in order to provide for ear13 detection of outbreaks, application of control measures, and to monitor factors involved. Cases of DHP should be reported through appropriate local and national authorities to the EpideMiological Surveillance and Quarantine Unit at WHO, Geneva, USing a standard report form. Recognition and classification of cases by aetiology and degree of clinical manifestation are essential. Recommended criteria for such a claSSification are set forth above in the section on Clinical Manifestations of Dengue and Dengue Haemorrhagic Fever. It was emphasized that the demonstration of a secondary antibody response should not be included in the criteria for the differentiation of thesyndromes presented, but should be considered ~ in the subsequent interpretation of laboratory results used in defining the aetiology. Entomological surveillance for determining distribution, denSity, and activity of Aedes aegypti and !. albopictus in each country is urged and may be accomplished by the use of the following recommended quantitative measures: (a) (b) Single - larva collection method (shows distribution). Human biting index (shows number of mosquitoes attracted to man dependant on time of day, length of period, number and attractiveness of COllectors). Aedes aegypti index (per cent. of positive houses of total number examined). Container index (per cent. of positive containers of total examined). ~reteau

(2)

•

(3)

(c)

•

(d) (e)

index (number of positive containers per 100 houses).

Data obtained from such surveys can be subjected to computer analysis with subsequent production of valuable distribution maps by WHO. When correlated with distribution of cases observed at the same time it may be possible to determine the vector index levels that will or will not allow effective transmission of virus. ( 4)

Exchange of technical information is essential. Epidemiological reports including clinical, virological, and entomological data should be sent to the Epidemiological Surveillance and Quarantine, Geneva through the WHO Regional Offices.

•

- <!7/28 -

8. SUGGESTIONS AND COlNN'l'S The following suggestions were made by members of the seminar:

(1) (2)

Expedite the development of a live, attenuated virus vacc1ne for Japanese encephalitis. At the earliest opportunity, a working plan or blueprint should be devised for a field demonstration of the control of the dengue complex of ~ases by control of ~. aegypti in a city with a population of about 25 000 to 50 000 persons, where the diseases have been present for several years. The seminar was impressed with the results of the work of the WHO Aedes Research Unit in Bangkok and recOllJlllended that the larval control measures assessed by that unit should be employed. The f'ield demonstration should include assessments of' mosquito density, mosquito infection rates, and incidence of human disease. The working plan may best be devised by a small group of appropriate entomologists and epidemiologists oalled together by WHO. Prospective studies of Japanese encephalitis and dengue infections should include inter-epidemic periods. Inter-regional meetings of epidemiologists, clinicians, and other persons concerned with arbovirus infections should be encouraged at frequent intervals. ment of local laboratory diagnostic fa.cili ties. Ref'erence is made to the section above on Laboratory Diagnosis of Dengue Infections in regard to recommendations for improved diagnostic facilities and the use of cell cultures and safe, non-infectious antigens.

•

(3) (4)

(5) The need for technical training is noted in relation to the develop-

(6)

•

It is felt that the availability ot the insecticides abate and malathion, applied in the recommended ways, now makes it possible for effective Aedes control programmes to be instituted immediatel¥ in those countries that require control.

•

- 29/30 -

•

ANNEX I

NCE AN A SCHEMATIC ILWST RATIO N OF FACTORS WHICH INFLUE EPIDE MIC SIZE OF JAPANESE ENCEPHALITIS Build-up of ~ I ible , of suscept er amplifl I 1 amplifi er populat ion (swines. birds. I I etc.) __ - ____ __I 1

:-po;ulatio;;~

-1

1 '

INITIAL CYCLES BETWEEN VECTOR & AM'UFIER

Build-up of ~ vector

t~------------l t Meteorological factors I

(-"1

I

tempera ture humidity

~ I

I

po, , alion

i~'ul

------, ......

, ....

'" .... "!.I

•

I.. '" 1:1 ~ U)

., 9

;.

~

S

""J! :=

..

/U \ Exhaustion of sUlCeptible amplifi er

Massive occurrence of viraem ic

,--- --- ,

Mass ve ou1break 1 niSm Synchro , of L __ ,___ .J vectors

tation pl"ecipi ion of l process Seasona rice plantati on irrigation of I I rice paddies ~/- - - - - - - - -

I I I

l

- - --'

•

I

V NTER OF ENCOU VlRAEMIC AMPUFIER& VECTORS U INFECTION OF VECTOR MOSQUITOE1 ['1 PERIOD OF EXTRINSIC INCUBATION

, . I .,

c.

< ...,

e

J (-

~

--- --- -- --- .... - . . -1t Meteorological factors temperature humidity absence of typhoon .... _ o.!:-fl~ __ ' _ _ _

- - - - - ..~ 1

t I

•

MASSIVE EM:RGENCE OF TRANSMISSWLE MO rulTOES

I

4

~

•

.,t

1-~;;';lo'Sic;1 fu;to~ -

- --1 I

i : I

i

- - - -'Popul ation size of luscepd ble

.. -. ~

'j'

~

---

- -- J

l l- - - - - •

~ L

I

INFECTION OF SUSCEPTWLE HUMANS

which influence flight 8< biting activity t of vector mosquitoes I tempera ture l ty hUmidi I I

t

1

, I , I

!_~~g~2'i~ ~ - - - - -, 1 Ageing .1- - - _ . -I

, humans

,

'-r==IN"'"A':""P-P"':'A-RE::':N":"T:-t OR ABORTIVE ~ ONS

_ab~l!..ce

...oUY2.l1o.2.n _

--)

r-----....., I

•

""

f •

MAIN PROCESS OF lE VIRUS TRANSMISSl9J'! CYCLE }'O

MAN

Iii

•

- 31 ANNEX 2

LIST OF PARTICIPANTS LISTE DES PARI.'ICIPANTS Countries ~

Names of participants and addresses Noms des participants et adresses

WESTERN PACIFIC PACIFIQUE OCCIDENTAL AUSTRALIA AUSTRALIE Dr R.L. Doherty Director Queensland Institute of Medical Research Herston Road, Herston Queensland, Australia

• CHINA CHINE

Mr Lin Shen-yu 151 Tunghsing St., Nankang

Taipei, Taiwan Republic of China Dr Chang Li Wu !aipei Municipal Health Department 15 Chang-an West Road Taipei, Taiwan Republic of China

FIJI ILESFIWI

Dr J .U. Metaika Wellcome Virus Laboratory Colonial War Memorial Hospital SUY'a Dr J. Saugrain

•

FRENCH POLYNESIA POLYNESIE FRANCAISE

Institut de Recherches Medicales "Louis Malara.e" BP 30 Papeete. Tahiti

Polynesie JPlPAN

fran~aise

JAPON

Dr Akio Mi tsuhashi c/o The Chief Liaison Officer International Affairs Ministry of Health and Welfare 2-2, l-Chome, Kasumigaseki Chiyoda-ku, Tokyo Dr K.S. Chang Chief, Local Health Services Ministry of Health and Social Affairs Seoul

KOREA COREE

- 32 Countries ~

Names of participants and addresses Noms des participants et adresses Dr K.H. Kim Virologist National Institute of Health Seoul Dr Bhagwan Singh Senior Bacteriologist Institute for Medical Research Kuala Lumpur

KOREA COREE

MALAYSIA MALAISIE

Dr Lim Teong Wah

•

Institute for Medical Research Kuala Lumpur PAPUA AND NEW GUINEA PAPUA ET NOUVELLE-GUINEE Dr Michael A. Price Papuan Medical College P.O. Box 1034 Boroko, Papua Dr Guillermo S.D. Justiniano Medical Specialist II (Epidemiology) Bureau of Health Services Manila Dr Jane C. Baltazar Senior Epidemiologist Disease Intelligence Center Department of Health Manila VIET-NAM

PHTI..lPPINES

•

Dr Nguy8n-Duc-Hi8p 76 Trieu-Da Cholon, Saigon Dr Lanu Penaia Health Department Apia

WESTERN SAMOA SAMOA-OCCIDENTAL SOUTH-EAST ASIA ASJE

:ro

SUD-EST

CEYLON

Dr Yvette E. Hermon Medical Research Institute Colombo Dr SuJarti Jatanasen

THAlLAND THAILANDE

Communicable Disease Control Division Department of Health Bangkok

- 33 LIST OF CONSULTANTS AND ~RARY AD'lISER LISTES DES CONSULTANTS ET CONSElLLER TEMPORAIRE Dr W. McD. Hammon

Professor of Epidemiology and Microbiology Graduate School of rublic Health University of Pittsburgh, Pittsburgh Pennsylvania, 15213 United States of America Dr Albert Rudnick Arbovirus Research Laboratory Department of Bacteriology Faculty of Medicine University of Malaya Kuala Lumpur Malaysia Dr Vicente Reyes Pathologist San Lazaro Hospital Manila, Philippines

•

..

WHO SECRETARIAT SECRETARIAT DE l' OMS Dr A.C. Saenz Medical Officer Virus Unit WHO Headquarters Geneva

•

Dr B. Veilmirovic Regional Adviser on Communicable Diseases Western Pacific Regional Office Manila

Professor C.Y. Chow Regional Entomologist Western Pacific Regional Office Dr T. Okuno Medical Officer Communicable Disease Control Centre Taipei, Taiwan

- 34 LIST OF WHO OBSERVERS LISTE DES OBSERV ATEURS DE 11 OMS Dr B. Ignjatovic

RegIonal Adviser on Communicable Diseases Regional Office for South-East Asia New Delhi-l, India Dr A.W.A. Brown

Scientist/Biologist Vector Biology and Control WHO Headquarters, Geneva Dr R.J. Tonn Project Leader Japanese Encephalitis Vector Research Unit Seoul, Korea Dr Scott B. Halstead

Short-term Consultant Communicable Diseases Advisory Team Manila Dr G.M. Antal

Medical Officer Epidemiology and Statistics Advisory Service Seoul, Korea Dr A. Tito de Morais

Medical Officer Epidemiology and Health Statistics Phnom-Penh, Cambodia Dr A. Fedortchenko Medical Officer Communicable DiseaseS-General Activities Advisory Services Tarawa Gilbert and Ellice Islands Dr Y.H. Bang

WHO Entomologist WHO Aedes Research Un1 t Bangkok, Thailand

•

•

- 35 LIST OF OBSERVERS

LIS'rE DES OBSERVATEURS Names of observers and addresses Noms des observateurs et adresses PHlLIPPINES Dr Anastacia Fabie Medical Specialist I San Lazaro Hospital

Manila Dr Lino Edralin Lim

• FIFTH EPIDEKrOLOGICAL

161.4 Tayabas Corner Rizal Avenue Sta. Cruz, Manila

FLIGHT UNITED

STATES AIR FORCE

Major George D. Lathrop EpidemioLogist, USAF, Me 5th EpidemioLogical Flight

PHlLnrPINES

(PACAF) Department of the Air Force APO San Francisco 96528 United States of America Captain Stephen M. Va1.der Entomologist, USAF, BSC 5th EpidemioLogical Flight

[PACAF) Department of the Air Force APO San Francisco 96528 United States of America Commander Charles H. Sawyer

LTC, USAF, MC 5th Epidemiological Flight

(PACAF) Department of the Air Force APO San Francisco 96528 United States of America Captain Victor Schulz Chief of Virology 5th Epidemiological Flight

(PACAF) Department of the Air Force APO San Francisco 96528 United States of America

•

- 36 Names of observers and addresses Noms des observateurs et adresses FIFTH EPIDEMIOLOGICAL FLIGHT UNITED STATES AIR FORCE PHILIPPINES • Maj or

Seymour Wexler Chief of Microbiology 5th Epidemiological Flight (PAClJ!) Department of the Air Force APO San Francisco 96528 United States of America

UNITED STATES OF AMERICA ETATS-UNIS D' AMERIQUE

Dr W.G. Downs Yale Arbovirus Research Unit Yale University School of Medicine New Haven, Connecticut 06405 United States of America

..

UNITED STATES AGENCY FOR INrERNATIONAL DEVELOPME!NT (AID)

Dr John O. Stivers Chief Malaria Advisor USAID, Saigon Viet-Nam Dr Robert Juni Communicable Diseases Control Advisor USAID, Saigon Viet-Nam

THE V AN HOUWELING LABORATORY FOR MICROBIOLOGICAL RESEARCH

PHILIPPINES

Dr Francisco F. Macasaet Acting Director The Van Houweling Laboratory for Microbiological Research Silliman University Medical Center P.O. Box 49 Dumaguete City, J-409 Philippines

NATIONAL INSTITUTE OF HEALTH KOREA

Dr Nam He Chun

- 37 ANNEX 3 AGENDA

Date

Activity 08:00 09:00

6 October 1969

Registration Opening of the seminar Message

WHO Conference Hall

Dr Francisco J. Dy Regional Director

•

Agreement on agenda and time of session Appointment of Chairman, Vice-Chairman and Rapporteur Statement defining topics. definition and nomenclature of arboviruses 10:00 Japanese Encephalitis history and geographical distribution Sununary of country reports Summary of country reports (continuation) Dr B. Velimirovic

•

13:30 • 15:30

Epidemiological and clinical aspect Dr T. Okuno Pathogenesis Laboratory diagnosis Vaccines Discussions Dr T. Okuno Dr T. Okuno Dr A.C. Saenz

7 October 1969

08:00 10:00

13:30 15:30

Vectors and control Discussion

Dr A. Rudnick

Professor C.Y. Chow

..

- 38 -

-

Date

Activity

8 October 1969

08:00

History and geographical Dr B. Velimirovic distribution of denguecomplex Summary

10:00

of country reports

Epidemiology and clinical Dr W. MoD. Hammon aspects

13:30 15:30 9 Oetober 1969 08:00 10:00 13:30

Pathogenesis Patho:Logy of denguecomplex Laboratory diagnosis Prospect of vaccines Vectors and control Discussion

Dr S. Halstead Dr V. Reyes Dr W. McD. Ha!l!!!!l)ll DrW. McD. Hammon Dr A. Rudnick Dr R.J. Tonn

10 October 1969 08: 00 10:00

Murray Valley Encephalitis and Epidemic polyarthritis Viruses not yet related to diseases Epidemiological surveillance of arboviruses Aspects of international co-operation and WHO assistance Dr R.L. Doherty Dr A. Rudnick

•

13:30 15:30

n October 1969 11: 00

Final conclusions CLosing ceremony

•

•

TABLE 1 GROSS NECROPSY FINDINGS IN 100 CASES OF CLINICALLY-DIAGNOSED HAEIDRRHllGIC FEVER IN THE PHILIPPmS

HaemorHaemorrhages rhages petechial ecchymotic Skin Stomach Small intestine Mlrocardium Central nervous system Adrenal j;1;land Liver Serous cavity Lungs Kidneys Other areas 100 100 14

Hepatomegaly

Splenomegaly

Fatty changes

Serous effusion

Ulceration

Pneumonia

-

-

-

-

3

75 43 55

26 12 14 4

-

-

11 15

36

41

14

-

~ .j::' o \.>I

"38

1.6

44

-

31 47

9

-

3 2

9

-

010.

-

-

-

.

14

I

-

-

-

I

i

•

- 41/42 TABLE 2 ARBOVOOSES NOT YET RELATED 'ro RUMAN DISEASE IN THE WESTERN PACIFIC REatON (WHO). GEXlGRAPHICAL DISTRIBUTION AS J:Et.l)NSTRATED BY ISOLATION OF VIRtrS IN NA'l'URE

;:t a:I .p

<0

..-I [J)

a:I

Group A

Virus Bebaru

~ + +

'"'

"';)

~

:i

~ +

~

8 ~ ..-I a:I ~ ~

'C!

[J)

(J)

~ ..-I r-I

if ?

.....

U~ CIl

~ .....

'0"' ~ ~

t

EEE (1) B

?

Bakau Bluetongue Bunyamwera Koongol

•

Mapputta Simbuxx Wad Medani Ungrouped

Getah (Sagiyama) Whataroa Alfuy Apoi Edge Hill Kokobera KWljin Langat Stratford Tembusu Wesselsbron Zika Bakau Ketapang Bluetongue Batai Koongol Wongal Mapputta Truhanaman Akabane Seletar Corriparta Ephemeral Fever Eubenangee Kowanyama Lanjan

+ + + +

+

+ + + + + + + + + + + + + + + + + + + + + + +

+ + + +

+

*Not in ~ - neighbouring country XXOtber Simbu - related isolates from Japan and Australia are under study

•

•

TABLE 3

'

.

"

ARBOVIRUSES(l) NOT YE.'.r RILA'l'ED TO HUMAN DISEASE IN THE WES'l'ERN PACIFIC RmION (WHO) Demonstrable Antibody in man Disease in

Sero-group A

Virus Bebaru EEE (1)

Country or Territory(2) Malaysia Philippines (7), Thai land (1) Australia, Japan Malaysia, Ryukyus New Zealand Australia Japan Australia Australia Australia Mal.aysia Australia Malaysia Thailand Malaysia

Source Culex (Lophoceraomyia) spp. Monkey, Culex pipiens fatigans Culex tritaen1ornYnchus&. geli4us 2.. bi taeniorhynchus , Aedes vexans, ~. butleri, Anopheles !. amictus, pigs ~ pervigilans, Culiseta tonnoiri Swamp pheasant, AedO!!Wia catasticta Culex annul1rostris,Aedes vigilax, Anopheles meraukens1s Culex annulirostris annul1rostris, 2.. squ&mOsus, Oriolus flavocinctus Ixodes granulatus Aedes vigilax Culex tritaeniorhynchus,Q..gelidus Aedes lineatopennis , Anopheles philippineaais Aedes mediol1neatus, Aedes lineatopennis Aedes aegypti

man

Elsewhere

+ + +

Getah (Sagiyama)

Whataroa

+ 1 ? I

B

Al:f'uy

I

Apoi Edge Hill Kokobera Kunjin Langat Stratford Tembusu Wesselsbron Zika

~ ~ ~

curex

+

+ + (rare) ? ?

(4)

(3)

+ +

+ ( 5)

----

(1) Presence in region demonstrated by actual isolation of virus from naturally-infected source. (2) Thailand included as a close neighbour. (3) Febrile illness in two laboratory infections. ( 4) Experimental encephalitis produced in man. (5) One laboratory infection with illness reported in Africa. (6) other Simbu - related isolates from Japan and Australia under study.

•

•

•

'",

"

Table 3 (cont'd) Serogroup Bakau Bluetongue Bunyamwera Koongol Mapputta Group Simbu{b) Wad Madani Ungrouped Virus Bakau Ketapang Bluetongue Batai Koongol Wongal ( Mapputta ( Trubanaman Akabane Seletar Corriparta Ephemeral fever of cattle Eubenangee Kowanyama Lanjan Country or Territory(2) Source Culex (Lopbocerao!!\yia) spp., Culex sp. ~ (Lopboceraosria) spp. Vertebrate Culex gelidus J Aedes curtipes A. vexans Culex annulirostris Culex annulirostris Anopheles meraukensis Anopheles annulipes Culex tritaeniorhyncbus, Aedes vexans nipponii, Culicoides brevi tars is Boophilus microplus Culex annulirostris, wild birds Cattle Mosqui toes (11 mixed species) Anopheles annulipes, A. a. amictus Dermacentor auratus, HaemaphYsalis ~. JJemonstrable Antibody in man Disease in man I Elsewhere

Malaysia Malaysia Japan Malaysia, Thailand, Japan Australia Australia Australia Australia Japan, Australia Malaysia, Singapore Australia Australia, Japan Australia Australia Ma.l..aysia

+ + +

+

~ ~

oF

'l

+

•

•

•

II

•

IDENTJB;A'11ON OF AJ8QVIIIJSES lQIOWN TO OCCUR AND CAPABL6 OF CAUSING HJMAN DISEAIIIIN SWTH-EAST ASIA AND WBSTlRN PACJB; 1I!GJON

Vinal

Vm. GeopapllJal

lIolleed from

SeIoJoRY Odm C>Dr ~ftnee

Group A

Name Cblkun-

lAIc. . .

t.iIIl

OIlIer ftrIIIIbr. .

t.ecu

MID

\'ensbdlel

CIIaIca1 S)'DdIoma SA HuIlllDl

guay.

Mala'llia 1IIdones1a Pbilippioe$ CeyJDD

+

. + + fever, IOmedmes

wlch anbrltb ~.

MoIlley,

pig. Thallaad Viet-Ham India Camboclla SinUDCHe

+ +

~!!SII!!! ~!!8I2!!

9:!!!! fadp",

. .... + + +

bll1Cl1coot Horse. pilP

dengue-lile fever haamonbaglc fever

,

• +

I

-- .... VaUab1a ~ blrdi Gra111na cllIIlOllca

Roll River

Allltralia

£!!!!!. &IIIluliroatris

~~

.

~ Mammala 'lip. leangarooa& wallabies probable ca\118 of epidemic polyartbrltil

.$=:"

8i

virus New G\II.Dea Mlcroeca f&ICiDIDs

PoeebUa I!!noDAta SiDdbil Allltralia New Guinea Malaysia Pbilippinel --- -

£!!!!!. annuliroatris ~ oormaoenoll

+

blrdi

febrile illneU vesicular rash

+

Many domesdc anlmali

Culex siaeDIiI Culex ttiiieiiiorhync.hus

£!!!!!. tritaeniorhynchlll --

- ..

---~---------

•

•

•

•

4<

IDENTIFICATION OF ARBOVIRUSES KNOWN TO OCCUR AND CAPABLE OF CAUSING HUMAN DISEASE IN SOUTH"EAST ASIA AND WESTERN PACIFIC REGION Virus Group Virus Name Geographical lOCation Jsolared from Man Other vertebrates Serology Other Man vertebrares

-

MosquitoeS

Other insects

----I i

B

Dengue

1

x Japan

+

--

Philippines 1--1,2,3,4 Viet-Nam 1----Cambodia 1,2,4

------1,2,3,4 1 1,2,3,4

2,3,4

--

+ + + +

Aedes ~. Culex tritaeniorhynchus

-

-

+

monkey

------- 1---Aedes~,

+ +

Thailand Ceylon Malaysia

Aedes albOj2ictus

Singapore + - ---- -----:- f - : : - : - - - - - - - r---- 1 - - - - 1,2,3,4 India +

--

+ r--.-- ~-----monkey + I--

-- 1------------------'. + ----+ monkey --/----- ~-----

i

Aedes aemti, Aedes albol2ictus ~

+

-

--

1,2,3,4

Aedes~

aegyj2ti, Aedes alboj2ictus - -

---- ~-- 1--------------, + + --"~

+

-----

~

~

~

1-----

U1QOneslii

1,2,3 1,2,3,4 1,2

Australiax New Guinea Fiji

-

-

---

f--

-- --------------- --------------------- --- r------- --- 1------------ - , __________ . ___ .J ----------------- -------- '------ ~---------__ J - .._- ------------------------ ; - - - - -- I -- . ....! ._--------.-- --_._- -------------

---------- r----------

French Polynesia

1 1--

Pacific Islands Guarnx

----------------

+ 1------------1 -- 1------ 1------ t----- -- .. .. ------- -..".

I

_

-

I

-----

+

-----.

__

.-_ ..

I I i ,

i , xNo proven cases in the years WIder review. In Australia previously known epidemics. In New Guinea proven occurience in the World War

,

J

I

n and serological survey evidence in more recent infection.

'.

•

•

•

'I

~

IDENTIFICATION OF ARBOVlRUSES KNOWN TO OCCUR AND CAPABLE OF CAUSING HUMAN DISEASE IN SOUTH-EAST ASIA AND WESTERN PACIFIC REGION Virus Group Virus Name Geographical Location ,

Isolated from Man Other vertebrates birds, bats pig, hone ~

Serology Other insects Man Other vertebrate. Pig, birds horse

MJsquitoes tritaeniorhynchus

.

,_.".-,.

B

Japanese encepba-

Japan

+

+

litis USSR Korea Ryukyu Island Taiwan

+ + + Pig, snake

+ Culex tritaenior!!l::nchus Culex trltaeniorhynchus ~ ~

.. .. + Horse

uitaeniorhynchus, fuscosephalus

~~,

. . . + +

.

Pig, horse Pig, hone, cow, birds Pig, buffalo,goat, rabbit

Guamx Malaysia

9!!!:! gelidus,

..

Culex uitaeniorhynchus, Culex pseudovisrul'ui. M. uniformis, ~ butleri complex, Culex fuscosephalus, Aedes curtipes

:smgllpore PlUllppmesx India

-..--

Pig and many domestic animals wild boar l'

~ ~

\Jl

..

-

Culiax un:a.AlorhyDchua

+

9!!!:! tritaeniorhynchus Culex pseudovishnui Culex \-(hitinorei Culex tritaeniorhynchus ~gelidw

.. .. + + +

~

pig, goats

+ i

Thailand Viet-Nam Hong Kong Burma Ceylon -

. ..

i Pig. horse Pig. cow horse

l I

,

-

...

.

.. ..

x No proven cases in the years under review.

,,.

.

.. IIolateel from Other Man

•

¥

IDENTIFICATION OF ARBOVJRlJSES KNOWN TO OCCUR AND CAPABLB OF CAUSING HUMAN DISEASE IN SOUTH-EAST ASIA AND WESTBRN PACIFIC REGION

Virus Group

Virus Name

Geographical LocalioD

veltebratel wUeI bircls .

M:lsquitoel

Other insects

serology l>tber verteMan bra. .

Clinical Syndrome in Humlllll

AutbDr

Year

B

West Nne

JDd1a

+ + +

+ Culex annuUrostris

+ + + +

Murray valley encenbaUtis Kunjin

Australia New Guinea

----.

febrile lllness sometimes enceDbalitis birds,hor- encephaUtis ses,cattle birds febrile illness (lab. inf.)

+

Anderson

1954

-- .

1-.,---,--------Australia

bird (OrioIus fiavocinctus

Culex annulirostrb Culex Iguamosus

Doherty e tal.

1963

Zika RSSE

Malaysia USSR

~~

+

forest rocIent rocIents

.!!: 1l!:!!!cuIatus

+

Macaea not clefined nemestrina wilel anel encepbalomyeelomestic litis rocIents, birds, elomestic animals

Rullnick Silber

1968 1939 I·

~ ~ Work 1964

\J1

Kyasanur

tulia

beat cIiJeaIe

•

Macaca racliata, PreIb~

H. sp1nigera (licks) and others

+

rocIents, camel, birds

febrile illneu

clop ,horse 'With icterus and baemorrbage

enll:llus wilel rodens WesselsbroD PIRY

Thalland Inclia

+

+ horse, cat- Encephalitis tie, sheep, (2cuea) goat, monley VIC 1966

Cbanclipura

+

,

..

.

..

•

•

•

:-

•

REPORTED CASES OF JAPANESE BNCBPHALrrIS IN WBSTERN PACIFJ:; REGION. 1962-1968 --

Country CaleS

- --

... -

1962 Deam Cues

1963 Death CaleS

1964 Death CaleS

1965 Death CaleS

1966 Death Cues

1987 Death CaleS

1968 Death

Japan Kozea

1363 1038 7+

568 341 4+

1205 19

566 8

2565 2952 28:t

1312 966 8+

1119 152 5 .. 16

658 284 5+ ? 4 154

2301 3563 10+ 24 25

1500 965 6+ ? 2

1028 2013 15 .. 39 32 1024 190+ 31+ 3'7+

696 791 5+

292 1226 30

238

396

Malaysia

? 1 206

? 6 131 VI

Ryukyu lIlandJ Taiwan

99 412

21

120 699

24

66 444

1'1 9'1

22

33 610 22'7 + 41+ 96+

85

150

617 156+ lB+

819 215+ 40+

151

~

~ "

Viet-Nam

5+ 2+

NOlel

+Eatabl1sbed by aatlbocIy detection !Bqulvoca! or IUlpec!ed

7UaJawwn

... 19SI-lct52 1955

...

•

... 19# 1445

•

,

.

i

...

=J£

MAP NO. 1

I!!! 1111' 4 " ]E o

DISTRIBUTION OF ARBOVIRUSES IN THE WESTERN PAC IFIC AND SOUTH-EAST ASIA ACCORDING TO THE REPORTED CASES 1962-1969

I~~ JE 1969

•

6

"...

;:- () ]E 1947

~

•

1941-1~5

<I

~ ~~

~

.. ..

~ ~ ,

VI

0

~ ---~--

--.,~ ~1:>.

?

.-. IQ. 4

Japanese encephalitis (JE) Dengue complex (D) Japanese encephalitis in the past Dengue in the past No information Non-endemic area Chlkungunya Epidemi c polyarthritis Murray Valley encephalitis (one case since 1962)

~

\\",

DcfZ

~-(945

'1 .~

D

L94'3 1944

(JJ CH

•

-

1964 196<J