The control of hookworm disease in Commonwealth Caribbean countries.

Like other countries around the globe where conditions existed for the parasites causing hookworm disease to thrive, this disease was a serious problem to settlers in countries of the Commonwealth Caribbean, i.e. those countries that were formerly part of the British Empire. Early in the 20th century, the Rockefeller Foundation (RF) assisted the southern United States in controlling this disease. Soon other countries requested assistance and the Rockefeller Foundation responded by creating their International Health Commission to target the problem. Guyana (then British Guiana) was the first country where work was started. Through a system of chemotherapy, sanitation with the provision of latrines and health education the RF assisted the Commonwealth Caribbean countries during the period 1914-1925 in controlling the disease. Most countries continued the programmes started by the Rockefeller Foundation and this paper provides evidence through a series of surveys to show that hookworm disease is no longer a public health problem.

The hunt for Caribbean viruses: a history of the Trinidad Regional Virus Laboratory

This is a brief story of the Trinidad Regional Virus Laboratory-TRVL-sometimes called "Travail". The story, of course, is well known to arbovirologists and entomologists around the world but the story is not well known amongst Caribbean Health Officials and the lay public. This is an attempt to fill this gap. It is not intended to be an analytical account but the story is told as it unfolded. Evidence that TRVL was internationally recognised (AU)

The hunt for Caribbean viruses: a history of the Trinidad Regional Virus Laboratory

This is a brief story of the Trinidad Regional Virus Laboratory-TRVL-sometimes called "Travail". The story, of course, is well known to arbovirologists and entomologists around the world but the story is not well known amongst Caribbean Health Officials and the lay public. This is an attempt to fill this gap. It is not intended to be an analytical account but the story is told as it unfolded. Evidence that TRVL was internationally recognised

Seasonal abundance, biting cycle and parity of the mosquito Haemagogus leucocelaenus in Trinidad, West Indies

Adult female populations of Haemagogus leucocelaenus (Dyar and Shannon), the sylvan vector of yellow fever, were monitored weekly during 1981-82 by human collectors on the ground at Point Gourde in Chaguaramas Forest, 16 km west of Port-of-Spain, Trinidad. Hg.leucocelaenus showed only diurnal landing activity, from 06.00 to 18.00 hours (sunrise to sunset, universal time), with a single peak of activity between 10.00 and 14.00 hours. Densities of Hg.leucocelaenus during the wet season (May-November) were about double the level recorded during the dry season (December-April). Monthly parous rates averaged 53.9 percent (range 25-90 percent) and some females were up to five pars. Retained eggs (range 2-6, mean 4/female) were found in the ovaries of 0.34 percent of landing females, all of which had stage 1 ovarian follicles for the next gonotrophic cycle. Therefore blood-feeding is not inhibited by egg retention. Hg.leucocelaenus vector potential is reappraised in the light of these findings (AU)

Seroprevalence of toxocara infections in schoolchildren in the Eastern Caribbean - abstract

Very little is known about the prevalence of Toxocara infections in the Eastern Caribbean. The development of the enzyme-linked immunosorbent assay (ELISA) has proved to be of great value in assisting clinicians in diagnosing toxocariasis and has been a useful tool in the study of the prevalence of toxocariasis. We have used ELISA to study the prevalence of toxocariasis in six countries of the Eastern Caribbean. The secretory-excretory antigen and reference sera for the assay were obtained from the University of Toronto. Test sera were collected from school children aged 5 years and 9 years from Antigua, Montserrat, Dominica, St. Vincent, St. Christopher-Nevis and Grenada. These sera were collected for polio antibody prevalence surveys and were stored in our serum bank. Sera with a titre of 100 or more were considered positive for Toxocara. Overall prevalence rates were: Antigua - 38.8 percent (n=322), Montserrat - 47.4 percent (n=228), Dominica - 59.9 percent (n=157), St. Vincent - 63.2 percent (n=285), St. Christopher-Nevis - 66.1 percent (n=168) and Grenada - 78.0 percent (n=387). Although antibody prevalence was high, no full-blown cases of visceral larva migrans have been reported in these countries. The public health significance of these findings is unclear (AU)

Significant reductions in the rates of gastrointestinal tract parasitic infections in children of St. Vincent over a thirteen-year period (1979-1992) - abstract

When 314 (1979) and 207 (1992) five- to nine-year old school children in St. Vincent were investigated for the presence of parasitic infections, there were significant reductions in the prevalence of trichuriasis (75 per cent to 21.7 per cent), ascariasis (37 per cent to 8.6 per cent), amoebiasis (9 per cent to 2.8 per cent) and giardiasis (10 per cent to 5.3 per cent) over the 13-year interval. Anthelminthic use remained at 63 - 65 per cent, but the brands of worm medicines taken changed over the period. Thus, whilst piperazine citrate was used by 41 per cent of the children in 1979, only 4.8 per cent of them used it in 1992. Albendazole which was used by a great majority (42.5 per cent) in 1992 was never used in 1979. Commensals were observed in 211 (67 per cent) children in 1979, and in 83 (40 per cent) children in 1992 (AU)

Significant changes in gastrointestinal tract parasitic infections in children of St. Kitts over the 9-year period 1982-1991

When 239 (1982) and 361 (1991) five-year and nine-year-old children in St. Kitts were assessed for the presence of parasitic infections, there were significant reductions in the prevalence of trichuriasis from 83 per cent to 58 per cent , of ascariasis from 24 per cent to 8.6 per cent and of giardiasis from 15 per cent to 9 per cent . Anthelminthic use, which appeared to be the most important responsible intervention tool, remained roughly at the same level at 59-51 per cent . However, the types of anthelminthics used changed over the period. Piperazine citrate, which was used by 66 per cent in 1982, only had 35 per cent usuage in 1991. Albendazole which was not used at all in 1982 was taken by 32 per cent of the children in 1991 and at the same time the use of laevo-tetramisole increased by 20 per cent from 14 per cent . Suggestions are made for an island-wide mass intervention programme to manage parasitic infections.

Significant changes in gastrointestinal tract parasitic infections in children of St. Kitts over the 9-year period 1982-1991

When 239 (1982) and 361 (1991) five-year and nine-year-old children in St. Kitts were assessed for the presence of parasitic infections, there were significant reductions in the prevalence of trichuriasis from 83 percent to 58 percent, of ascariasis from 24 percent to 8.6 percent and of giardiasis from 15 percent to 9 percent. Anthelminthic use, which appeared to be the most important responsible intervention tool, remained roughly at the same level at 59-51 percent. However, the types of anthelminthics used changed over the period. Pizerazine citrate, which was by 66 percent in 1982, only had 35 percent usuage in 1991. Albendazole which was not used at all in 1982 was taken by 32 percent of the children in 1991 and at the same time the use of laevo-tetramisole increased by 20 percent from 14 percent. Suggestions are made for an island-wide mass intervention programme to manage parasitic infections. (AU)

Changes in gastrointestinal tract parasitic infections in St. Kitts children - abstract

When 239 (1982) and 361 (1991) 5- and 9-year-old children in St.Kitts were assessed for the presence of parasitic infections there were significant reductions in the prevalence of trichuriasis from 83 percent to 58 percent, of ascariasis from 24 percent to 8.6 percent and of giardiasis from 15 percent to 9.4 percent. Health education appeared to be the most important responsible intervention tool. Anthelmintic use remained roughly at the same level. However, the types of anthelmintics used changed over the period. Piperazine citrate, which was used by 66 percent in 1982, only had 35 percent usage in 1991. Albendazole which was not used at all in 1982 was taken by 32 percent of the children in 1991, and, at the same time, use of laevotetramisole increased by 20 percent from 14 percent (AU)

Laboratory colonization and maintenance of Toxorhynchites moctezuma

A colony of Toxorhynchites moctezuma was established at the Caribbean Epidemiology Centre in Trinidad in 1984. Toxorhynchites moctezuma was maintained in cages with high humidities. Eggs were deposited most frequently in a cut bicycle tire containing water. A minimum of 42 h was required for hatching, but 94 percent hatched between 43 and 51 h. Aedes aegypti larvae were supplied as prey. Larval development times varied with the quantity of prey offered, but when fed ad lib, peak developmental time was 18 days. Mean pupal developmental time was 5.5 days. Although only 12 percent of larvae survived to pupation in 3 years of production, our experience indicates this species would be a likely candidate for mass production and release.(AU)

Seasonal incidence and diel oviposition periodicity of Haemagogus mosquitoes (Diptera: Culicidae) in Trinidad, W.I. Part III. Haemagogus celeste (Dyar and Nunez Tovar) and Haemagogus leucocelaenus (Dyar and Shannon).

The seasonal incidence and diel oviposition patterns of sylvan Haemagogus celeste and Hg. leucocelaenus in the Pt. Gourde Forest, Trinidad, were monitored weekly for 53 consecutive weeks using conventional ovitraps. During the dry season peak oviposition by Hg. celeste occured between 10:00 and 12:00 hours, and that by Hg. leucocelaenus between 12:00 and 14:00 hours; during the wet season peak oviposition by both species occurred between 12:00 and 14:00 hours. Diurnal patterns of oviposition were observed for both species during the wet and dry seasons. The numbers of ovipositions and of eggs laid during the wet season were, for both species, significantly higher (P greater than 0.001) than those observed during the dry season. (AU)

Studies on the natural history of yellow fever in Trinidad

Papers on yellow fever activity in Trinidad and Tobago presented by a total of 27 authors. An historical perspective is represented. Areas covered range from the surveillance of yellow fever in Trinidad, vaccination campaigns during the epidemic, arboviral studies of the Trinidad Regional Virus Laboratory, laboratory diagnosis of yellow fever and entomological issues

Laboratory diagnosis of yellow fever infections in humans, alouatta monkeys and haemagogus mosquitoes in Trinidad, 1978-1980

The yellow fever epidemic in Trinidad began with an epizootic in alouatta monkeys in November, 1978. Activity was detected by virus isolation from Alouatta monkeys and from Haemagogus mosquitoes between this date and July 1980. First reports of monkey deaths centered around the Guayaguayare forests of South Trinidad, following which the epizootic spread west to the Moruga area, and north through the Biche Forest reserve, eventually reaching the north-west Chaguaramas peninsula. Surveillance of febrile persons attending clinics and hospitals was intensified and 18 confirmed cases were identified, from 14 of whom yellow fever virus was isolated. In four cases, diagnoses were made on the basis of liver pathology only. Paired sera were obtained from 10 of 11 persons who survived, and in each case serological conversions were obtained by haemagglutination inhibition and mouse neutralization tests. Yellow Fever virus was isolated from 16 of 32 Alouatta monkeys and from 19 of 174 pools of Haemagogus mosquitoes. Two systems were used for virus isolation: the Aedes cell line AP-61 and suckling mice. The former proved to be more sensitive, detecting virus in 11.7 per cent of 725 specimens inoculated whereas suckling mice detected virus in 7.9 per cent of 724 specimens. In 11 instances virus was detected in an animal or mosquito pool by AP-61 but not initially by mouse inoculation whereas the converse was true in only one case.

Entomological activities during the yellow fever epidemic in Trinidad, 1978-1980

An epidemic of sylvan yellow fever occurred in Trinidad during the period 1978 to 1980. Entomological activities were initiated at various localities where monkey (Alouatta spp.) mortalities were reported. A total of 5,468 Haemagogus janthinomys was collected and tested which resulted in the isolation of 17 strains of yellow fever virus. Two strains of the virus were isolated from a total of 49 Haemagogus leucocelaenus and these constituted the first isolations of yellow fever virus from this species of mosquito from Trinidad. Attempts to demonstrate transovarial transmission of yellow fever virus from adults feared from eggs and larvae collected in the field were unsuccessful. However, from two locations virus isolations were made at the end of rainy season (January) and at the beginning of the successive rainy season (June).

Seasonal and vertical distribution of ovipositing Haemagogus mosquitoes in Trinidad

Ovitraps and bamboo pots were used to monitor the seasonal and vertical distribution of ovipositing female Haemagogus mosquitoes in the Moruga forest, south Trinidad. Over a one-year period 12,499 eggs were recovered in all months of the year, but the majority were collected in the rainy season. Peak collections were made in the early part of the rainy season. Haemagogus larvae were not collected in January and February, but thereafter there was a steady increase in collections reaching a peak in September with 390. The mean number of eggs oviposited per positive trap per month was 25.82. Of the 12,499 eggs collected 29.94 per cent hatched to either Hg. janthinomys or Hg. leucocelaenus. Both species of eggs were found in traps placed throughout the vertical at two tree stations in 1979.

Studies on yellow fever in inter-epizootic period in Trinidad

Following an outbreak of yellow fever in Trinidad in 1978-1979, a study was undertaken to investigate the jungle reservoirs and vectors of yellow fever virus in the inter-epizootic period, to seek evidence of natural transovarial transmission of yellow fever virus in Haemagogus collected. These were made four months after the last detection of virus in that area of the island and could not positively be attributed to transovarial transmission. None of the 42,815 progeny of wild mosquitoes yielded virus. No yellow fever virus was isolated from 34,300 mosquitoes other than Haemagogus nor from 15 vertebrates collected in areas of former virus activity. Good progress was made in optimizing the use of the AP-61 cell line resulting in rapid isolation and identification of dengue and yellow fever viruses from Caribbean countries.

Aedes aegypti surveillance at the airports in Trinidad and Tobago: an eight year study

A Programme of surveillance for Aedes aegypti mosquitoes was instituted at the airports of Trinidad and Tobago following an epidemic of yellow fever in 1978. The Surveillance system consisted of the use of ovitraps to collect Ae. aegypti eggs. After a period of eight years and the examination of 54,136 ovitrap paddles, 53 paddles were found positive. Only one of the positives came from Tobago. In Trinidad, ovitraps set in the car park and areas easily accessible to the general public were the ones most frequently found positive for Ae. aegypti eggs. The quick detection of positive paddles and close liaison with the Ministry of Health allowed prompt treatment of the affected areas, reducing the risks of possible transport of these mosquitoes by aircraft to other countries.

Studies on the natural history of yellow fever in Trinidad

This small monograph is more than simply a collection of papers about yellow fever, it is also an expression of the origins of the Caribbean Epidemiology Centre (CAREC). Although many early accounts recorded in these pages cannot be scientifically authenticated, research this century suggests a cyclic pattern of epizootics with occasional outbreaks of human disease. The natural cycle of the disease involves monkeys and mosquitoes but mysteries remain to be elucidated, such as where does the virus go between epizootics. Transovarial transmission among mosquitoes may be important, while other mammalian and insect species might also be involved. Such questions are raised in these pages

Aedes aegypti surveillance at the airports in Trinidad and Tobago: an eight year study

A Programme of surveillance for Aedes aegypti mosquitoes was instituted at the airports of Trinidad and Tobago following an epidemic of yellow fever in 1978. The Surveillance system consisted of the use of ovitraps to collect Ae. aegypti eggs. After a period of eight years and the examination of 54,136 ovitrap paddles, 53 paddles were found positive. Only one of the positives came from Tobago. In Trinidad, ovitraps set in the car park and areas easily accessible to the general public were the ones most frequently found positive for Ae. aegypti eggs. The quick detection of positive paddles and close liaison with the Ministry of Health allowed prompt treatment of the affected areas, reducing the risks of possible transport of these mosquitoes by aircraft to other countries (AU)

Studies on yellow fever in inter-epizootic period in Trinidad

Following an outbreak of yellow fever in Trinidad in 1978-1979, a study was undertaken to investigate the jungle reservoirs and vectors of yellow fever virus in the inter-epizootic period, to seek evidence of natural transovarial transmission of yellow fever virus in Haemagogus collected. These were made four months after the last detection of virus in that area of the island and could not positively be attributed to transovarial transmission. None of the 42,815 progeny of wild mosquitoes yielded virus. No yellow fever virus was isolated from 34,300 mosquitoes other than Haemagogus nor from 15 vertebrates collected in areas of former virus activity. Good progress was made in optimizing the use of the AP-61 cell line resulting in rapid isolation and identification of dengue and yellow fever viruses from Caribbean countries (AU)