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

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.

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

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