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.

Sylvatic yellow fever activity in Trinidad 1988-1989

Of a total of 18,068 mosquitoes (361 pools) collected in south-eastern Trinidad forests from December, 1988 to May, 1989, 47 species belonging to 14 genera were identified. Five yellow fever virus isolates were made from Haemagogus janthinomys and one from Sabethes chloropterus. All the other pools of mosquitoes examined were negative for the virus. The mosquito isolates were made in December and January. In addition, in late February and early March, two infected howler monkeys (Alouatta sp.) were detected. Since March, despite continued surveillance, no yellow fever virus has been detected in mosquitoes or monkeys. There has been no reported human infection.

Yellow fever studies in Trinidad, 1988-1989: attempts to demonstrate Transovarial Transmission of yellow fever virus in Haemagogus mosquitoes collected in nature

Subsequent to an epizootic of yellow fever (YF) in monkeys and the isolation of yellow fever (YF) virus from sylvatic mosquitoes in December, 1988 and January, 1989 in south-east Trinidad, ovitrapping for mosquito eggs was started in January, 1989, in an attempt to demonstrate transovarial transmission of the virus. Multi-paddle ovitraps were used. From a total of 52,632 eggs collected in various parts of the country, the following species of mosquitoes were reared: Haemagogus janthinomys (54 per cent ), Hg. leucocelaenus (32 per cent ), Aedes insolitus (12 per cent ), Hg. equinus (1 per cent ). When mosquito eggs were removed from the hard board paddles then vacuum-treated for hatching, the process proved very economical in storage space. Most eggs were obtained at the start of the wet season, four to five months after the isolation yellow fever virus from wild caught adult mosquitoes and monkey carcasses. When adult mosquitoes reared from eggs were processed for yellow fever virus, no virus was detected from any of the mosquito pools to indicate that transovarial transmission had occurred.