Yellow fever: evolution of ideas concerned with demonstrating the natural occurrence of transovarial transmission of virus in mosquitoes

In November 1978, an outbreak of disease among wild simians of south Trinidad alerted officials to the presence of jungle yellow fever (YF). Learning of the epizootic and having recently been involved in studies establishing transovarial transmission (TOT) of YF virus, this laboratory urged Trinidad workers to undertake demonstration of the natural occurence of TOT in the forest environment. The idea as well as a suggested procedural protocol involving vector mosquitoes (Haemagogus spp.) was accepted and acted upon. Initial procedures called for undertaking studies in areas where sick or dead monkeys were observed, collecting larvae as well as adult female Haemagogus from which eggs were to be obtained, hatched, and the ensuing larvae reared to adults and tested for virus. As time passed, various problems were encountered necessitating changes in field procedures. The most important was the substitution of ovitraps for adult female collections as a source of eggs. By 1980, the epizootic/epidemic was waning. Funding for additional studies became available from Canadian sources and the author was invited to be a consultant. Field and laboratory procedures were again modified and streamlined. Described are: (1) choice of field sites, (2) choice of ovitraps, (3) siting of ovitraps, (4) frequency of collections, (5) laboratory procedures, (6) search for male Haemagogus and female ovipositing activity, and (7) duration of a TOT study and conclusions.

Jungle yellow fever mosquito studies in Trinidad: 1954

Eruption of a yellow fever epizootic/epidemic was signalled by the Trinidad Regional Virus Laboratory with the isolation of virus from the first human case in April 1954. Mosquito investigations were conducted in three major areas. Descriptions are provided of the forest environments, the mosquito collection techniques, transportation logistics, mosquito identification and isolation of viruses. An addendum briefly reviews subsequent yellow fever outbreaks in the island, addresses the question of origin and provides recommendations for the future.