Ecological studies of enzootic Venezuelan equine encephalitis in north-central Venezuela, 1997-1998.

Abstract

Abstract. From 1997From -1998, we investigated the possible continuous circulation of epizootic Venezuelan equine encephalitis (VEE) virus suggested by a 1983 subtype IC interepizootic mosquito isolate made in Panaquire, Miranda State, Venezuela. The study area was originally covered by lowland tropical rainforest but has been converted into cacao plantations. Sentinel hamsters, small mammal trapping, mosquito collections, and human serosurveys were used to detect active or recent virus circulation. Six strains of subtype ID VEE virus were isolated from hamsters that displayed no apparent disease. Four other arboviruses belonging to group A (Togaviridae: Alphavirus), two Bunyamwera group (Bunyaviridae), and three Gamboa group (Bunyaviridae) arboviruses were also isolated from hamsters, as well as 8 unidentified viruses. Venezuelan equine encephalitis-specific antibodies were detected in 5 small mammal species: Proechimys guairae, Marmosa spp., and Didelphis marsupialis. Mosquito collections comprised of 38 different species, including 8 members of the subgenus Culex (Melanoconion), did not yield any virus isolates. Sera from 195 humans, either workers in the cacao plantation or nearby residents, were all negative for VEE virus antibodies. Sequences of 1,677 nucleotides from the P62 gene of 2 virus isolates indicated that they represent a subtype ID lineage that is distinct from all others characterized previously, and are unrelated to epizootic VEE emergence.

Genetic diversity and relationships among Venezuelan equine encephalitis virus field isolates from Colombia and Venezuela.

“…8 The strains from Miranda State were closely related to the Yumare isolate, also from northern Venezuela in Yaracuy State. As described previously, 18 this lineage of ID viruses is distinct from all others identified previously and is not closely related to epizootic VEE viruses.…”

“…This area was originally covered by lowland tropical rainforest that has been converted into cacao (Theobroma cacao) plantations. 18 The other enzootic Venezuelan sites are tropical lowland forests in the Catatumbo region of western Venezuela 19,20 and near Sinamaica in the southern part of the Guajira Peninsula. 21 The 22 hamsters housed in modified Trinidad no.…”

Contrasting sylvatic foci of Venezuelan equine encephalitis virus in northern South America.

“…12,36 Candidate mosquito species to export enzootic or epizootic VEE virus mutants out of the enzootic foci should exhibit the following criteria: 1) abundance in both open areas and forests, 2) a wide range of vertebrate host contacts, 3) ability to disperse over long distances, and 4) competent vectors of enzootic and/or epizootic VEE virus. The most common mosquito species captured in open areas and in the forests in this study were Ae.…”

“…11,12 However, only the first ID genotype is linked to epizootic emergence, which is probably related to the genetic background of the enzootic precursors and their ability to generate appropriate combinations of epizootic mutations. 11 Enzootic subtype ID VEE virus circulating during the past 30 years in the Catatumbo region of Venezuela and the middle Magdalena Valley of Colombia are members of the ID lineage with a history of generating epizootic subtype IAB or IC VEE virus via small numbers of mutations.…”

Short report: Isolation and identification of Venezuelan equine encephalitis virus from a human in Panama.

“…The primary vectors for the ID subtype virus are believed to be Culex mosquitoes of the subgenus Melanoconion and small ground rodents serving as the principle reservoir hosts. 7,8 This type of habitat would make control measures aimed at the vectors or reservoir hosts nearly impossible to achieve. The viral strains of the ID subtype are of particular interest since studies have indicated that spo- If the patient was exposed at Gatun Lake, the disease would have required an extraordinary long incubation period of approximately 10 days before onset.…”