Arbovirus Studies in the Guajira Region of Venezuela: Activities of Eastern Equine Encephalitis and Venezuelan Equine Encephalitis Viruses during an Interepizootic Period *

Abstract

Repeated outbreaks of Venezuelan equine encephalitis (VEE) in humans and equines in the Guajira region of Venezuela suggested a sylvatic focus of an epizootic subtype of VEE virus. A surveillance system was established, and virus isolations were attempted from 67,760 mosquitoes as well as sentinel hamsters. Sixteen isolates of eastern equine encephalitis (EEE) and a strain of Itaqui virus were recovered from mosquitoes, and 60 isolates of EEE, two of VEE, and two of Itaqui viruses were recovered from tissues of sentinel hamsters. The VEE virus isolates were shown to be closely related antigenically to prototype VEE ID and the EEE virus isolates were shown to be more closely related to the South American than the North American variety of EEE virus. Evidence for the presence of VEE and EEE viruses in small wild vertebrates was obtained from serologic testing. This study showed, for the first time, the enzootic presence of both VEE ID and EEE viruses during a nonepizoodemic period in the Guajira region.

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

“…38 Other mammals, such as opossums (Didelphis marsupialis) are also frequently infected with enzootic VEE viruses in a variety of locations. 30,31,[39][40][41] The high rate of VEE virus antibodies we found in Proechimys guairae is consistent with the conclusions of previous studies that these spiny rats are important reservoir hosts of enzootic VEE viruses. 37 We also detected antibodies in two Didelphis marsupialis, consistent with previous results in Venezuela.…”

“…37 We also detected antibodies in two Didelphis marsupialis, consistent with previous results in Venezuela. 30,31 To our knowledge, Marmosa spp. have not previously been implicated as enzootic reservoirs of VEE virus.…”

“…Surveillance in this region of Miranda State, assisted by satellite imagery, has not revealed the presence of any extensive, primary lowland tropical forests or swamps like those known to support continuous transmission of VEE viruses in other locations of South Ameri-ca. 15,[29][30][31][32][33][34] Studies are now underway to locate such a transmission cycle in Falcon State, where the 1995 outbreak began.…”

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

“…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. 10 traps, 23 or from mosquitoes captured in these traps.…”

Genetic and antigenic diversity among eastern equine encephalitis viruses from North, Central, and South America.

“…Multiple isolations of EEEV from the subgenus Culex (Melanoconion) in South and Central America have implicated these mosquitoes as potential enzootic vectors. 1 Antibody prevalence indicates that small mammals 14 and birds 15,16 serve as enzootic reservoir hosts. Isolates of EEEV from the Caribbean have been serologically and genetically identified as members of the North American antigenic variety, most likely introduced by migratory birds from the United States.…”