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

Abstract

Abstract. During field studies of enzootic Venezuelan equine encephalitis (VEE) viruses associated with epizootic emergence, a large number of virus isolates were made in sylvatic foci of Venezuela and Colombia. To rapidly characterize these isolates, antigenic subtypes were determined by means of immunofluorescence and by single-strand conformational polymorphism (SSCP) analysis by use of an 856-bp fragment from the P62 gene, which we used to distinguish genetic variants. Representative isolates were sequenced to assess the sensitivity of SSCP to detect genetic differences. The SSCP analysis distinguished isolates differing by as little as 1 nucleotide; overall, differences of Ն 1 nucleotide were recognized 89% of the time, and the sensitivity to distinguish strains that differed by only 1 or 4 nucleotides was 17 and 57%, respectively. Phylogenetic analyses of representative sequences showed that all recent isolates from the Catatumbo region of western Venezuela and the middle Magdalena Valley of Colombia were closely related to epizootic subtype IAB and IC strains; strains from Yaracuy and Miranda States were more distantly related. Cocirculation of the same virus genotype in both Colombian and Venezuelan foci indicated that these viruses are readily transported between enzootic regions separated by Ͼ 300 km. The SSCP analysis appears to be a simple, fast, and relatively efficient method of screening VEE virus isolates to identify meaningful genetic variants.

Generation and Characterization of Closely Related Epizootic and Enzootic Infectious cDNA Clones for Studying Interferon Sensitivity and Emergence Mechanisms of Venezuelan Equine Encephalitis Virus

“…ZPC738 was isolated from the heart of a sentinel hamster exposed in a tropical lowland forest of Zulia State, Venezuela, in 1997 (15,28). The strain was characterized antigenically as a subtype ID with monoclonal antibodies as described previously (21).…”

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

“…13 Thus, the forests with a scarcer host and vector fauna, where VEE virus is more difficult to isolate, exhibited a greater genetic diversity of viruses than the Colombian forest where VEE virus circulates at higher levels. This could reflect greater fragmentation of the virus populations in the Venezuelan Catatumbo, providing more opportunities for allopatric divergence of virus lineages in different foci of transmission.…”

“…Two slightly different genetic VEE virus variants within this ID lineage have been found co-circulating in the same forests of the Catatumbo area, and one of these also occurs in the Magdalena Valley of Colombia. 13 The strongest genetic and geographic link between enzootic and epizootic viruses is represented by one of these variants, which is found in two different forests of the Catatumbo region and is closely related to the epizootic IC VEE emergence of 1992−1993 in western Venezuela. 10,13 Contrasting the transmission dynamics of subtype ID VEE virus between the Colombian and Venezuelan foci could contribute to our understanding of the emergence of new epizootic VEE virus variants.…”

“…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. 9,13 These VEE virus enzootic foci include lowland forests of the Catatumbo (Venezuela) and Magdalena (Colombia) River basins (350 km apart), and viruses isolated there are closely related to the epizootic subtype IAB and IC VEE virus emergences that affected both countries since the early part of the 20th century. Two slightly different genetic VEE virus variants within this ID lineage have been found co-circulating in the same forests of the Catatumbo area, and one of these also occurs in the Magdalena Valley of Colombia.…”

“…13,[15][16][17] Differences in virus diversity and isolation rates between the two areas may be related to variations in weather, and ecologic differences in vectors and hosts involved in the natural transmission cycle. A detailed comparison of the Colombian versus Venezuelan foci is pertinent because the landscapes in both areas appear similar upon superficial examination, with equivalent land-use patterns (cattle ranching, oil extraction), vegetation (pastures, patches of tall lowland tropical forests, limited agriculture), drainage (close to major rivers), and terrain slope.…”