Search for Epizootic-Like Venezuelan Encephalitis Virus at Enzootic Habitats in Guatemala During 1969–197112

Scherer, William F.; Anderson, Kathleen S.; Pancake, Bette A.; Dickerman, Robert W.; Ordóñez, José V.

doi:10.1093/oxfordjournals.aje.a112262

Cited by 15 publications

(4 citation statements)

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“…8 An epizootic strain of VEEV was collected in Guatemala in an enzootic habitat in 1969, but this occurred during the 1969-1971 Central/ North American outbreak. 9 Navarro and others 10 also detected post-epizootic persistence of a VEEV subtype IC strain in Venezuela on cattle ranches 5 years after the apparent end of the 1995 outbreak. Additional surveillance in western Venezuela to determine if IAB strains continue to circulate there is warranted.…”

Section: Resultsmentioning

confidence: 90%

Genetic Diversity of Venezuelan Alphaviruses and Circulation of a Venezuelan Equine Encephalitis Virus Subtype IAB Strain During an Interepizootic Period

Medina¹,

Garzaro²,

Barrios³

et al. 2015

The American Journal of Tropical Medicine and Hygiene

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Abstract. Several species of alphaviruses have been previously described in the Americas, some of which are associated with encephalitis and others are associated with arthralgia. Venezuelan equine encephalitis virus (VEEV) and eastern equine encephalitis virus (EEEV) are endemic to Venezuela, with the former being responsible for major outbreaks of severe and often fatal disease in animals and humans. The aim of this study was to analyze the genetic diversity of Venezuelan alphaviruses isolated during two decades of surveillance in northern Venezuela. Phylogenetic analysis indicated the circulation of a VEEV subtype IAB strain 8 years after the last reported outbreak. Thirteen strains within two subclades of South American lineage III of EEEV were also found in Venezuela. Considerable genetic variability was observed among Venezuelan Una virus strains, which were widely distributed among the clades. The first Venezuelan Mayaro sequence was also characterized.

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Section: Resultsmentioning

confidence: 90%

Genetic Diversity of Venezuelan Alphaviruses and Circulation of a Venezuelan Equine Encephalitis Virus Subtype IAB Strain During an Interepizootic Period

Medina¹,

Garzaro²,

Barrios³

et al. 2015

The American Journal of Tropical Medicine and Hygiene

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“…Extensive hydroxylapatite chromatography and plaque size analyses of enzootic virus isolates have been used to search for epizootic subpopulations (30,31,34). Stanick et al (34) examined 23 different ID virus strains but were unsuccessful in detecting any epizootic phenotype variants.…”

Section: Discussionmentioning

confidence: 99%

Potential Sources of the 1995 Venezuelan Equine Encephalitis Subtype IC Epidemic

Brault

Powers

Medina

et al. 2001

J Virol

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Venezuelan equine encephalitis viruses (VEEV) belonging to subtype IC have caused three (1962-1964, 1992-1993 and 1995) major equine epizootics and epidemics. Previous sequence analyses of a portion of the envelope glycoprotein gene demonstrated a high degree of conservation among isolates from the 1962-1964 and the 1995 outbreaks, as well as a 1983 interepizootic mosquito isolate from Panaquire, Venezuela. However, unlike subtype IAB VEEV that were used to prepare inactivated vaccines that probably initiated several outbreaks, subtype IC viruses have not been used for vaccine production and their conservation cannot be explained in this way. To characterize further subtype IC VEEV conservation and to evaluate potential sources of the 1995 outbreak, we sequenced the complete genomes of three isolates from the 1962-1964 outbreak, the 1983 Panaquire interepizootic isolate, and two isolates from 1995. The sequence of the Panaquire isolate, and that of virus isolated from a mouse brain antigen prepared from subtype IC strain P676 and used in the same laboratory, suggested that the Panaquire isolate represents a laboratory contaminant. Some authentic epizootic IC strains isolated 32 years apart showed a greater degree of sequence identity than did isolates from the same (1962-1964 or 1995) outbreak. If these viruses were circulating and replicating between 1964 and 1995, their rate of sequence evolution was at least 10-fold lower than that estimated during outbreaks or that of closely related enzootic VEEV strains that circulate continuously. Current understanding of alphavirus evolution is inconsistent with this conservation. This subtype IC VEEV conservation, combined with phylogenetic relationships, suggests the possibility that the 1995 outbreak was initiated by a laboratory strain.Venezuelan equine encephalitis viruses (VEEV) are singlestranded, message-sense RNA alphaviruses (Togaviridae) with a genome of approximately 11 kb (32, 35). The genome encodes four nonstructural proteins (nsP1 to nsP4) comprising the 5Ј two-thirds of the genome (nucleotide positions 1 to 7514), and three structural proteins (capsid, E2, and E1 envelope glycoproteins) are encoded by a subgenomic message identical to the 3Ј one-third of the genome. VEEV are transmitted among vertebrate hosts by mosquitoes and are serologically classified into six antigenic subtypes (I to VI). These viruses can also be classified into two distinct epidemiological types. Only epizootic/epidemic viruses in antigenic subtypes IAB and IC have been responsible for major, sporadic outbreaks of human and equine disease (44). In contrast, enzootic VEEV in subtypes ID, IE, IF, and II-VI are transmitted continuously in sylvatic foci among small mammalian reservoir hosts by mosquito vectors in the Culex (Melanoconion) subgenus (44). Although these enzootic viruses can cause severe human illness like epizootic strains (12, 46), they are not efficiently amplified by equines and have therefore not been associated with major epidemics. Epizootic VEEV (subtypes IAB an...

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“…The equine virulence of several IE strains isolated previous to the recent Mexico epizootics has been studied in naturally and experimentally infected horses and burros, but there was no definitive evidence of VEE virus subtype IEinduced pathogenesis in any of the animals inoculated peripherially. [37][38][39][40][41] Nevertheless, VEE virus subtype IE was isolated from encephalitic horses in Mexico in 1993 and 1996, 10 and indirect evidence suggested the association of VEE virus subtype IE with a small equine epizootic in Mexico in 1966. 4,5 It remains to be determined whether differences in virus and/or vector populations, underlying health conditions in the horses, or other factors may potentiate VEE virus subtype IE-induced equine disease and whether this virus subtype may be emerging as an important veterinary pathogen in Mexico and Central America.…”

Section: Discussionmentioning

confidence: 99%

Geographic distribution of Venezuelan equine encephalitis virus subtype IE genotypes in Central America and Mexico.

Oberste

Schmura

Weaver

et al. 1999

The American Journal of Tropical Medicine and Hygiene

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Phylogenetic analysis of 20 strains of Venezuelan equine encephalitis (VEE) virus subtype IE isolated from 1961 to 1996 in Mexico and throughout Central America showed that VEE virus subtype IE was monophyletic with respect to other VEE virus subtypes. Nonetheless, there were at least three distinct geographically separated VEE virus IE genotypes: northwestern Panama, Pacific coast (Mexico/Guatemala), and Gulf/Caribbean coast (Mexico/ Belize). Strains from the Caribbean coast of Guatemala, Honduras, and Nicaragua may cluster with the Gulf/Caribbean genotype, but additional isolates from the region between Guatemala and Panama will be required to firmly establish their phylogenetic position. Viruses associated with two separate equine epizootics in Mexico in the 1990s were phylogenetically related to nonepizootic viruses from neighboring Guatemala and may represent the emergence or re-emergence of equine-virulent VEE virus subtype IE in Middle America.Venezuelan equine encephalitis (VEE) virus, a member of the alphavirus genus of Togaviridae, is a major arboviral pathogen of the western hemisphere, causing large-scale outbreaks among humans and equines in tropical and subtropical regions of the Americas. 1 The VEE viruses have been classified into six major subtypes (I-VI) based on antigenic characteristics, with additional variants defined within subtypes I and III. 2 Variants IAB and IC are equine-virulent and have caused large equine outbreaks in northern South America throughout the latter two-thirds of the 20th century, including a 1969-1971 VEE virus subtype IAB epizootic that swept through Central America and Mexico, and into southern Texas in the United States. 3 The remaining VEE viruses (ID-IF and II-VI) are maintained in localized enzootic foci in close association with a preferred mosquito vector and small mammal host. The enzootic strains have traditionally been considered to be avirulent for equine species, based on experimental infections, but most are fully capable of causing human disease. 1 The VEE virus subtype IE has been isolated from mosquitoes or sentinel rodents in Mexico and throughout Central America. In the 1960s, there were several small-scale equine encephalitis outbreaks in northeastern Mexico, prior to the northward movement of VEE virus subtype IAB. 4,5 Although no etiologic agent was isolated, the outbreaks were clinically compatible with VEE virus etiology and it has been suggested that the local enzootic VEE virus IE strain was responsible. 5 In southeastern Mexico, human and equine VEE virus infections were detected serologically, 6-8 but virus isolates were obtained only from mosquitoes and from sentinel hamsters. 9 In 1993 and 1996, VEE virus subtype IE was isolated from diseased horses during two small-scale epizootics of equine encephalitis on the southwest coast of Mexico in Chiapas (1993) and Oaxaca (1996) states, resulting in a total of 160 known cases. The viruses isolated during those outbreaks were antigenically indistinguishable from other IE strains and partial nuc...

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Search for Epizootic-Like Venezuelan Encephalitis Virus at Enzootic Habitats in Guatemala During 1969–197112

Cited by 15 publications

References 0 publications

Genetic Diversity of Venezuelan Alphaviruses and Circulation of a Venezuelan Equine Encephalitis Virus Subtype IAB Strain During an Interepizootic Period

Genetic Diversity of Venezuelan Alphaviruses and Circulation of a Venezuelan Equine Encephalitis Virus Subtype IAB Strain During an Interepizootic Period

Potential Sources of the 1995 Venezuelan Equine Encephalitis Subtype IC Epidemic

Geographic distribution of Venezuelan equine encephalitis virus subtype IE genotypes in Central America and Mexico.

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