Re-emergence of epidemic Venezuelan equine encephalomyelitis in South America
Open accessAbstract
BACKGROUND: Venezuelan equine encephalomyelitis (VEE) virus has caused periodic epidemics among human beings and equines in Latin America from the 1920s to the early 1970s. The first major outbreak since 1973 occurred in Venezuela and Colombia during 1995, and involved an estimated 75,000 to 100,000 people. We report an epidemiological and virological investigation of this epidemic. METHODS: Virus isolates were made in cell culture from human serum, human throat swabs, and brain tissue from aborted and stillborn human fetuses, as well as from horse brain tissue and pooled mosquito collections. Human sera were also tested for VEE-specific antibodies. The serotypes of VEE isolates were identified by antigen assays, and viruses were characterised genetically by sequencing PCR products generated from the E3 and E2 genes. Phylogenetic analyses were done to determine evolutionary relations with respect to previous epidemic/epizootic and enzootic VEE virus isolates. Mosquito collections were made to identify possible vectors, and clinical findings were determined by direct observation of patients visiting hospitals and clinics in affected regions, and by inspecting patient records. Equine vaccination and vector control were used in an attempt to halt the spread of the outbreak. FINDINGS: Most affected people had an acute, self-limited febrile illness of 3 to 4 days duration. However, convulsions were often seen in children, and abortions and fetal deaths occurred in pregnant women infected with VEE virus. Antigenic characterisation of 12 virus isolates spanning the temporal and spatial range of the outbreak indicated that all are VEE serotype IC. Phylogenetic analysis revealed that all of the 1995 viruses were closely related to serotype IC viruses isolated during a large VEE outbreak that occurred in the same regions of Colombia and Venezuela from 1962-1964. A 1983 mosquito isolate from north central Venezuela was also closely related to the 1995 isolates. INTERPRETATION: This outbreak was remarkably similar to one that occurred in same regions of Venezuela and Colombia during 1962-1964. Symptoms of infected patients, estimated mortality rates, meteorological conditions preceding the epidemic, and seasonal patterns of transmission were all very similar to those reported in the previous outbreak. In addition, viruses isolated during 1995 were antigenically and genetically nearly identifical to those obtained during 1962-1964. These findings suggest that the epidemic resulted from the re-emergence of an epizootic serotype IC VEE virus. Identification of a similar virus isolate in mosquitoes in Venezuela in 1983, 10 years after epidemic/epizootic VEE activity ceased, raises the possibility of a serotype IC enzootic transmission cycle in northern Venezuela.
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Aedes taeniorhynchus bites during both day and night and is an important vector of canine heartworm (Dirofilaria immitis) and Venezuelan encephalitis.
“The species bites during both day and night and is an important vector of canine heartworm (Dirofilaria immitis) and Venezuelan encephalitis [25,26].”
From North American Wetlands and Mosquito Control (2012) · cites this paper as [26]
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“The species bites during both day and night and is an important vector of canine heartworm (Dirofilaria immitis) and Venezuelan encephalitis [25,26].”
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- Authors
- Weaver, S. C., Salas, R., Rico-Hesse, R., Ludwig, G. V., Oberste, M. S., Boshell, J., & Tesh, R. B.
- Affiliations
- The University of Texas Medical Branch at Galveston (US)
- Yale University (US)
- United States Army Medical Research Institute of Infectious Diseases (US)
- Corresponding author
- Weaver, Scott C
- Venue
- The Lancet
- Publisher
- Elsevier BV
- Published
- 1996-08
- Volume
- 348
- Issue
- 9025
- Pages
- 436-440
- ISSN
- 0099-5355 (ISSN-L)
- 0140-6736
- OpenAlex
- W2097935692
- Cited by
- 285
- References
- 22
- Citations by year
- 2026: 1 · 2025: 8 · 2024: 7 · 2023: 8 · 2022: 9 · 2021: 7 · 2020: 11 · 2019: 6 · 2018: 7 · 2017: 11 · 2016: 7 · 2015: 8 · 2014: 13 · 2013: 9 · 2012: 12
- FWCI
- 8.73
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- The Lancet (publishedVersion, cc-by-nc-nd)
- PubMed (publishedVersion)
- Funders
- National Institutes of Health (5r29ai039508-03, 5r01ai033983-04)
- National Institute of Allergy and Infectious Diseases (AI39508, AI 33983, AI-10894)
- Topics
- Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Mosquito-borne diseases and control
- Health Sciences › Medicine › Infectious Diseases › Viral Infections and Vectors
- Health Sciences › Medicine › Epidemiology › Virology and Viral Diseases
- Keywords
- Venezuelan equine encephalomyelitis, viral re-emergence, antigenic characterisation, mosquito vectors, equine vaccination, vector control, seasonal transmission, South America
- MeSH terms
- Adolescent, Adult, Animals, Child, Child, Preschool, Colombia, Disease Outbreaks, Encephalitis Virus, Venezuelan Equine, Encephalomyelitis, Venezuelan Equine, Female, Horse Diseases, Horses, Humans, Infant, Middle Aged, Molecular Sequence Data, Pregnancy, Venezuela
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