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Emerging infectious diseases2003; 9(2); 161-168; doi: 10.3201/eid0902.020124

Equine amplification and virulence of subtype IE Venezuelan equine encephalitis viruses isolated during the 1993 and 1996 Mexican epizootics.

Abstract: To assess the role of horses as amplification hosts during the 1993 and 1996 Mexican Venezuelan equine encephalitis (VEE) epizootics, we subcutaneously infected 10 horses by using four different equine isolates. Most horses showed little or no disease and low or nonexistent viremia. Neurologic disease developed in only 1 horse, and brain histopathologic examination showed meningeal lymphocytic infiltration, perivascular cuffing, and focal encephalitis. Three animals showed mild meningoencephalitis without clinical disease. Viral RNA was detected in the brain of several animals 12-14 days after infection. These data suggest that the duration and scope of the recent Mexican epizootics were limited by lack of equine amplification characteristic of previous, more extensive VEE outbreaks. The Mexican epizootics may have resulted from the circulation of a more equine-neurotropic, subtype IE virus strain or from increased transmission to horses due to amplification by other vertebrate hosts or transmission by more competent mosquito vectors.
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Publication Date: 2003-02-27 PubMed ID: 12603985PubMed Central: PMC2901937DOI: 10.3201/eid0902.020124Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research examines the role of horses in the spread of a virus, specifically Venezuelan equine encephalitis (VEE), during outbreaks in 1993 and 1996 in Mexico, suggesting that inadequate equine amplification may have restricted the severity and length of these outbreaks.

Introduction

  • The research focuses on the Venezuelan equine encephalitis (VEE), a virus that mainly affects horses but can also infect humans.
  • The scientists wanted to understand the role of horses during the 1993 and 1996 VEE outbreaks in Mexico.
  • For this, they infected 10 horses with four different equine isolates.

Method

  • The horses were infected subcutaneously, meaning the virus was injected below the skin.
  • Most of the horses exhibited little to no signs of disease and also showed low or non-existent viremia.
  • Viremia refers to the presence of viruses in the bloodstream, suggesting that these horses were not efficient carriers of the virus.

Results

  • Only one horse developed neurological disease, and brain histopathologic examinations showed signs of infection.
  • Three animals displayed mild meningoencephalitis without clinical disease, which is an inflammation of the brain and the meninges, the protective membranes that envelop the brain and spinal cord.
  • Viral RNA was detected in the brains of several animals 12-14 days post-infection, meaning the virus was present but the animals were not necessarily displaying clinical signs of the disease.

Interpretation

  • These findings imply that the duration and scope of the 1993 and 1996 Mexican outbreaks were limited due to lack of equine amplification, which is characteristic of larger, more severe outbreaks.
  • The term “equine amplification” refers to the role of horses in the spread of the virus, in this case, the horses did not significantly contribute to the spread of the virus.
  • The outbreaks in Mexico may have been a result of a more equine-neurotropic strain of the VEE virus, meaning a version of the virus with a greater preference for invading and affecting the nervous system of horses.
  • Alternatively, the outbreaks could have been impacted by increased transmission to horses through other vertebrate hosts or more competent mosquito vectors, meaning mosquitoes that are better at spreading the virus.

Cite This Article

APA
Gonzalez-Salazar D, Estrada-Franco JG, Carrara AS, Aronson JF, Weaver SC. (2003). Equine amplification and virulence of subtype IE Venezuelan equine encephalitis viruses isolated during the 1993 and 1996 Mexican epizootics. Emerg Infect Dis, 9(2), 161-168. https://doi.org/10.3201/eid0902.020124

Publication

Emerging infectious diseases
ISSN: 1080-6040
NlmUniqueID: 9508155
Country: United States
Language: English
Volume: 9
Issue: 2
Pages: 161-168

Researcher Affiliations

Gonzalez-Salazar, Dante
  • Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias, Mexico City, Mexico.
Estrada-Franco, José G
    Carrara, Anne-Sophie
      Aronson, Judith F
        Weaver, Scott C

          MeSH Terms

          • Animals
          • Brain / virology
          • Communicable Diseases, Emerging / genetics
          • Encephalitis Virus, Venezuelan Equine / genetics
          • Encephalitis Virus, Venezuelan Equine / isolation & purification
          • Encephalitis Virus, Venezuelan Equine / pathogenicity
          • Encephalomyelitis, Venezuelan Equine / epidemiology
          • Encephalomyelitis, Venezuelan Equine / veterinary
          • Encephalomyelitis, Venezuelan Equine / virology
          • Gene Amplification
          • Histocytochemistry
          • Horse Diseases / blood
          • Horse Diseases / epidemiology
          • Horse Diseases / virology
          • Horses
          • Leukocyte Count
          • Mexico / epidemiology
          • Mice
          • Platelet Count
          • RNA, Viral / isolation & purification
          • Temperature
          • Virulence

          Grant Funding

          • R01 AI048807 / NIAID NIH HHS
          • AI39800 / NIAID NIH HHS
          • AI48807 / NIAID NIH HHS

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          Citations

          This article has been cited 19 times.
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