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Western equine encephalomyelitis: virulence markers and their epidemiologic significance
T I Bianchi1, G Aviles, T P Monath
1Institute of Virology, Faculty of Medical Science, National University of Cordoba, Argentina.
Abstract:
Comparative studies are described on the virulence of the western equine encephalomyelitis (WEE) complex viruses for mice. Three epizootic WEE virus strains (McMillan, Cba 87, and Cba CIV 180) and five enzootic WEE complex viruses (Highlands J [HJ], Y62-33, Aura, Fort Morgan [FM], and WEE AG80-646) were examined. The neurovirulence and the neuroinvasiveness of these viruses for adult mice were established and correlated with viremia and virus replication in brain tissue. Adult mice inoculated intraperitoneally showed differential responses that corresponded to the epidemiologic attributes of WEE viruses. Viruses associated with equine epizootics were neurovirulent and neuroinvasive, whereas enzootic viruses were neither neuroinvasive nor neurovirulent. In North America, HJ virus appears to be an antigenic link with an intermediate virulence between epizootic WEE virus and the enzootic FM virus. The HJ virus has been associated with rare cases of sporadic equine and human diseases. In South America, no virus with intermediate virulence characteristics has been described. We speculate that epizootics may arise from nonpathogenic strains such as AG80-646 maintained in enzootic transmission cycles.
Insights
Epizootic western equine encephalomyelitis (WEE) viruses are neurovirulent and neuroinvasive in mice, unlike enzootic strains. Highlands J virus shows intermediate virulence, potentially linking epizootic and enzootic WEE virus strains.
Area of Science:
- Virology
- Neuroscience
- Epidemiology
Background:
- Western equine encephalomyelitis (WEE) is a significant arboviral disease affecting equines and humans.
- Understanding the virulence of different WEE virus strains is crucial for disease control and prevention.
Purpose of the Study:
- To compare the neurovirulence and neuroinvasiveness of epizootic and enzootic WEE virus strains in mice.
- To correlate viral characteristics with epidemiological attributes and disease potential.
Main Methods:
- Comparative analysis of three epizootic and five enzootic WEE virus strains.
- Intraperitoneal inoculation of adult mice.
- Assessment of neurovirulence, neuroinvasiveness, viremia, and brain virus replication.
Main Results:
- Epizootic WEE viruses demonstrated significant neurovirulence and neuroinvasiveness.
- Enzootic WEE viruses were neither neuroinvasive nor neurovirulent.
- Highlands J virus exhibited intermediate virulence, acting as a potential antigenic link.
- Differential responses in mice correlated with the epidemiological profiles of WEE viruses.
Conclusions:
- WEE virus virulence in mice reflects its epidemiological role.
- Epizootic strains pose a greater threat due to neuroinvasiveness and neurovirulence.
- Nonpathogenic enzootic strains may serve as reservoirs for potential epizootic emergence.