Prevalence of antibodies against Saint Louis encephalitis and Jamestown Canyon viruses in California horses.

This study sought to establish the prevalence of antibodies against Jamestown Canyon (JC) and Saint Louis encephalitis (SLE) viruses amongst horses in California, before the introduction of West Nile virus. The researchers found antibodies to JC virus in approximately 15% of the tested horses, whereas no antibodies were detected against SLE virus.

Study Purpose and Methodology

• The overarching goal of this research was to investigate the seroprevalence (the level of a pathogen in a population, as measured in blood serum) of antibodies against Jamestown Canyon and Saint Louis encephalitis viruses in California’s horse population.
• The reason for carrying out this study was to establish a baseline prevalence prior to the introduction of West Nile virus, another mosquito-generated disease that affects horse populations.
• For the study, serum samples were taken from 425 horses across 44 horse operations in California in 1998. These samples were then tested for the presence of JC and SLE virus antibodies.

Research Findings

• Around 15% of the serum samples had antibodies to the JC virus. This suggests that, prior to 1998, horses in California were frequently infected with mosquito-transmitted Bunyaviruses that are identical or closely related to the JC virus.
• No antibodies were detected against SLE virus, showing that it was not prevalent in the horse population of California during the study period.

Interpretation and Implications

• The discrepancy in seroprevalence of SLE and JC viruses likely mirrors the unique ecological characteristics of each virus. These characteristics involve factors such as the viruses’ reservoirs, vectors, and modes of transmission.
• The results of this study may have implications in understanding the implications of the West Nile virus. It is predicted that the West Nile virus may have a broader distribution in California than the closely related SLE virus.
• Identifying the seroprevalence of these viruses can also help in managing and preventing future outbreaks by understanding the susceptibility and immune response of the horse population to these viruses.