Evaluation of factors associated with positive IgM capture ELISA results in equids with clinical signs compatible with West Nile virus infection: 1,017 cases (2003).

The research examined the factors associated with West Nile virus (WNV) infection in equids, with a particular focus on understanding the relationship these factors have with positive results from an IgM capture ELISA test. The study suggested that gender, vaccination status, disease severity and geographic location in Colorado might influence the likelihood of testing positive for WNV in equids exhibiting clinical signs of the disease.

Methods

• The researchers obtained submission forms from the Colorado state veterinarian and diagnostic laboratories, which were used to collect data on the equids. The equids were all tested for WNV in Colorado in 2003.
• The data collected included the equid’s signalment (age, breed, sex), clinical signs, history of vaccination against WNV, and assay results.
• An important part of the methodology was the IgM capture ELISA, a test used to determine whether WNV is present in a sample. True positives were described as case equids.

Results

• The analysis was focused on a sample of 1,104 equids, of which 1,017 (92.1%) showed clinical signs that were compatible with WNV infection.
• Among these equids, males and those vaccinated against WNV had lower odds of testing positive via the IgM capture ELISA, compared to females and unvaccinated equids.
• Equids with moderate to severe illness had higher chances of testing positive compared to those with mild illness.

Conclusions

• The study concluded that vaccination against WNV, severity of the clinical signs, duration of illness, and region in Colorado were factors associated with an increased risk of testing positive for WNV.
• These findings suggest that these factors could influence the reliability of the IgM capture ELISA test in diagnosing WNV in equids.