Detection of West Nile virus-specific antibodies and nucleic acid in horses and mosquitoes, respectively, in Nuevo Leon State, northern Mexico, 2006-2007.

The study explores the presence of West Nile virus (WNV) in horses and mosquitoes in Nuevo Leon, Northern Mexico, during 2006 and 2007. Through testing via an epitope-blocking enzyme-linked immunosorbent assay and reverse-transcription PCR, the researchers found evidence of the virus in horses and two pools of Culex species mosquitoes, but not in Culex quinquefasciatus complex mosquitoes or other mosquito genera screened for flaviviruses.

Objective of the research

• The primary goal of this study was to investigate the presence and circulation of the West Nile virus in the Nuevo Leon state in Northern Mexico. Despite only one reported human case in the past five years, the researchers sought to determine whether the virus was still active in the region.

Methodology

• A total of 203 horses were tested for the West Nile virus using an epitope-blocking enzyme-linked immunosorbent assay (bELISA), a common method for detecting specific antibodies related to the virus.
• Apart from this, mosquito collections were also done in 2007 and yielded 7365 specimens that represented 15 species. These mosquitoes, primarily from the Culex genus, were tested for West Nile virus RNA.
• Other mosquito genera such as Mansonia, Anopheles, Aedes, Psorophora, and Uranotaenia were screened for flaviviruses using the reverse-transcription PCR method.

Findings

• The study found that 26% of the horses sampled in 2006 and 45% in 2007 had antibodies to the West Nile virus, indicating exposure to the virus.
• Two pools of mosquitoes from the Culex genus were found to contain West Nile virus RNA. However, molecular species identification revealed that these did not contain the Culex quinquefasciatus complex mosquitoes often associated with the virus.
• There was no evidence of flaviviruses in other mosquito genera examined.

Conclusion

• The study concludes that the West Nile virus is, indeed, circulating in Northern Mexico. The detection of virus RNA in non-Culex quinquefasciatus mosquitoes suggests that these species may also play a role in the virus transmission cycle in the region, expanding our understanding of the virus’ potential vectors.