Natural Vertical Transmission of WNV in Montana

West Nile Virus (WNV) emerged and rapidly spread throughout the United States within several years. WNV is spread in Montana primarily by the mosquito vector Culex tarsalis. Horizontal transmission of WNV has been extensively studied, while little is known regarding vertical transmission. Previous research suggests vertical transmission is possible in controlled laboratory studies. This research attempts to document natural vertical transmission in Montana. Larvae were collected and analyzed for WNV via RTPCR. Results show no presence of natural vertical transmission. Culex larvae and adult male mosquito collection methods were insufficient, fluctuations in temperatures and variant rainfall were contributing factors. Future directions should examine methods to improve collection of Culex larvae. Gravid traps infusions attracting gravid Culex tarsalis mosquitoes may be a promising direction to investigate