North American Veterinary Licensing Examination (NAVLE) Practice Test

The primary mode of transmission of West Nile Virus (WNV) between birds is via mosquitoes. Mosquitoes serve as vectors for the virus, facilitating its spread from infected birds to other avian species and also to mammals, including humans. When a mosquito bites an infected bird, it takes up the virus and can transmit it during subsequent bites to other birds. This cycle is crucial for the maintenance and amplification of the virus within bird populations, which are the primary reservoirs for WNV.

Other options provided do not reflect the actual transmission mechanisms of WNV among birds. Cnemidocoptes mites, which are parasitic mites, do not play a role in the transmission of WNV. Similarly, saliva transmission is not a characteristic method for this virus; instead, mosquitoes are the key transmitting agents. The transmission via the placenta is typically relevant to certain other pathogens in different contexts and is not applicable to the manner in which WNV spreads in avian hosts.