Which best describes the transmission of West Nile virus in the United States?

The transmission of West Nile virus is best described by the fact that it cycles primarily between mosquitoes and birds. This is a key aspect of its epidemiology. Mosquitoes are the primary vectors that acquire the virus when they feed on the blood of infected birds. Infected mosquitoes can then transmit the virus to other birds, as well as other animals (including horses and humans) through their bites.

This cycle highlights the importance of birds in the transmission dynamics of West Nile virus, as they serve as the main reservoir for the virus. While the virus can occasionally infect mammals, it is predominantly a bird-mosquito-bird transmission cycle.

In contrast, the other options do not accurately describe the transmission dynamics of West Nile virus. For instance, the virus is not primarily transmitted through rodent contact, as they are not significant reservoirs for this particular virus. Additionally, the notion of being highly contagious among domestic animals does not pertain to West Nile virus, as its transmission does not occur rapidly among those populations. Lastly, while there are vaccines available for certain animals, the effectiveness of these vaccinations does not eliminate the need for integrated vector control measures, as the primary means of transmission is through the mosquito-bird cycle.