In the United States, the vector reservoir for agents causing viral encephalitis is which of the following?

• A. Tarantula spiders.
• B. Carnivorous wild animals.
• C. Domestic and wild animals.
• D. Mosquitoes and ticks.

Answer: (D)

Transmission of viral encephalitis in the United States occurs primarily through arthropod vectors—mosquitoes and ticks. Mosquitoes transmit several encephalitis viruses, including West Nile, St. Louis, and Eastern and Western equine encephalitis. A tick-borne example is Powassan virus, spread by Ixodes ticks. Tarantula spiders do not carry these viruses, and while domestic and wild animals can serve as reservoirs, they are not the vectors that pass the virus to humans. So, the agents causing viral encephalitis in the U.S. are transmitted by mosquitoes and ticks.