Which combination serves as the secondary vector and secondary reservoir for St. Louis Encephalitis (SLE)?

Which combination serves as the secondary vector and secondary reservoir for St. Louis Encephalitis (SLE)?

• A. Cx. pipiens and wild birds
• B. Ae. aegypti and horses
• C. Cx. tarsalis and humans
• D. An. gambiae and domestic cats

Answer: (A)

St. Louis encephalitis virus is kept in nature by an exchange between birds and mosquitoes. Birds are the reservoir hosts that maintain the virus, while mosquitoes transmit it between birds and can occasionally infect people. Among mosquitoes, some species mainly feed on birds and serve as secondary vectors, helping move the virus around within the bird–mosquito cycle. Culex pipiens fits this role well because it readily feeds on birds and can bridge transmission to humans when needed. So pairing a Culex species that targets birds with wild birds as the reservoir reflects the secondary vector–reservoir dynamic of SLE. The other options involve mosquitoes not typically implicated in SLE transmission or vertebrates that do not sustain the virus in nature (horses, humans, cats).

St. Louis encephalitis virus is kept in nature by an exchange between birds and mosquitoes. Birds are the reservoir hosts that maintain the virus, while mosquitoes transmit it between birds and can occasionally infect people. Among mosquitoes, some species mainly feed on birds and serve as secondary vectors, helping move the virus around within the bird–mosquito cycle. Culex pipiens fits this role well because it readily feeds on birds and can bridge transmission to humans when needed. So pairing a Culex species that targets birds with wild birds as the reservoir reflects the secondary vector–reservoir dynamic of SLE. The other options involve mosquitoes not typically implicated in SLE transmission or vertebrates that do not sustain the virus in nature (horses, humans, cats).