Which mosquito is the primary vector for La Crosse encephalitis?

• A. Aedes Triseriatus
• B. Culex quinquefasciatus
• C. Anopheles gambiae
• D. Aedes aegypti

Answer: (A)

La Crosse encephalitis is transmitted mainly by Aedes triseriatus, the eastern tree-hole mosquito. This species naturally breeds in small, sheltered water collections like tree holes, and it maintains the virus in an enzootic cycle by feeding on small mammals such as chipmunks and squirrels. Humans become infected when they're bitten by an infected mosquito, making this mosquito the key bridge between the animal reservoir and people. Aedes triseriatus is also capable of vertical transmission, helping the virus persist in mosquito populations across generations even if vertebrate hosts are scarce.

The other mosquitoes listed are associated with different diseases or regions. Culex quinquefasciatus is a vector for other encephalitides such as West Nile and St. Louis encephalitis, not the primary La Crosse vector. Anopheles gambiae is known for malaria transmission. Aedes aegypti transmits dengue, Zika, and yellow fever. While other mosquitoes can play roles in some areas, the principal vector for La Crosse encephalitis remains Aedes triseriatus.