A mosquito (Diptera: Culicidae) model for the transmission of tularemia

Abstract

Tularemia is a plague-like disease caused by the bacterium Francisella tularensis. In Scandinavian countries tularemia transmission is clinically attributed to mosquitoes. To examine the transmission of tularemia by mosquitoes I exposed Aedes aegypti and Anopheles gambiae larvae to F. tularensis and tested all life stages for bacterial DNA using real-time polymerase chain reaction (rtPCR). I fed adult A. aegypti and An. gambiae a blood meal containing F. novicida and tested for DNA 24, 48 and 72 hours after feeding. Seventy-two hours after the F. novicida blood meal I allowed A. aegypti and An. gambiae to feed on a mouse. My results indicate that 1. Aedes aegypti and An. gambiae larvae ingest F. tularensis but eliminate it from their system before maturing to adults and, 2. F. novicida DNA is present in adults 72 hours after feeding, and 3. mice remained healthy after multiple mosquitoes feeding on them. Although this implies F. tularensis is not spread by A. aegypti and An. gambiae, it exemplifies the need to investigate other subspecies of F. tularensis and other species of mosquito to eliminate species dependence.