Andrea Townsend

Mosquito blood-feeding patterns and nesting behavior of American crows, an amplifying host of West Nile virus,” co-authored by Associate Professor of Biology Andrea Townsend, was recently published in the journal Parasites & Vectors.

The paper presents the results of research that helps explain why, though crows are highly susceptible to West Nile virus and show a high mortality rate after infection, their importance in the transmission cycle of the virus has been questioned “because of their consistent underrepresentation in studies of Culex [mosquito] blood meal sources.”

To find a possible reason for this underrepresentation, Townsend and researchers from the Sacramento-Yolo Mosquito and Vector Control District, Cornell University, and the University of California, Davis, studied a group of crows in Davis, Calif., to “examine how the likelihood of a crow blood meal changes with distance to and timing of active crow nests.”

Over a four-month period, using mosquitos collected at varying distances from the crow nesting sites, the researchers used genotypes “from crow blood meals and local crows … to match mosquito blood meals to specific local crows.”

Among the results of the study, they found that blood meals of crow origin were greatest during the crow nesting period in late spring and that “the likelihood of a crow blood meal increased with proximity to an active nest.”

They said that roosting behavior might also be important in West Nile virus transmission and that “underrepresentation of roosts in mosquito sampling designs could contribute to the underrepresentation of crows among blood meal studies.” They noted that examination of the timing of breeding of other hosts and proximity to communal roosts might further explain the importance of crows in West Nile virus transmission.

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