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Carrie Nielsen Wins Reeves New Investigator Award for Mosquito Research

Carrie Nielsen tracking the West Nile virus in Davis. (Photo by Kathy Keatley Garvey)

DAVIS—Carrie Nielsen, a University of California, Davis doctoral student who last year tracked the West Nile epidemic in Davis as it occurred, has received the statewide William C. Reeves New Investigator Award for her work.

Nielsen, an epidemiology doctoral candidate in the Arbovirus Research Program of the UC Davis Center for Vectorborne Diseases (CVEC), received the $1000 prize at the recent Mosquito and Vector Control Association of California (MVCAC) conference in Fresno.

Making the presentation was UC Davis medical entomologist Gregory Lanzaro, director of the UC Mosquito Research Program and CVEC. MVCAC and the UC Mosquito Research Program coordinate the annual award.

“Carrie did an excellent job in tracking the West Nile virus epidemic in Davis,” Lanzaro said, “and we congratulate her.”

The Reeves New Investigator Award, memorializing world-renowned medical entomologist William C. Reeves (1916-2004) of UC Berkeley, is awarded to the best scientific paper submitted and presented at the annual MVCAC conference.

Nielsen studies with CVEC research entomologist William Reisen, principal investigator of the UC Mosquito Research Program-funded grant, “Do Corvid Roosts Affect the Risk of Urban West Nile Virus Transmission in California?”

Nielsen’s research paper, “Impacts of Adult Mosquito Control and Climate Variation on the West Nile Virus Epidemic in Davis during 2006,” is part of her five-year doctoral dissertation, “The Epidemiology of West Nile Virus in the Sacramento Valley.”  She researches the vectors (Culex mosquitoes), the hosts (birds, but especially corvids or crows and magpies) and incidental hosts (humans and horses).

At the MVCAC conference, Nielsen discussed how a degree-day model she conducted enabled her to predict WNV activity. “Warmer nights, not warmer days, are necessary for the amplification of the WNV transmission to occur,” she said.  Culex mosquitoes, which transmit WNV, are active at dawn and dusk.

The aerial spraying of adulticides over Davis helped break the transmission of the virus, she found. The spraying occurred as night temperatures were decreasing.

Nielsen helped conduct the 2006 Davis Dead Bird Surveillance program, aimed at understanding the distribution of Culex vectors of WNV and how they affect the transmission dynamics within varying land uses in the urban community.

Under the surveillance program, UC Davis researchers picked up dead birds reported in the Davis area from April to October. Technicians at the California Animal Health and Food Safety Laboratory System necropsied the birds, and CVEC technicians tested them for the West Nile virus.

Last year, Yolo County was a state epicenter for WNV, with 27 human cases reported  and 54 birds testing positive for the virus.  Of the 276 human cases in California, Kern County ranked first with 49, followed by Butte with 31 and Yolo, 27.

The UC Mosquito Research Program, founded in 1972, is a statewide program of the UC Agriculture and Natural Resources.