| Risk Assessment and Management Solutions for Arthropod-borne and Infectious Diseases |
RAMS-AID Research - Mosquitoes and West Nile Virus disease in Colorado
Culex tarsalis and West Nile virus disease in the Front Range: Seasonal risk
| The seasonal peak in abundance of Culex tarsalis differed by elevation in Poudre Canyon in 2006 |
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| Abundance of Culex tarsalis females peaked in mid-July in 2006 in the Fort Collins area (below 5,250 ft) but in August at higher elevations in the Poudre Canyon. The period of time with risk of exposure to Culex tarsalis is much shorter at higher elevations than in Front Range cities like Fort Collins. Rapid increases in abundance of Culex tarsalis females appear to occur when mean weekly temperatures consistently exceed 67°F. Note that the early activity in April represents females that have overwintered and are starting to move around as temperatures increase in the spring. |
| Eisen, Bolling and Moore; unpublished data. |
| Emergency spraying to kill adult Culex tarsalis must be initiated in a timely manner. Spraying too late in response to West Nile virus disease cases is not effective because populations of host-seeking female mosquitoes already are in natural rapid declines. High abundance of Culex mosquitoes, or of West Nile virus-infected ones (Vector Index), are better suited as "triggers" for emergency spraying to kill adults than West Nile virus disease cases because they precede human disease cases. |
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| Adapted from Bolling and others 2009. J. Med. Entomol. 46: 1519-1531. |