Concern over the presence of West Nile Virus in dead birds and in water samples has prompted the Sacramento-Yolo Mosquito and Vector Control District to consider aerial spraying next week.
Of particular concern for the district is a 25,000-acre patch of North Sacramento County, north of the American River, where many dead birds have tested positive for the West Nile virus and where an inventory of multiple mosquito samples has also tested positive.
To date, 18 dead birds and 58 mosquito samples have tested positive for West Nile virus in the county. One human case has been reported by the California Department of Public Health.
The West Nile activity, while intensifying in Sacramento County, is widespread. In Yolo County 6 dead birds and 19 mosquito samples have also tested positive for West Nile virus. Most of the birds that tested positive are of the American crow species. No humans have tested positive for the virus in Yolo County in 2013.
Last year saw 30 humans and 464 birds test positive for the virus in Sacramento County.
"We're concerned about the high infection rates and are considering aerial spraying" said David Brown, District Manager of the district in a written statement.
No formal decision has been made on the spraying, which would be used to reduce adult mosquito population.
The pesticides typically used for West Nile aerial spraying are pyrethrin or naled.
Typically the pesticide are introduced as an aerial spray at a rate of three quarters of an ounce, or less, per acre.
Although the pesticides used are commonly found in products to treat cats and dogs for fleas and ticks, the district advises individuals to remain indoors and keep windows and doors closed during spraying.
A decision on whether the control district will do the aerial spraying is expected early in the week, and will be dependent on laboratory surveillance results.
If aerial spraying becomes necessary a map of the specific area will be provided.
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Call the Bee's Edward Ortiz, (916) 321-1071. Follow him on Twitter: @edwardortiz