The Town currently sprays for adult mosquitoes only when a positive mosquito sample from an area is tested and shown to be positive for the West Nile virus. If this occurs, the Town would then have a licensed mosquito contractor spray the immediate area, approximately 1/2 square mile, surrounding where the mosquitoes were found to be positive for the West Nile virus.
If the Town receives confirmation from the Denton County Health Department Epidemiologist that a cluster of persons (multiple unrelated within a specific radius) have been positively diagnosed with West Nile virus, the Town would then have a licensed mosquito contractor spray the immediate area, approximately 1/2 square mile, surrounding the cluster field. For ground spraying events, the Town currently follows the CDC recommended spraying guidelines. The CDC recommends ground spraying to occur for 3 consecutive nights within the designated spray area.
In the event of notification of a single human case of West Nile infection, the Town does not conduct spraying activities immediately. The Town increases trapping in the surrounding area. Normal procedures for testing and spraying are followed.
The Town does not spray routinely for nuisance mosquitoes. Spraying occurs only due to the identification of the presence of West Nile virus and is limited to the immediate 1/2 square mile area and is done so to aid in the reduction of mosquito borne infection in humans. Research has shown that spraying for adult mosquitoes is only about 2-3% effective, in that the spray must actually contact mosquitoes in order to kill them because there is no residual effect.
A much more effective means of controlling the mosquito population is to reduce the source and number of breeding areas. By eliminating areas of standing water and treating areas of standing water that cannot be eliminated with an effective, environmentally safe, mosquito larvicide, mosquito larvae can be reduced or eliminated. Only about 1% of mosquitoes are actually infected with the West Nile Virus, and only about 2% of the individuals that are bitten by an infected mosquito actually develop the symptoms of West Nile virus.