Case studies in New York and in Florida have shown that after many years of spraying adult mosquitoes to control Equine Encephalitis, populations of the targeted disease-carrying mosquito have actually increased. Controlling mosquitoes at the larval stage using relatively non-toxic and selective microbes and insect growth hormone regulators remains the most effective and least environmentally harmful methodology available. Larvaciding of mosquitoes is the primary prevention strategy recommended by the U.S. Centers for Disease Control and Prevention for St. Louis Encephalitis and West Nile Virus. Pyrethroids, widely touted by government and mosquito control officials as harmless to humans and terrestrial wildlife, are suspected endocrine disruptors, and have also been shown to alter chromosomes in human white blood cells. In laboratory studies, many of the organophosphate insecticides can cause neurological disorders, immune dysfunction in children, and cancer in laboratory animals.
Birds are important sentinels for the overall health of the environment.
Birds dying from West Nile Virus originally alerted public health officials in the United States to the presence of the virus. Experts agree that the practice of adulticiding for mosquito control in urban and suburban locales will not eradicate the West Nile Virus from wild populations of animal reservoirs and, in the vast majority of cases where insecticides have been sprayed in the recent past, is unwarranted for the protection of humans from the virus. Using these guidelines in nearly all instances, adulticiding should not be undertaken as a mosquito control measure. Localized use of registered larvacides should continue in attempt to control populations of mosquitoes likely to come into contact with infected West Nile animal reservoirs and humans. Larvaciding should only be undertaken in disturbed or man-made bodies of water, which are of lesser ecological importance.