The Washoe County Health District Vector-Borne Disease Prevention Program will started its third scheduled mosquito abatement operation Thursday. Helicopter applications of larvacides and insect fogging will be applied to 850 acres of wetlands in Lemmon Valley, Red Hawk, Rosewood Lakes, Butler Ranch, South Meadows, Damonte Ranch and Washoe Valley. So far no local mosquitoes have tested positive for Zika, West Nile virus, Western equine encephalitis or St. Louis encephalitis.