West Nile still not detected, but could be in the coming months

The Humboldt County Commission got the buzz from the county’s contract entomologist Robin Gray regarding this year’s mosquito situation. As is to be expected with such a wet year, Gray said the mosquito population had increased over years when the county experienced drier conditions. 

“There's been a lot of flooding along the Humboldt flood plain this year,” she said.  “The Quinn River overflowed its banks and that always means there's going to be mosquitoes in Orovada more than usual.” Gray said there had been a fair amount of flooding in McDermitt and Golconda as well.

Gray said the County conducts the mosquito abatement program using a variety of methods including aerial spraying, fogging and stocking certain waterways with the Gambusia, also known as the mosquito fish. “We use mosquito fish in Golconda and Winnemucca [and] we raise them ourselves in a pond in Paradise Valley,” she said. Gray estimated that she and her crew stocked waterways with approximately 80,000 fish this year. “They're good against some mosquitos not so good against others,” she said.

Gray told the Commission she also tests for the West Nile virus in the 20 to 25 trap locations throughout the county, which she began testing for in June. “Since Culex is the vector of West Nile virus,” she says, “we want to keep a pretty close watch on that. If we find any positive mosquitoes for West Nile [virus], we're going to go in and fog that place until we don't find any more positive mosquitoes.” 

So far, she says no mosquitoes have tested positive for the virus, but it could still happen this year. “We're coming up on the time of year when you generally start seeing West Nile, if we're going to see it at all,” she said, adding that usually August and September are the big months for the virus to show up in mosquitoes.

According to the Centers for Disease Control (CDC), the West Nile virus is the leading cause of mosquito-borne disease in the United States. There are no vaccines to prevent or medications to treat the virus in people. The CDC reports that Nevada has had one confirmed case of West Nile as of July 23. 

Gray said she will continue to monitor the mosquito population and apply the necessary treatments as needed. She said she intends to do at least one more aerial spray application in Winnemucca but wants to wait until water within the Humboldt River flood plain has diminished. The Culex and the Anopheles mosquitoes can quickly recover after an abatement treatment because of its life cycle. “Floodwater mosquitoes usually have a single batch of mosquitoes,” she said. When floodwaters come in these species have a mass hatch and by spraying at the right time, the population can be almost completely eradicated, Gray said. “But these other mosquitoes don't do that. Culex and Anopheles lay eggs and there's just a continuous production of them. When we go out and spray, especially when there's a lot of water around and we've got a big population, they can just bounce back right away,” she said.