After the large amounts of rainfall the past few months and the resulting standing water in Battle Mountain, residents should be cautious about mosquitoes, in particular a dominant species called Culex tarsalis, which can carry the West Nile virus.
Entomologist Robin Gray of Seven Valleys LLC is on contract to Lander County, and she has been working diligently on the mosquito abatement in the Battle Mountain area.
Gray stated she did a river treatment and a big adulticide spray by air on June 4. Adulticide sprays immediately kill flying mosquitoes. “We sprayed almost 10,000 acres. That kind of thing is going to continue, and I don’t think we’re anywhere near done with aerial sprays, because there’s a lot of water out there. Until the river goes down, the water is going to persist, and there’s going to be a big build-up of Culex tarsalis,” she stated.
“The mosquitoes that are coming on now are Culex tarsalis, a vector of West Nile virus. They’re going to have a lot of habitat, so we aren’t going to be done aerial spraying for quite a while. We’ll still be doing larviciding every week right up to the end of mosquito season.” Gray said she tries to focus on killing mosquito larvae, because then they don’t come out as adults and cause a problem. “But now with the situation where there’s just thousands upon thousands of acres of flooded ground, even if we larvicided a good amount of that, they’re still flying in from elsewhere, so we’re coping with that by adulticiding.”
Gray started testing all the adult Culex tarsalis she catches for West Nile virus. “It’s been in Battle Mountain and Winnemucca, and all the little towns in Northern Nevada at one point or another.”
Asked if one could tell if they have the virus once bitten by a mosquito, felt sick and went to a doctor, she said she has her doubts. “When West Nile first hit Nevada, it was everywhere, and I was getting bit by Culex tarsalis a lot at night. I tested them for West Nile virus and they were positive for it. I felt some extreme fatigue and went in and had myself tested, and it came back negative. How could I get bit dozens and dozens of times and not get it? Recently I talked about this at a mosquito conference and they said it’s possible that they didn’t test me at the right time; the test wouldn’t pick up the antibodies. So, I have a feeling that I’ve had it but it didn’t really develop into the full-blown disease. I can’t prove that but I suspect it.” Gray pointed out, “You could build up a resistance to it, once you’ve had it, but a person could get seriously ill. With Culex tarsalis, people need to take some precautions, wear long sleeves. They are most active at night and they will come into the house, through open doors and screenless windows. Culex tarsalis aren’t going to look different than other mosquitoes unless you’ve been working with them and can identify them.”
“They’re out there at night and not really daytime biters,” she said. “We’ll be spraying again and try and cut the populations down but people need to realize that even spraying under good conditions does not get 100% of the mosquitoes, and it’s unrealistic to think it’s going to.”
Precautions should be taken regarding standing water around living spaces, because Culex tarsalis will breed in containers like birdbaths and flower pots. The best defense is to use a good repellent, and wear long sleeves and pants if going out at night. Gray said there’s a tendency that they are more attracted to dark clothes.
Culex tarsalis is the chief vector of western equine encephalitis virus. Gray said there is a vaccination for horses but unfortunately none for people.
“They carry other viruses, including malaria, but West Nile virus is the big one,” warned Gray. “Every year this particular species [Culex tarsalis] becomes the dominant mosquito around here. The other ones everyone is griping about, they’re associated with flooding, and once the flooding has happened not many new ones come out; instead it shifts over to other mosquitoes and Culex tarsalis is the big one – everywhere we’re working, it’s becoming the dominant mosquito. They’re not the only ones but in a few weeks, there will be 10 times more of them than all the other mosquitoes combined.”
If bitten, there is symptomatic relief available but no vaccine.