Ryan Smith. (ISU photo)
The one good thing about the Iowa weather this time of year is you don’t have to worry about mosquitoes.
Information just released by Iowa State University’s mosquito surveillance program found mosquito activity was particularly high this year. ISU entomologist Ryan Smith says one thing they didn’t find in trapping nearly 176,000 mosquitoes were any concerns about the Zika virus.
“At least in our trapping, we don’t appear to have found any of these established populations of these Zika-carrying mosquitoes here in Iowa,” Smith says. The two types of mosquitoes that carry Zika have been found in Missouri and Illinois, and ISU did some more trapping in southern Iowa this year.
“Going into it we weren’t real sure what we would find,” Smith says. I think at least so far what the data would suggest is that they really haven’t established themselves here in the state.”
The bigger concern is that the ISU Medical Entomology Lab collected 46 “pools” of mosquitoes that tested positive for West Nile virus in 2016, an increase from the 17 pools that tested positive in 2015.
“West Nile has been here for about 15 years and it still is around — and even though it may not be grabbing the media attention, it is still is very important,” according to Smith. “We had I believe 44 human cases this last year and even one death. So, it still should be very much on the radar map of everyone in the state.”
Smith says the weather conditions were part of the increase in West Nile mosquitoes. He says they found that having a drought condition and having warmth during the summer tends to result in more West Nile Virus cases. “This isn’t a perfect estimation, but it is at least a pretty good one.”
Smith says having rain isn’t that important for the West Nile variety of mosquitoes to survive. “Some of the other mosquitoes that we have in the state, they do lye dormant, and then when they do experience a strong rainfall they kind of pop out and then the populations explode,” Smith says. “But the culex populations that transmit West Nile are a little bit more stable, a little bit more kind of the same throughout the year. Where some of these other mosquito populations will kind of rise and fall depending on the rainfall.”
Smith says the ISU surveillance found that overall mosquito activity peaked unusually early in 2016 as populations reached their highest levels in late May, likely due to wet conditions in April.
Back to the mosquitoes that carry Zika — he says they continue to move. “It is creeping northward and I think it is probably only a matter of time before it finds its way here in the state,” Smith says. But, he says even if those mosquitoes make it here, that doesn’t mean they would pose an immediate Zika threat.
“Just because they are here doesn’t mean that they are going to spread a disease. You kind of need a reservoir or pool for that specific virus to kind of go ahead to take shape,” Smith explains. “At least this last year with Zika, I think that reservoir only really kind of took place in someplace like Florida.”
Smith says people in Iowa are better off worrying about West Nile and taking steps to keep from being bitten when the mosquito season rolls back around again in the spring.
The final report on the laboratory’s 2016 mosquito surveillance is available here.