Mosquito population expected to be very high to severe in Iowa soon

OFF!Cast, OFF!’s mosquito forecasting tool, indicates that the mosquito population in central Iowa is growing.

The OFF!Cast map, which predicts local mosquito populations up to seven days in advance, predicts a high to very high mosquito population on Friday and Saturday, which will become severe on Sunday and last the rest of the week.

The influx of mosquitoes in the state comes just a week before World Mosquito Day on August 20, a day that recognizes the discovery in 1897 that Anopheles mosquitoes transmit the malaria parasite to humans; this year marks the 125th anniversary.

Dr. Ryan Smith, an associate professor in the Department of Entomology at Iowa State University, previously told the Des Moines Register that higher mosquito populations were expected this year due to warmer temperatures and increased precipitation.

Smith oversees the university’s mosquito surveillance program, Smith Laboratory, which monitors mosquito populations and mosquito-borne diseases in Iowa.

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The department does not forecast mosquito populations, but partners with agencies such as the Iowa Department of Public Health and the State Hygienic Lab at the University of Iowa, to analyze trends in real time. . Data from the university this year already showed a spike in mosquito populations in early June, before plunging again, Smith told the register.

Despite early predictions of an above-average summer for mosquitoes, drought conditions in the state have reduced the mosquito population since June, he said.

“What I can say is that we’re not seeing a lot of mosquitoes right now,” Smith said. “I would probably say it’s a little less than normal.”

According to Smith, recent lab observations do not support the prediction of OFF! that there will be an increase in the mosquito population next week.

“At least some of our major nuisance mosquitoes, they really haven’t been in huge numbers for the past two weeks, so I don’t think there’s a huge risk per se of it being ‘serious’,” Smith says. . “I’m not going to say that there aren’t mosquitoes there. And there is, as we go further into the summer, an increased risk of West Nile virus in your mosquito population. . But I think quite comfortably, you can’t worry about a big swarm of mosquitoes.”

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Despite August being World Mosquito Day, Smith says the mosquito population typically hits a low point during that month.

A mosquito dines on a human.

“This August time is usually the lowest in the summer,” Smith said. “I would say historically we usually see a lot of mosquitoes in early May and June. And then we tend to see an increase later on, once you get into September. But right now it’s very dry, and there’s just not a lot of activity that we’re seeing right now.”

Mosquito populations in Iowa, he said, vary from year to year, but generally spike from May through October. Iowa has about 57 species of mosquitoes, according to Smith. The lab selects a handful of counties across the state each year to observe mosquito populations.

In 2022, the lab observed and collected samples of more than 67,000 mosquitoes in seven counties: Polk, Story, O’Brien, Page, Woodburn, Blackhawk and Johnson, according to this year’s mosquito surveillance data from the university.

The vast majority of those observed — 60,081 — were in Polk County, according to university surveillance data. And about 95% of the mosquitoes observed in all monitoring locations were aedes vexansa common mosquito that does not transmit disease.

The laboratory closely monitors Culex species of mosquitoes, which like to feed on birds, including blue jays and crows; mosquitoes often carry the virus and then bite humans, infecting them.

Mosquito surveillance by Iowa State University in 2016 found that neither of the two species most associated with Zika virus were found in Iowa, but West Nile virus appeared more frequently than there is. two years.

Although mosquitoes tend to be more numerous in early summer, the types most likely to carry West Nile virus tend to come out in late summer and early fall, as the Des Moines Register has already reported.

“So even though there aren’t a lot of mosquitoes right now, it’s still the time of year when West Nile virus is usually ramping up,” Smith said. . “As we come into late August and early September, that’s usually when the bulk of our West Nile virus transmission occurs.”

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The virus, which can cause dangerous fevers and brain swelling, arrived in Iowa in 2001 and peaked here in 2003, when it caused 147 confirmed illnesses and killed six Iowans. The next spike was in 2018 when the virus seriously sickened 73 Iowans and killed three. Cases in the state have been in the single digits in the years since.

“West Nile virus is transmitted by Culex mosquitoes and these are most active in the evening at dusk, so if you are going to be outside during these times I will definitely try to wear repellent,” said Smith. “Most of the time, people infected with West Nile virus will be rejected. But in reality, it requires hospitalization and can lead to death. It’s a pretty serious virus that I wouldn’t wish on people.”

Iowans should follow precautions and drain any standing water near their homes to avoid a breeding ground for mosquitoes that could potentially carry the virus, Smith said.

The mosquito forecasting tool from OFF!  predicts very high to severe mosquito populations in Iowa next week, ahead of World Mosquito Day on August 20.

Protect yourself from mosquito bites

The Iowa Department of Public Health has these tips for Iowans to protect themselves from insect bites:

  • Use an insect repellent containing DEET, picaridin, lemon eucalyptus oil, or IR3535. Always read the repellent label and consult a health care provider if you have any questions about using these types of products for children. For example, lemon eucalyptus oil should not be used on children under 3 years old and DEET should not be used on babies under 2 months old.
  • Avoid outdoor activities at dusk and dawn, when mosquitoes are most active.
  • Wear long-sleeved shirts, pants, shoes, and socks outside.
  • Eliminate standing water around your property, as this is where mosquitoes lay their eggs. Empty water from buckets, canisters, pool covers and pet water dishes. Change birdbath water every three to four days.

The city of Des Moines contracts with Clarke, an Illinois-based mosquito control company, to manage the bugs. Services include standing water inspections and testing, as well as larval and adult control, according to the city’s website.

Malaria is transmitted by mosquito bites and kills a child every two minutes.

Des Moines residents can call the Mosquito Hotline using the Clarke Customer Portal or at 800-942-2555 to report standing water concerns, request a neighborhood spray, or be added to the list of spray stop. For more information, visit dsm.city/departments/neighborhood_services/mosquito_control.php

Residents with questions about the city’s mosquito control program or product information can call Chris Heilskov at 515-237-1486 or Vince Travis at 515-283-4077 between 7:30 a.m. and 4 p.m., Monday through Friday. .

Grace Altenhofen is a reporter for the Des Moines Register. She can be reached at [email protected] or on Twitter @gracealtenhofen.