Sedgwick County prediction: Rainy May, more mosquitoes

A female Aedes aegypti mosquito in the process of acquiring a blood meal from her human host.
A female Aedes aegypti mosquito in the process of acquiring a blood meal from her human host. Courtesy of CDC

It’s a mosquito’s favorite time of year.

With 11.77 inches of rain recorded in May, health officials in Sedgwick County are predicting increased numbers of mosquitoes, including the genus of species that carry West Nile virus: the Culex mosquitoes.

Because of the recent rainfall, Sedgwick County Health Department Director Adrienne Byrne-Lutz is encouraging people to steer clear of standing water, or better yet, get rid of it.

Mosquitoes “like stagnant water, like tires, birdbaths; anything standing has got to be drained,” Byrne-Lutz said.

That’s because standing water is a breeding ground for the insects, she said.

Mosquitoes 101

Female mosquitoes require a “blood meal” in order to lay eggs, said Raymond Cloyd, professor of entomology at Kansas State University. The females use sucking mouth parts to consume the blood of humans, dogs, horses, reptiles or birds.

Meanwhile, the males consume moisture from plants and leaves. A mosquito will typically live about two weeks, Cloyd said.

Mosquitoes breed on standing water, and the females lay 30 to 50 eggs – depending on the species – on “rafts” in the water.

“The eggs become wrigglers and sink to the bottom or come to the surface” of the water, Cloyd said. “Then they pupate, the transitional stage between larvae and adult.”

From there, the life cycle beings all over again.

West Nile, chikungunya viruses

Mosquitoes get infected with West Nile virus when they feed on infected birds. They then transfer the virus through biting their host.

About 80 percent of people infected with West Nile do not show any symptoms, according to the county health department. Noticeable symptoms include fever, headache, body ache, nausea and vomiting, while severe symptoms include high fever, tremors, vision loss, paralysis and coma.

West Nile cases seem to be dropping in Sedgwick County. There was only one case in 2014 after 11 cases in 2013 and 21 in 2012, according to numbers from the health department.

So far, there haven’t been any cases of West Nile virus this year in Sedgwick County.

In the past two years, there has been an outbreak in Florida of chikungunya, a virus also spread via mosquito bite. It causes symptoms such as fever, joint pain, headache and rash, according to the Centers for Disease Control and Prevention. Previously, chikungunya had been found in Asia, Africa, Europe and areas in the Pacific and Indian oceans, but not the United States.

“The problem is that it’s a new virus,” said Ingrid Garrison, public health veterinarian with the Kansas Department of Health and Environment. “Anytime you get a new virus where people have never seen a disease before, you’re going to get an outbreak.”

But that hasn’t been the case in Kansas, where the mosquitoes that carry chikungunya can’t survive the non-tropical conditions, Garrison said.

There were 13 cases of chikungunya in Kansas last year, KDHE spokeswoman Sara Belfry said, but each of them were travel-related, in which the infected people had returned from a tropical area already showing chikungunya symptoms.

Preventing West Nile

The decrease in cases of West Nile virus in Sedgwick County, Byrne-Lutz said, could be because of the county’s efforts to spread awareness about bite prevention and targeted mosquito control efforts.

During the summer months, the county – in a partnership with KDHE – weekly monitors nine mosquito traps near bodies of water in undisclosed, public locations across Sedgwick County. Entomologists then take the trapped insects to the lab to count the species and test for viruses.

The data goes back to the county, and if there are a certain number of Culex mosquitoes – the genus that includes species able to carry West Nile – collected in one area, then the health department and city of Wichita will treat the body of water with larvicides that target the eggs of mosquitoes.

“It’s really important to monitor West Nile virus in the community because even though the majority of people will have very mild symptoms, there are 15 to 20 percent of people that can have very serious effects, especially for those with compromised immune systems,” such as newborns and the elderly, Byrne-Lutz said.

Although nearly 50 species of mosquitoes exist in Kansas, Christopher Rogers, an ecologist with the Kansas Biological Survey at the University of Kansas, will find just 10 to 18 species per trap during the course of the summer in Sedgwick County, Rogers said. Not all species of mosquitoes bite humans.

Preventing bites

To protect yourself from mosquito bites and the risk for West Nile, Bryne-Lutz said, you should:

▪ Drain standing water.

▪ Dress in long sleeves and pants, especially at dusk and dawn.

▪ Use insect repellents containing the key ingredient deet.

There are a number of home remedies promising to rid of summertime pests, such as citronella candles, dryer sheets, Listerine and catnip.

Consumer Reports’ July issue explained that candles and diffusers don’t do the job of keeping mosquitoes at bay, but that an oscillating fan may do the trick. Otherwise, stick with repellents with 20 percent picaridin and 30 percent oil of lemon eucalyptus for a natural, safer option, but repellents with concentrations of less than 30 percent deet are safe for use.

The idea that some people are more attractive to mosquitoes than others may be true, said Cloyd, the K-State professor. Women who wear perfume and other fragrances, and people who tend to sweat more profusely, are more likely to be bitten, he said.

Other home remedies, like using marigold flowers and garlic to ward off the hungry insects, are not supported by data, Cloyd said.

For now, the health department is certain that eliminating standing water – along with using protective measures like dress and repellents – will help in preventing mosquito bites.

“It’s crucial that we monitor this and do a lot of educating on prevention,” Bryne-Lutz said, “so people can see how they can affect the spread of West Nile.”

Reach Shelby Reynolds at 316-268-6514 or sreynolds@wichitaeagle.com. Follow her on Twitter: @_shelbyreynolds.

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