The Centers for Disease Control and Prevention recently awarded Kansas more than $350,000 to support efforts to protect Kansans from Zika virus, a mosquito-borne disease. The money also will go toward eliminating adverse health outcomes that can result from Zika infection, including severe birth defects.
Now, state agencies are working to identify and monitor the two species of mosquito that transmit the Zika virus.
Mosquito season went into full swing when early rains and warm temperatures started the population with a bang this spring. But with rising concerns of Zika virus in the United States, the itchy welts that come from mosquito bites are no longer just annoying. They’re scary.
In an effort to lessen fears and keep track of the prevalence of the tiny flying bugs, the Kansas Department of Health and Environment, along with specialists from the University of Kansas, conduct mosquito surveillance each year. Researchers trap and count the insects and identify them by species.
Christopher Rogers, with the Kansas Biological Survey, is one of the researchers tasked with mosquito monitoring in Kansas.
Just off the sidewalk at Chisholm Creek Park in Wichita near the Great Plains Nature Center, Rogers stands next to an interesting contraption. It looks a little like black paint bucket with a long, skinny bird feeder hanging from it. And while seemingly simple, this mosquito trap is a key piece of the puzzle for Kansans hoping to avoid mosquito-borne illnesses.
Of the 50 species of mosquitoes in the state, Rogers said only about half bite.
“And of those species that do bite, only the female bites, and she only bites when she needs to lay eggs," he said.
In order to find someone or something to bite, the female mosquitoes look for our breath — or, more specifically, the carbon dioxide that we breathe out. Rogers’ trap simulates that using a bucket filled with dry ice, which puts off the gas as it melts.
The hanging contraption also has a small light near the top, which serves the same purpose that a lighthouse does for ships at sea. As the mosquitoes fly toward the carbon dioxide, they see the light and think it’s body heat. That’s how they identify their next meal, which, thankfully, this time, is not a person.
“They fly in,” Rogers said, pointing at the trap. “And inside of here is a fan, which sucks the mosquitoes down into the sleeve cage.”
The sleeve cage is exactly what it sounds like: a sheath of tightly woven netting that traps the mosquitoes. Rogers said it can hold anywhere from a few dozen to 7,000 mosquitoes, which he then puts on dry ice to knock them out so he can get to work identifying the insects down to a species level.
He says different varieties are distinguishable by the arrangement of veins in their fragile wings or the patterns found in scales, spines and hairs on their tiny bodies. The species he’s looking for are varieties of the Aedes mosquito: Aedes aegypti, which is native to Africa, and Aedes albopictus, which comes from Asia.
“These are the two that we’re most concerned about because they have the potential to carry the Zika virus,” Rogers said. “These are the two species that are carrying Zika virus in Central and South America, Puerto Rico, the Caribbean and whatnot.”
If either Aedes variety is found in one of Rogers’ traps, its body is sent to a KDHE laboratory.
“We look for the DNA of the virus in the mosquitoes. That way we can tell if the mosquitoes are actually transmitting the disease,” he said.
Eight cases in Kansas
The state of Kansas has been doing this kind of work — trapping, counting and identifying mosquitoes — for years in order to keep tabs on other mosquito-borne diseases like West Nile virus, which first showed up in the state in 2002. Rogers’ work helps state agencies like the KDHE determine where certain species of the insect are found and how dense the population is.
“By knowing what species of mosquitoes are coming into the traps, we can direct Sedgwick County in their efforts to control the mosquito larvae, and they know where to go look for habitat where the larvae may be coming from,” he said.
So, that begs the question everyone seems to be asking: Is it just a matter of time before Zika virus does show up in Kansas?
“Zika virus has shown up in Kansas in people who went to other places, got the virus and came here,” Rogers said. “Because there are people here who have Zika — and there’s very few — these mosquitoes, all they have to do is go and bite that person and now they’ve got the virus. So far, these people are doing everything in their power not to get bitten by these mosquitoes.”
Eight cases of Zika have been confirmed in Kansas, and none of those originated in the United States. In fact, according to the KDHE, there have been no local transmissions of the virus in the continental United States.
Rogers said the countries that have been inundated with cases of Zika virus tend to be tropical places where mosquitoes are out year-round. One thing in Kansas’ favor is the colder winter weather.
“As soon as winter comes, they’re all dead,” he said. “All that’s left behind is their eggs. Now, as far as we know, so far all the data shows that the mosquitoes are not passing the virus to their eggs.”
So that’s a good thing. But, Rogers said, next year, it will start over again.
“If Zika virus does show up in the mosquitoes in Kansas, it’s going to reset every single year,” he said. “And it’s probably not going to be as huge a problem as we’re seeing in more tropical areas. We don’t know. We honestly don’t know what we’re up against yet.”
“As soon as winter comes, they’re all dead. All that’s left behind is their eggs.”- Christopher Rogers, with the Kansas Biological Survey
But there are ways to reduce the chances of getting Zika virus, like using DEET, staying covered and avoiding places where mosquitoes are likely to be in large numbers, and especially where they breed.
Rogers said that doesn’t only mean roadside ditches and stagnant ponds. The species of mosquito that can carry Zika, Aedes aegypti and Aedes albopictus, actually nest in trees with rotten hollows or pockets between limbs that can hold water.
Aedes aegypti has mainly been found along the Kansas-Missouri border and as far west of that as Topeka, he said. Aedes albopictus has been found in Sedgwick County for quite some time. But according to the KDHE, the precise range of both species is unknown, and just because the mosquitoes are here, that doesn’t mean they’re transmitting Zika to Kansans.
“I’m running traps all across the state to figure out where it lives, why it’s there, how did it get there,” Rogers said.
And with that data, the KDHE should be able to assess potential threat levels should Zika virus ever show up in mosquitoes in Kansas.
— Abigail Wilson is a reporter for KMUW.