For the last three summers, including this one, Dr. David Claborn has led a team of students who collect mosquitos across Missouri and bring them back to a lab in The Professional Building at Missouri State University.
The university was selected to conduct the study by the Missouri Department of Health and Senior Services. The study’s goal is to see what mosquitos are in the state.
The health department chose MSU because Dr. Claborn is a professor there.
“I am a retired Naval officer, and I was a medical entomologist for the Navy for 20 years. My job was to basically keep Marines from getting malaria and other insect-borne diseases,” said Claborn.
He also has doctorate in public health.
Claborn said there’s never been a large survey to determine what mosquitoes are in Missouri.
“And that is of public health importance because several of these are capable of spreading diseases,” he said.
The need for a statewide survey became more apparent when the Zika virus, which can cause severe birth defects, was found in parts of the U.S. While the study doesn’t look at what viruses are here, it does help health officials determine the risk for viruses by looking at what types of mosquitos exist in Missouri.
So far, Claborn and his team have collected more than 35,000 mosquitos in 36 counties.
Some of the mosquitos are trapped as adults using dry ice as an attractant. The frozen carbon dioxide is similar to what humans breathe out. Others are collected as larvae—in water collected from places like old tires and trunks of junked cars at salvage yards—and the adults emerge in captivity.
“Because if there is a risk of Zika transmission, it’s going to be from mosquitos that develop in artificial containers,” Claborn said.
The researchers kill the adult mosquitos by freezing them. Once they’re identified, the best specimens are pinned, labeled and placed in cases. When the study is complete, they’ll go to an insect museum—perhaps at the University of Missouri or the University of Arkansas.
Because some mosquitos are difficult to identify with the naked eye, researchers put a spot of glue on the end of a wooden stick, touch it to the mosquito so it adheres and then look at the specimen under a microscope.
The study has identified 40 species of mosquitoes in Missouri so far.
The researchers were particularly interested to see if the most likely carrier of Zika, the Aedes aegypti, is here. So far, they haven’t found it.
“We can't say for sure that the mosquito does not occur in Missouri, but if it does occur, it’s hiding pretty well,” Claborn said.
They have, however, found another invasive species that was introduced into the U.S. from Japan about 30 years ago. It was already known that the Asian tiger mosquito was in the state, but the MSU survey determined that it’s very common. It was found in every county where mosquitos were collected, and Claborn says it’s quite capable of transmitting Zika as well.
“The good news is that the really efficient vector is either not here or is in very low numbers. But the bad news is that another vector is here in very large numbers, and it’s everywhere,” Claborn said.
Another invasive species the team identified is the Aedes Japonicus, which had only been identified in one place in Missouri—the St. Louis area. They found it during the study in large numbers in about half the counties that were sampled. It’s not yet known what the risk associated with that mosquito is.
Claborn pointed to a mosquito that was the primary vector of malaria when it was common in the U.S. and Missouri in the early part of the 20th century—the anopheles genus.
“If we reimported malaria here and allowed it to become established, this mosquito would still be quite capable of transmitting it, and it occurs in very, very large numbers in certain places. Fortunately, we don’t have the disease actively transmitted in the country anymore,” Claborn said.
What you might not know about mosquitos—only the females bite. Males feed on plant juices, and females do, too, according to Claborn. But they take blood meals as a protein source to make eggs.
While mosquitos can transmit diseases to humans, they serve a valuable purpose to the ecology of Missouri, and eradicating them would do much more harm than good. But Claborn said there are ways to reduce human disease risk such as eliminating standing water in artificial containers and using insecticides when there’s a disease transmission risk.
This is the last summer for the study by Missouri State University. Once it’s complete, the data will be sent to the Centers for Disease Control and Prevention.