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Study: Up to 80 percent of county mosquitoes carry West Nile virus

Nov 13, 2012 - By Katie Roenigk, Staff Writer

Students at Central Wyoming College determined that up to 80 percent of Fremont County's mosquito population this summer was made up of bugs that carry West Nile virus.

Biology professor Steve McAllister said the numbers are higher than in the past, when 20 to 30 percent of mosquitoes were of the Culex tarsalis variety that can transmit West Nile to humans.

"No one really knows why we have these outbreaks," he said last month during a CWC Board of Trustees meeting.

He guessed the increase in Culex tarsalis could be connected to drought conditions, which occurred in areas of Texas where West Nile was prevalent this year.

"Those conditions seemed to set up a large mosquito population in the new year," McAllister said. "We just had a drought this summer, so we're very interested to see what happens next year."

He said his students are excited about the research, which is funded through the Idea Networks for Biomedical Research Excellence program that has worked to build Wyoming's biomedical research and education infrastructure since 2002.

This is McAllister's third year undertaking West Nile research with CWC students through the INBRE program. His classes spend warmer months collecting mosquitoes and checking the bugs for West Nile, while in the fall and winter students analyze blood samples that come from local residents.

They received dozens of blood samples last week during a health fair for state employees at CWC, and McAllister said he plans to contact area hospitals and other institutions that may be willing to collect blood for West Nile research.

"We're looking at past exposure (to West Nile)," McAllister said. "When you've had WNV you retain antibodies to the virus in your blood. So we test for two kinds of antibodies."

He explained that one antibody remains in an infected person's blood for the rest of his or her life.

"That helps prevent you from getting the disease again," McAllister said.

The other antibody is less common and only appears when a person is infected with West Nile at the time that his or her blood is drawn. If that antibody is detected in a blood sample, McAllister said he will notify the blood donor.

"Otherwise we don't disclose the results to individual people," he said, advising residents to visit their physician if they want to know whether they have contracted West Nile in the past.

"We're not a clinical lab," McAllister said. "We're research. We don't want to give someone a false sense of security by telling them they're immune."

He said past results indicate that roughly 20 percent of Fremont County residents have been infected with the virus.

"It's a fairly high percentage actually," McAllister said. "It does indicate, though, that most people still are at risk. That's kind of the message we want to get out."