Lone Star tick brings Heartland virus to Southern Illinois

News-DemocratJuly 23, 2013 

Yes, there are more ticks out there this year, but pinning down an exact reason for the bump in population is difficult.

"My take on it would be: It's often hard to say with any certainty what causes variation in the population of any species of arthropod," said Dr. Brian Allan, an entomologist with the Department of Entomology at the University of Illinois at Urbana-Champaign.

Allan specializes in the study of ticks and mosquitoes.

"Ticks have a multi-year life cycle so they live through several years and several life stages. It's hard to say with certainty the reason we have more ticks is because we had a warm summer, or because of something else that played a role. It could have been that an important host animal had a good year or that we had a mild winter. There could be multiple explanations."

There are several species of ticks that call Illinois home, and insect scientists have seen a rise in the American dog tick this year, a species known to play host to Rocky Mountain spotted fever.

Another species of tick, the Lone Star tick, also carries the disease and was recently discovered to carry a rare virus: The Heartland virus. The virus had not been found in ticks previously. The Lone Star tick calls Southern Illinois home and is also known to carry Rocky Mountain spotted fever and ehrlichiosis.

"People living in the southern half of Illinois should be more concerned than those who don't, but, the Lone Star tick is not a major carrier of the virus," Allan said. "I think it's something certainly to be aware of, but no special or additional precautions are needed. Ticks can transmit diseases, and there are steps you can take to protect yourself if you like to recreate outside."

Heartland virus was diagnosed in two people in Missouri in 2009. Researchers collected nearly 60,000 ticks and found the virus in one out of every 500 Lone Star ticks tested, according to a report about the virus published Monday by the Centers for Disease Control and Prevention. The virus causes low white blood cell counts, fever, headaches, chills and mild diarrhea. Both people infected with the virus recovered. Because it is a virus, Heartland is not treatable with antibiotics.

Melaney Arnold with the Illinois Department of Public Health confirmed there have been no diagnosed cases of the virus in Illinois.

"There are a lot of tick-borne illnesses and our recommendations are the same: Wear a repellent with 20-30 percent DEET, a product that contains permethrin, tuck pants into boots, avoid high grass, and do tick checks after you go out walking in the woods," Arnold said.

The bite of an infected tick can transmit Lyme disease, Rocky Mountain spotted fever, tularemia, ehrlichiosis, and now, Heartland virus. It takes at least 24 hours for a disease to transfer from tick to human, so, the faster a tick is found and removed and attachment prevented, the less likely any disease will be transmitted.

Ticks aren't the only blood-sucking insect that seem to have increased numbers this year.

Mosquitos also have had a good year, but, not the particular species that carries West Nile Virus, Allan said. In fact, it's been a worse year for the Culex, or common house mosquito, than last year because of the wet spring and early summer

"Which seems counter-intuitive," he said. "Last summer was a very bad summer because it was a very dry summer. There were more incidents of mosquito-borne disease, like West Nile virus, because of the drought."

Mosquitos need water to breed so how can a drought create more disease-carrying mosquitos?

The answer: Catch basins in urban and downtown areas that are designed to hold excess run-off.

"Those species tend to live in urban/downtown areas and the reason you get more of those during a dry year than a wet year is because the larvae get washed out of the catch basins during a wet year, more than they do during a dry year," he said. "When they don't get washed out, there are more mosquitoes. Last summer was one of the worst summers for West Nile virus because it was such a dry year."

But, that doesn't mean mosquitoes are having a bad breeding year. There is a species that thrives in the water and is usually the mosquito that invades backyard parties.

"The mosquitoes that like to breed in flood waters are probably more numerous this year," Allan said. "People are probably getting bitten by lots of mosquitoes, and, because of that, they think they are having a really bad mosquito year, especially in rural areas. Fortunately, flood water mosquitoes tend not to be important disease vectors in the U.S. People could be sitting in their backyards getting bit to pieces, but, they are probably not getting bitten by one of the species that carries diseases."

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