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Tick-Spread Disease On The Rise In Missouri And Illinois As Midwest Gets Hotter

The lone star tick is an important vector of a number of diseases, including the heartland virus and ehrlichiosis.
Centers for Disease Control and Prevention
The Lone Star tick is one of the most common ticks in Missouri. It carries a number of diseases, including the Bourbon virus. Tick-borne diseases are increasing as Missouri's climate becomes wetter, warmer and more tick-friendly.

The tick season in Missouri is getting longer and more severe, according to researchers in Missouri and Illinois.

Ticks survive best in warm, wet climates. As seasons become warmer due to climate change, more ticks survive, thrive and multiply, latching onto animals and humans and spreading diseases including Lyme disease and Heartland virus, they said.

New tick species also are moving into the central Midwest, carrying new viruses or bacteria with them that can infect humans, pets and livestock.

“Even though we are already seeing these changes …it’s such a slow-progressing thing we don’t feel it right away,” said Ram Raghavan, a University of Missouri epidemiologist who recently completed a three-year field study of ticks in Pittsburg, Kansas, near Joplin.

Raghavan and a former graduate student wanted to paint a comprehensive picture of what kind of ticks were present in the area, how many there were and when they were most active. They ultimately collected and catalogued nearly 16,000 ticks. The findings were published last monthin the scientific journal Plos One.

Following ticks for three years allowed them to determine when people and animals were most at risk of bites. The ticks were active from early March through November, he said.

“The seasons are extending on both sides,” Raghavan said. “You can expect to see ticks active all the way through Thanksgiving on one side, and ticks are becoming active much sooner.”

The study “helps us create a baseline understanding of the current situation from a public health perspective,” he said. “Now we have meaningful, relevant data to look back on for comparisons to see if certain trends continue in the future.”

The data will be helpful at a time when tick-borne diseases are on the rise, both regionally and nationally, Raghavan said. There were more than 50,000 reported cases of tick-related illness in the United States in 2019, according to the Centers for Disease Control and Prevention. That’s more than twice the number reported in 2004.

The researchers found the Lone Star Tick was most common in the Kansas area, where they did their field studies. More than 80% of the ticks they captured were Lone Star ticks.

Lone Star ticks have been steadily making their way north, said Catherine Santanello, a professor of Pharmaceutical Sciences at the University of Southern Illinois-Edwardsville who studies diseases transmitted by bugs.

“It used to be found just in the southeast: Florida, Georgia, etc.,” Santanello said. “If you look up its range, even 40 years ago versus now, it’s much more northerly. Basically that’s in part because the temperature is increasing.”

The Lone Star ticks carry a newly discovered disease: Missourians have beguntesting positive for the Bourbon virus, which causes diarrhea, muscle aches and fever. In some cases, the virus is fatal.

But ticks aren’t the only ones moving. People and animals are beginning to move into previously wild areas, she said. They’re hiking and camping in the woods but also building homes and living in undeveloped areas.

“A lot of it is truly attributed to the fact we’re kind of encroaching on the area of deer, coyotes,” Santanello said. “We’re getting close to them, which causes us to get bitten more.”

She expects other disease-carrying critters, like the Chagas disease-causing Kissing Bug in Central America, to make their way to Missouri in the next few decades.

Follow Sarah on Twitter: @petit_smudge

Correction: A previous version of this story misspelled the name of the Kansas town near where the ticks were collected.

Sarah Fentem is the health reporter at St. Louis Public Radio.