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An Asian tick is spreading across Missouri and threatening cattle herds

Longhorned ticks, shown here on a dime to indicate scale, are spreading across Missouri.
University of Missouri
Longhorned ticks, shown on a dime to indicate scale, are spreading across Missouri.

An invasive tick that can do severe damage to commercial cattle herds is showing up in new places across Missouri.

Researchers at the University of Missouri’s College of Veterinary Medicine have found longhorned ticks in Boone County, the first confirmed sighting of the member of the arachnid class in central Missouri.

“We know that this tick is very adaptable and capable of spreading to new areas quickly,” said Rosalie Ierardi, a clinical instructor and doctoral student at the university who made the discovery in April. “And it's very likely that this tick is in other places as well, and it just hasn't been found or recognized in those areas yet.”

The tick native to Asia was first found in Missouri in 2021 and has been spreading ever since. It can carry theileriosis, a disease that kills red blood cells in cattle, leaving them anemic.

“Just like people with anemia, [cattle] don't have enough oxygen-carrying capacity in the blood. So they get really tired. They don't eat well, they can lose their pregnancies, lose weight, they can die from this,” Ierardi said.

There are currently no known treatments or vaccines for theileriosis, though there are promising results from a drug under testing in Australia.

Theileriosis caused more than $20 million in reduced meat and milk yields in Australia, and the number is closer to $100 million in Japan and Korea, according to published studies from Washington state and New Zealand.

Industry, government and university-affiliated groups are working with producers to try to mitigate the spread and damage.

“This tick species is of great concern, but producers can protect their herd through frequent inspection and by reporting sightings to their veterinarian or local animal health official,” said Dr. Kay Simmons, the chief veterinarian for the National Cattlemen’s Beef Association. “The first step is knowing what to look for.”

But what to look for is only part of the problem.

The symptoms of theileriosis look similar to another bovine disease that is treatable and common.

“That makes it very easy to miss without doing additional lab testing,” Ierardi said.

Jonathan Ahl is the Newscast Editor and Rolla correspondent at St. Louis Public Radio.