Deadly Tick-Borne Disease in Cattle

REDFIELD, Iowa (DTN) -- Iowa veterinary officials confirmed the first case of Theileriosis in a cattle herd in southeast Iowa. Theileriosis is a tick-borne disease carried by the Asian longhorned tick (ALHT).

The ALHT was first identified in the U.S. in 2017 by the United States Department of Agriculture, but it's thought to have arrived in the U.S. around 2010 or before. The tick is known to carry pathogens, which cause disease and distress to the host.

According to Iowa's state veterinarian Jeff Kaisand, the case of Theileria orientalis Ikeda is a protozoan parasite carried by the ALHT. He said this parasite infects red and white blood cells and causes bovine infectious anemia.

"There are no approved treatments for Theileria in the United States," Kaisand said in a news release. "The best way to protect livestock is through tick control methods and proper biosecurity to prevent blood-borne spread between livestock."

TICK PRESENCE ALL YEAR

Iowa State University Extension Beef Veterinarian Grant Dewell said ticks can be prevalent in the summer months but tend to have a surge of infection on cattle who are put on a new pasture. "The presence of a preferred host generates a surge in new ticks, as females will begin to lay thousands of eggs," he said.

Dewell recommends cattle producers closely observe animals on pasture for tick infestation. Cattle infected with Theileriosis show signs of lethargy, anemia and difficulty breathing. These animals can also develop ventral edema, exercise intolerance, jaundice and abortions. He said this disease is like anaplasmosis in that younger animals often display more severe signs than mature cows or bulls.

Dewell said controlling external parasites this summer will be important. In addition to insecticide ear tags, he suggested incorporating an insecticide-soaked backrubber or regularly applying pour-on. The products used should include tick control for preventative, which is found on the label. "If an increase in tick infestations is observed, an avermectin pour-on may be the best intervention," he said.

IDENTIFYING THE ASIAN LONGHORNED TICK

According to USDA's Animal and Plant Health Inspection Service (APHIS), the ALHT is light brown in color and very small, around the size of a sesame seed. The adult female is only about the size of a pea when filled with blood. Female ticks can reproduce without a male, producing up to 2,000 eggs at a time.

APHIS said the ALHT has been reported in many eastern states and is slowly moving westward. The pest has also been found in the states of Missouri, Oklahoma, Arkansas and Kansas, with the first report of the ALHT in Michigan last week.

In addition to cattle, Theileriosis can also affect sheep and deer. If a cattle producer suspects Theileria or sees ALHT, they should contact their veterinarian to collect the appropriate samples for testing. This disease is not a threat to humans.

Jennifer Carrico can be reached at jennifer.carrico@dtn.com

Follow her on social platform X @JennCattleGal

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