Asian Longhorn tick remains a concern to cattle producers

As Missouri cattle producers prepare to push cow herds out on pastures, experts advise them to watch for the invasive pest, the Asian Longhorn tick, that causes severe weight loss and death in cattle lurking in the fields.

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University of Missouri researchers of the College of Veterinary Medicine found the tick on a Linn County pasture last summer. The finding marked the northernmost appearance of the tick in Missouri. It also appeared in June 2021 near Springfield.

Found in 17 states since 2017, the Asian Longhorn tick is a significant concern for cattle producers, says Rosalie Ierardi, an anatomic pathologist at the MU Veterinary Medical Diagnostic Laboratory. Hundreds of the ticks can attach to a single animal, causing irritation and significant blood loss.

Ierardi says the tick can spread quickly. Females produce up to 2,000 eggs at a time. Since females can reproduce without mating with males, a single female can introduce a population of ticks into a new area.

The biggest reason veterinarians are concerned about this tick is that it transmits a parasite of cattle, Theileria orientalis Ikeda, which destroys red blood cells. Cattle will show symptoms including jaundice, weakness, and spontaneous abortions. The symptoms closely resemble those of bovine anaplasmosis, which is widespread in Missouri. A blood test is needed to tell the two diseases apart.

"Currently, there is no approved treatment for Theileria orientalis Ikeda," says Ierardi. "Management typically focuses on reducing tick numbers and minimizing the impact of stress and other health issues that may affect a cow's ability to mount a strong immune response."

Producers can reduce risk by keeping cattle away from wooded areas and other habitats where ticks live, and clearing weeds and brush regularly. They should also consider inspecting cattle for ticks during handling events, says Ierardi. Livestock markets might provide opportunities for spread, so checking or treating new introductions is especially important. For specific herd health advice, farmers should consult their veterinarian.

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Native to Korea, China, Japan, and eastern Russia, the longhorned tick has been a well-established invasive species in Australia and New Zealand for over 70 years.

The tick will continue to spread within North America in the coming years, leading to increased transmission diseases to cattle and possibly also to humans, according to Ierardi's Ph.D. adviser, Ram Raghavan.

Raghavan, an professor in the College of Veterinary Medicine and the School of Health Professions, has tracked the spread of ticks in the U.S. for more than 15 years. He led a 2019 study that determined regions of the U.S. that would be suitable for establishment of the invasive longhorned tick. His findings have been supported by real-world data over the last several years.

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Like other ticks, the Asian Longhorn can easily travel unnoticed on livestock, humans, and pets. Its hosts include cattle, deer, dogs, humans, raccoons, opossums, and other domestic and wild animals.

While the tick transmits several human diseases in the regions where it originated, there is no evidence at this time that they transmit any human diseases in the United States, says Ierardi. Laboratory studies show that the tick can transmit Rocky Mountain spotted fever.

Currently, researchers are studying the tick closely to learn more about how to manage this potential risk.

There are various strategies for farmers to avoid being bitten by the Asian Longhorn are the same as those for other ticks. Learn more here.

If you think you may have found an invasive tick, contact your local veterinarian, extension specialist or health department for assistance to have the tick identified.