An Invasive Tick That Can Clone Itself Is Spreading Across the U.S., Threatening Livestock

Researchers documented three cows in Ohio killed by Asian longhorned ticks, which can lay up to 2,000 eggs without needing to mate

Ticks on a lint roller
Researchers at the Ohio State University collected 9,287 Asian longhorned ticks in just 90 minutes using lint rollers. Risa Pesapane via Ohio State

An invasive species of tick that can clone itself has been spreading rapidly across the eastern United States—and now, researchers have documented a population that killed three cows on an Ohio farm.

This marks the first established population of this species, called the Asian longhorned tick, in the state, according to a paper recently published in the Journal of Medical Entomology. The ticks pose a serious threat to livestock, because they congregate in the thousands and can drain an entire animal of blood. 

“The tick will be a nuisance, and it is spreading,” Kevin Lahmers, an anatomic pathologist at the Virginia-Maryland College of Veterinary Medicine who was not involved with the study, tells Jenny McGrath of Business Insider. “It will cover most of the eastern half of the U.S.—that’s most likely.”

Asian longhorned ticks (Haemaphysalis longicornis) are native to eastern China, Japan, the Russian Far East and Korea, but they were first documented in the U.S. on a New Jersey sheep farm in 2017. In the past six years, the arachnids have spread across 19 states, colonizing new areas incredibly quickly thanks to an unusual reproductive strategy called parthenogenesis. This mode of asexual reproduction allows females to lay about 2,000 fertile eggs without mating.

“There are no other ticks in North America that do that. So they can just march on, with exponential growth, without any limitation of having to find a mate,” Risa Pesapane, a disease ecology researcher at the Ohio State University, says in a statement. “Where the habitat is ideal, and anecdotally it seems that unmowed pastures are an ideal location, there’s little stopping them from generating these huge numbers.”

In 2021, Pesapane received a call from a farmer in eastern Ohio, who reported that three of his 18 cattle had died after being infested heavily with ticks, per the statement. Pesapane and her colleagues visited the property, and in just 90 minutes, they collected more than 9,000 Asian longhorned ticks with muslin cloth and lint rollers. This massive quantity led them to believe the 25-acre property hosted more than one million of the ticks in total.

Anecdotally, Goudarz Molaei, the Connecticut Agricultural Experiment Station’s chief scientist and head of entomology, experienced another large infestation in Connecticut, reports CT Insider’s Vincent Gabrielle.

“There was once incidence in Bridgeport after I walked out of a tick-infested area that I was able to collect 800 ticks just from my coveralls,” Molaei, who was not involved with the recent study, tells the publication.

Though Asian longhorned ticks can carry diseases that infect humans, they are not yet considered a threat to human health in the U.S., per the statement. The parasites don’t seem to be as attracted to human skin as other species of native ticks are. They also appear unlikely to pass on Lyme disease, though, in lab settings, they have been found to transmit other diseases of concern, including Rocky Mountain spotted fever, Heartland virus and Powassan virus, per Business Insider.

After testing 100 ticks sampled from the Ohio farm, the researchers discovered that eight were positive for Anaplasma phagocytophilum, a bacterium that can cause the disease human granulocytic anaplasmosis (HGA). Patients with HGA can experience symptoms such as fever, chills, severe headaches and nausea, but the fatality rate is very low—less than 1 percent. No other diseases were found in any of the other collected ticks.

The researchers are now working on filling in the gaps in knowledge about this tick species and coming up with better management strategies. While pesticides can kill Asian longhorned ticks, the arachnids can easily escape applications by hiding in vegetation, per the statement.

“It would be wisest to target them early in the season when adults become active, before they lay eggs, because then you would limit how many will hatch and reproduce in subsequent years,” Pesapane says in the statement. “But for a variety of reasons, I tell people you cannot spray your way out of an Asian longhorned tick infestation—it will require an integrated approach.”

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