The Asian longhorned tick spreading across the US can clone itself thousands of times and even kill cattle

• Two years ago, a farmer found three cattle dead and covered in a massive number of ticks.
• The ticks turned out to be an invasive species, the Asian longhorned tick, newly established in Ohio.

In the summer of 2021, Risa Pesapane, an assistant professor of veterinary preventive medicine at Ohio State, got a call about three dead cattle on a farm in eastern Ohio, near the border of West Virginia. The farmer had never seen animals so infested with ticks, Pesapane told Insider.

In a recent paper, published in the peer-reviewed Journal of Medical Entomology, Pesapane and her colleagues documented the case, stating it was the first established population of Asian longhorned ticks in Ohio. But Ohio isn't the first place these ticks have turned up.

ALTs are an invasive species native to East Asia. It's been in the US since at least 2010 and found in at least 19 states, according to the US Department of Agriculture.

"The tick will be a nuisance and it is spreading," Kevin Lahmers, a clinical associate professor at the Virginia-Maryland College of Veterinary Medicine, told Insider. "It will cover most of the eastern half of the US — that's most likely."

That's a concern since these ticks not only pose a threat to livestock but, to a lesser extent, people too. "The reason that people are following the ticks so aggressively is because of concern for public health, not just animal health," Lahmers said.

Thousands of Asian longhorned tick clones

When Pesapane and her colleagues showed up at the farm in Ohio, they used a drop cloth and lint roller to collect over 9,000 ticks from around the property in about an hour and a half.

"There were just thousands of ticks present," she said. "I knew immediately that we were not dealing with a tick that we know to be native to the United States."

"They just show up in such incredibly large numbers," Joellen Lampman said. She's an Extension Support Specialist in integrated pest management with Cornell University.

These ticks show up in such large numbers because they can reproduce asexually. None of the experts knew of any other tick species in the US that reproduces this way. On top of that, the ALT can "complete its life cycle in a shorter period of time than the ticks previously native to the United States," Pesapane said.

So, if a female ALT gets transferred all by itself to a new location, it can still establish a new population. "She's basically cloning herself," Lampman said. All her offspring can then go on to lay between 1,000 and 2,000 eggs.

The curious case of the dead cattle

Pesapane and her colleagues suggest the Ohio cattle died from blood loss. However, Lahmers is more skeptical that blood loss, alone, was the culprit.

"It would take an awful lot of ticks in order to take enough blood from that animal to" kill it, Lahmers said, adding that because the cattle were buried before Pesapane arrived, it's difficult to know for sure what killed them.

While Pesapane understands Lahmers' concern, she said that USDA Animal and Plant Health Inspection Service and studies in New Zealand also support the hypothesis that these ticks can cause death in livestock due to severe blood loss.

She added that it's essential to understand the mechanism that kills livestock as the tick spreads. However, it's been difficult to find carcasses to study because cattle owners typically bury them too quickly.

"Some [pathologists] have hypothesized that there may be an interaction between severe anemia and some sort of toxicosis from compounds in tick saliva, but this is just speculation until a study is conducted," Pesapane said.

That said, the cattle's death from another common tick-borne disease, Theileria orientalis, is unlikely since the farm's remaining live cattle tested negative for it, per Pesapane's study.

Lampman noted that similar cattle deaths have happened in North Carolina. "This is not an event that is unique and we're going to see more of it, unfortunately."

Asian longhorned ticks are hard to spot, contain, and kill

Tiny and brown, the ALT is hard to distinguish from other types of ticks, making it difficult to spot.

The ALT seems to thrive in tall grass and wooded areas. While existing pesticides will kill them, they need to come in direct contact with the ticks. "If the ticks are hiding deep down in leaf litter or in dense grass, the pesticides just aren't going to reach," Lampman said.

Controlling an ALT population would take re-application of a pesticide every five weeks, Pesapane said. That's not feasible because the chemicals would affect the grass the cattle eat as well as any pollinators in the area.

Another challenge is that the ticks feed on a slew of different animals. All the experts agreed that animals like cattle and horses seem to be their favorite, but ALTs have been found on dozens of animals.

"It's sort of tasting the buffet of all the new possible hosts in the United States, but it has some sort of tried and true favorites," Pesapane said.

"We're finding them on raccoons, skunks, possums," in addition to deer, dogs, and birds, Lampman said.

Birds and other wildlife may help spread the ticks, especially locally, but Pesapane said moving livestock between states could also be a culprit. "There's probably some combination of wild and domestic animals that are responsible for this" spread, she said.

Asian longhorned tick-borne diseases

In other countries, these invasive ticks spread several pathogens in humans and animals. Right now, they mainly seem to be a threat to animals, but they could potentially transmit diseases to humans, too, Pesapane said.

For example, Pesapane has seen several cases of the disease Theileria orientalis Ikeda in livestock. It causes jaundice and anemia and lowers milk production. Pregnant, infected cows can also lose their fetuses.

"Theileria orientalis Ikeda was not known or not widespread in the United States before this tick," Pesapane said.

This type of Theileria isn't a risk to humans or most other species, Lahmers said. However, the ticks can pass on other pathogens.

While it doesn't seem effective for passing on Lyme disease, the tick has been shown to transmit other human diseases in lab settings. They include Rocky Mountain spotted fever, Heartland virus, and Powassan virus.

Powassan is currently rare but is increasing. With Lyme disease, transmission takes hours. Ticks can pass Powassan on in just 15 minutes, according to the Yale School of Public Health.

"I'm very, very concerned about Powassan virus," Lampman said. "Here's a potentially fatal disease that can get transmitted within minutes. We just don't want to get bit by ticks."

When it comes to staying safe from the ALT, the advice is the same as with other ticks, like covering up bare skin and wearing permethrin-treated clothing. Lampman cites the Swiss cheese method: "The more things that you do, the less likely you are to be bit by a tick."

Pesapane also notes that the ticks seem to love biting dogs, so it's important to protect pets, too.

For livestock, the approach is also similar to dealing with other types of ticks. Pesapane recommends checking animals for ticks, treating infected animals, and maintaining pastures.

All three experts urged people to reach out to their state universities or local agriculture departments if they see an unusual tick.