Researchers went to the pasture and dragged a muslin cloth along the ground, using a lint roller to pick up the sesame seed-sized creatures, which balloon to the size of a pea when feeding on blood. They managed to gather 9,287 ticks in just 90 minutes.

Then, they tested 100 of the females for diseases. Eight had Anaplasma phagocytophilum, a tick-borne disease that can harm humans and animals. But the disease was not present in the surviving herd, and scientists concluded the cows had likely died of blood loss. The ticks have returned to the pasture despite pesticide treatment.

Researchers blame female ticks’ ability to asexually reproduce in the thousands, and ticks’ knack for hiding in tall grass and surviving harsh conditions, for the infestation and similar situations in other states. Pesticides must touch individual ticks to be effective, and treatment is most effective before adults lay their eggs.

“You cannot spray your way out of an Asian longhorned tick infestation,” said Risa Pesapane, assistant professor of veterinary preventive medicine at Ohio State and the paper’s senior author, in a news release. Instead, the researchers call for better surveillance and integrated management.

According to the Centers for Disease Control and Prevention’s website, the ticks have been spotted in Arkansas, Connecticut, Delaware, Georgia, Indiana, Kentucky, Maryland, Massachusetts, Missouri, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia and West Virginia.

Research on the invasive ticks is ongoing. It is unclear whether they can pass germs along to humans in high enough quantities to cause disease.

Officials recommend using insect repellents and permethrin-treated clothing to keep ticks at bay and say to remove them from people and animals as soon as possible. If you do see a tick, save it and contact your health department. Researchers in Ohio and elsewhere are eager to learn more about the bugs.

“They are going to be a long-term management problem. There is no getting rid of them,” Pesapane said in the news release.