Authorities are alarmed after an exotic species of tick suddenly showed up in New Jersey last year, and they now appear to be a permanent resident of the state. The New Jersey Department of Agriculture has annoujnced that the East Asian tick, also called the bush tick or Longhorned tick, has managed to survive the winter after it was first discovered at a farm last year.

The department says that ongoing surveillance was conducted through the winter, and on April 17, the National Veterinary Services Laboratory confirmed that the tick had overwintered and is now established in the state. The tick was first discovered after a farmer foujnd thousands of ticks while shearing a sheep.

They were eventually identified as Longhorned ticks, which are not known to exist in the United States. Authorities are not sure how the species got here, as the sheep has not traveled outside of the country and only rarely leaves the county. This species of tick can carry serious diseases, although the ones that were examined did not.

“Following initial identification by the Center for Vector Biology at Rutgers University and the Hunterdon County Department of Health, the National Veterinary Services Laboratory (NVSL) in Ames, Iowa confirmed on November 9, 2017 the finding of an exotic East Asian tick (Haemaphysalis longicornis), also known as the Longhorned tick or bush tick, on a farm in Hunterdon County,” the department said in a statement. “Until that time, this tick was not known to exist in the U.S. How it arrived in New Jersey remains a mystery.”