The discovery of a foreign species of tick in New Jersey recently has alarmed authorities, who are trying to investigate how it got here. The East Asian or Longhorned tick, which is native to southeast Asia, was first discovered last fall but authorities have just confirmed that they survived the winter, meaning their stay here is likely permanent.

A farmer discovered thousands of ticks while sheering a sheep, and authorities later confirmed that they were Longhorned ticks, which until now were not known to live in the United States. They have no idea how the ticks got here, because the sheep in question has never been out of the country and rarely even leaves the New Jersey county in which it lives.

After discovering the ticks, the New Jersey Department of Agriculture and the National Veterinary Services Laboratory conducted ongoing surveillance of the ticks to see if they would surve the winter and become established in the state. They confirmed this on April 17 after several months of monitoring.

The species can be dangerous in that it carries serious diseases. However, these particular ticks were tested and found not to be carrying any diseases.

“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,” reads a statement from the department. “Until that time, this tick was not known to exist in the U.S. How it arrived in New Jersey remains a mystery.”