An exotic tick from East Asia that infested a sheep in one New Jersey county has now been confirmed in a second county, according to the New Jersey Department of Agriculture.

The confirmation is another sign the longhorned tick, Haemaphysalis longicornis, has become established in the state — its first known presence in the U.S.  The confirmations have made it even more urgent to find how far it has spread and how to best control it.  The two locations are about 40 miles apart.

Though not necessarily an immediate threat to people, the tick nonetheless has the potential to infest a range of species, including dogs, cats, and livestock, the department said in a statement issued Wednesday.

The first infestation occurred in August 2017 on a sheep and its one-acre paddock in Hunterdon County.  The infestation was so severe that ticks swarmed the pant legs of investigators when they went to the site in October.  Officials thought the pest might have been killed off over the winter but recently discovered it had survived.

The newly confirmed presence at Watchung Reservation in Union County actually predates the sheep infestation, tracing back to May 2017 during a routine collection of ticks for a study.  The National Veterinary Services Laboratory in Iowa confirmed this week that one of those ticks was a longhorned tick.

And just last week, federal and state wildlife officials were combing the same area for presence of the longhorned tick when they found what appeared to be one on a white-tailed deer.  On Tuesday, the veterinary lab confirmed the tick was a longhorned. It was the first time the pest had been found on wildlife in the state.

Local, state, and federal animal health officials, as well as Rutgers University, are working together to identify the range of the ticks and develop a plan to eliminate the pest.  In addition, the Rutgers University Center for Vector Biology and the Monmouth County Mosquito Division will host a "tick blitz" in May to educate all mosquito control commissions in New Jersey on the new pest.

Part of the problem in detecting the arachnid's spread is its size.  Longhorned ticks are similar in size to deer ticks, and their nymphs resemble tiny spiders, so it's easy to miss them.   The ticks can easily go unnoticed on animals and people.

The tick is native to Japan, the Korean peninsula, and China.  But it has recently become a major problem in New Zealand, where it transmits a disease in animals called theileriosis, which can lead to anemia and is potentially fatal.  The tick has also become a problem for cattle in Russia, Australia, and several Pacific Islands.  How it spread to New Jersey is still a mystery.

Andrea M. Egizi, an author of the Rutgers study on the longhorned tick infestation in New Jersey, said previously that the tick has been associated with rare diseases found in people, such as spotted fever rickettsiosis.  But she said scientists need more information before they can assess whether the new tick poses a threat to local residents.

She said the tick transmits human pathogens in its native range in Asia, but only on occasion, and usually affects only people who are in contact with livestock. Those pathogens are not normally present in U.S. soil.  The question, she said, is whether the longhorned tick can transmit pathogens native in the U.S.

However, the study notes that New Jersey already "has one of the highest burdens of Lyme disease in the nation, accounting for almost 14 percent of all cases reported in 2015."