TRENTON — How did a tick not known to live in the U.S. wind up on a New Jersey sheep?

The state Department of Agriculture is working with Rutgers and federal biologists to solve the mystery of the bush Tick, found in August on a Hunterdon County sheep that hasn't left its farm in years.

The tick is a serious pest for livestock including cattle, horses, farmed deer, sheep and goats in parts of the world where it has been introduced. It can also be a hazard to wildlife, pets and humans. The sheep is the only animal at the farm where the tick, also known as the longhorned tick, was first found in August.

According to the state Department of Agriculture, it's not known to exist in the U.S., though it's occasionally been found on animals presented for entry at U.S. ports.

Livestock can be vulnerable to a disease the tick spreads called Theileriosis, which results in severe anemia and possibly death, state officials said. But there are no human health or food safety risks associated with Theileria.

But the tick also has the potential to spread other bacterial and viral diseases to humans and other animals, the state said.

"The potential impact of this tick on tickborne illness in New Jersey residents is not yet known. In other parts of the world, the bush tick has been associated with several tickborne diseases, some of which are found in New Jersey, such as spotted fever rickettsioses," New Jersey officials said in an announcement earlier this week.

The sheep's owner brought several ticks to the department, which in turn got help from the Center for Vector Biology at Rutgers University. The United States Department of Agriculture National Veterinary Services Laboratory made positive ID of the tick earlier this month.

The state Department of Agriculture said the tick has been spotted on animals, especially horses, coming into the United States.

The tick is found in East Asia, New Zealand and Australia and is the most widespread tick species on wild and domestic animals in Japan.

It is a non-descript, brown tick. Both males and females of the species are able to feed. However, the invasive form is when females show the ability to produce eggs without a male, as found in the Hunterdon County case, according to state officials.

The Dept. of Agriculture said the property is being treated and is being monitored for additional Bush ticks.

Contact reporter Dan Alexander at Dan.Alexander@townsquaremedia.com or via Twitter @DanAlexanderNJ