An invasive species of tick that is known for its tendency to infest livestock is now confirmed to have spread to a fourth New Jersey county, state officials announced Tuesday.

The state also said that it has found evidence that the tick has been in New Jersey since 2014, much longer than had been previously known.

The Longhorned tick, also known as the East Asian tick, has been found in Mercer County according to the New Jersey Department of Agriculture.

Jeff Wolfe, a spokesman for the NJDA, said that the tick was found in the northern part of Mercer County, near the border with Hunterdon County. The Mercer County tick was found in tall grass near a wooded area; the same kind of habitat that the ticks in elsewhere.

"Long, tall grass next to wooded areas seems to be the common element here," Wolfe said.

The NJDA also announced that a tick taken from a dog in Union County in 2013 has been confirmed to be a Longhorn tick, meaning that the invasive species in been in New Jersey since at least then. The 2013 tick had been recently reexamined by Rutgers scientists before being sent to the U.S. Department of Agriculture's National Veterinary Services Laboratory, which confirmed the identification.

The tick, which was first found in Hunterdon County and has also been found in Union County and Middlesex County, is not considered a threat to people in the Garden State. The NJDA has yet to find any diseases being carried by the tick in New Jersey. Wolfe said that the U.S. Department of Agriculture is planning to do more testing for possible diseases carried by the tick.

Wolfe urged people to use normal tick prevention methods on themselves and their pets.

The major concern for the state is the tick's potential impact on animals like cattle, horses, deer, sheep and goats. The NJDA has called the longhorned tick "a serious pest to livestock."

The state's efforts to fight the ticks have so far been to treat the specific areas where the ticks are found.

"If we find ticks in a specific area, we will do what we can to eliminate them from those known sites of infestation," said Manoel Tamassia, the New Jersey State Veterinarian. "We will work to continue to identify the areas of the state where the tick is so we can help prevent its spread."

The tick's initial sighting in Hunterdon County marked the first time the species had been found in North America. It is not known how the ticks made their way across the Pacific to rural New Jersey.

Elsewhere in the United States, the tick has since been found in Virginia and West Virginia. It is unknown if those sightings are related to the ticks arrival in New Jersey.

The Mercer County tick was found in as part of a "tick blitz" organized by Rutgers, in which Rutgers scientists searched for ticks in all of New Jersey's 21 counties.

A tick hotline has also been established by the NJDA. To leave a message if a tick is found and there is uncertainty about what the next steps are, or if you need information about what to do if you find a tick on yourself, your pets or livestock, call 1-833-NEWTICK (1-833-639-8425).

Michael Sol Warren may be reached at mwarren@njadvancemedia.com. Follow him on Twitter @MSolDub.