An exotic tick previously unknown to the United States is spreading across the eastern United States with sightings in seven states this summer.

The Asian or longhorned tick, Haemaphysalis longicornis, has been found in Arkansas, New Jersey, New York, North Carolina, Pennsylvania, Virginia and West Virginia.

Native to East and Central Asia, the tick was thought to have been found for the first time in the United States after it was located on a farm in Hunterdon County, New Jersey, in November, but the U.S. Department of Agriculture's National Veterinary Services Laboratory recently confirmed a tick taken from a dog in Union County, New Jersey, in 2013 also was a longhorned tick.

An invasive species that congregates in large numbers, the longhorned tick can cause anemia in livestock. It is known to carry several diseases that infect hogs and cattle in Asia. So far, ticks examined in the U.S. do not carry any infectious pathogens.

In early August, authorities said the tick was discovered on a wild deer in Centre County, Pennsylvania. In New Jersey, a tick was found in a wooded area in the central part of Bergen County in July during a routine collection of ticks by the county entomologist, said Alicia D’Alessandro, a county spokeswoman.

The appearance in the region has prompted health officials to warn residents to take precautions when they are outside.

“Ticks can be found in your own backyard, so it is essential to wear long sleeves and pants, use insect repellent containing DEET to help keep you safe from ticks and the diseases they carry," said Pennsylvania Secretary of Health Dr. Rachel Levine. "It is also important to check yourself and your pets for ticks, as pets can bring ticks indoors.”

Easily confused with other tick species, including the rabbit tick, which is common in the Eastern U.S., the species’ distinctive “horns” may not be visible without a microscope. The Asian tick infests host animals in dense clusters of numerous ticks. Female Asian ticks reproduce asexually, so a single tick can reproduce and lay 2,000 eggs after feeding on a host. Cattle, pets, small mammals, birds and humans are all potential hosts.

Haemaphysalis longicornis tick
The Haemaphysalis longicornis tick, known as the “longhorned tick,” was recently discovered in seven states. The photo shows the top row black-legged/deer tick family; the center are poppy seeds; while the bottom are nymph and adult longhorned ticks
NYS Health Department

Unfed ticks can live nearly a year. They have been found on a variety of wild animals, birds, pets and humans. An infestation spreads quickly in farm animals.

“Even experts have difficulty distinguishing among tick species, so it is important to take precautions to protect pets, livestock and family members from becoming a host for ticks of any kind,” said Pennsylvania Veterinarian Dr. David Wolfgang. “Scientists don’t yet know how this species will adapt to the North American climate and animal hosts, but we know it survived New Jersey’s winter and has infested sheep and cattle in this region.”

The longhorned tick can transmit an animal disease called theileriosis to livestock. The disease can reduce milk production in dairy cows and cause blood loss in and the occasional death of calves. Sheep farmers can see poorer wool.

Health officials do not know whether the longhorned tick is capable of transmitting Lyme disease but it has been shown in Asia to spread other serious diseases such as SFTS virus and the pathogen that causes Japanese spotted fever along with many diseases in animals. SFTS, or severe fever with thrombocytopenia syndrome, is an emerging infectious disease that can be fatal.

"Our entomologist says there should be no more or less concerns about this tick than any other," D’Alessandro, of Bergen County, said. "The basic precautions should be followed."

New Jersey officials have been on the lookout for the species ever since it was identified last fall. How it got on the Hunterdon County sheep is unclear since the sheep had never been out of the country and had been grazing alone for years.

“Taking steps to protect yourself, your children and pets against ticks is the best way to prevent tick bites and tickborne diseases," said New York state Health Commissioner Howard Zucker.

"We will continue to conduct surveillance and research on this new type of tick, but it is encouraging that the same steps that protect against deer ticks are also effective against the longhorned tick.”

The longhorned tick was found in multiple locations in Westchester County, New York, in July, the state health department said.

It was identified in New York by the Health Department in conjunction with researchers at Fordham University and the Lyme Disease Diagnostic Center of New York Medical College.

Safety tips from the New York State Department of Health:

- Wear long pants and long-sleeved shirts to protect against ticks other biting insects.
- Check for ticks often while outdoors and brush off any ticks before they attach.
- Perform a full body check multiple times during the day.
- Consider use of repellents containing DEET, picaridin or IR3535, following label instructions.
- If you have been bitten by a tick of any kind, contact your health care provider immediately if you develop a rash or flu-like symptoms.