Asia’s Longhorned Tick Takes Its First Documented Bite In The U.S.

Tick bites man.

That's not exactly news, but it is in the case of a particular tick that bit a particular man. The tick, native to Asia, is Haemaphysalis longicornis, also known as the longhorned tick. It was only recently discovered in North America.

And now, for the first time, there's a record of a bite by the longhorned tick in the U.S.

The bite, which took place last year, is documented in a journal report published in late May in Clinical Infectious Diseases.

The tick's victim, who lives in Westchester County, New York, has not become ill as a result of the bite. But health experts are keenly aware that in Asia, and in Australia and New Zealand, where the tick is found as well, it is known to spread pathogens that can be lethal to humans and animals.

One such pathogen is SFTS virus, a potentially fatal hemorrhagic fever. SFTS is not found in North America but is similar to the Heartland virus, which is present in North America and can be transmitted by ticks, according to Dr. Bobbi Pritt, director of the Clinical Parasitology Laboratory at the Mayo Clinic. So far there is no evidence that the longhorned tick carries this virus.

The longhorned tick was first formally detected in the U.S. on a sheep in New Jersey in 2017. No one knows exactly how the tick made it to North America, and tick experts say it's possible that it arrived earlier than that.

As for the documentation of the first bite, Rick Ostfeld, senior scientist at the Cary Institute of Ecosystem Studies in New York State and a tick specialist, cautions that longhorned ticks have probably bitten humans in the U.S. before — but no one realized the bite came from a different species of tick.

And this species is definitely different from other ticks — in ways that are potentially worrisome to humans.

First, female longhorned ticks can reproduce without the aid of a male. A single female can lay thousands of eggs, which will hatch into more females.

And while the more common U.S. tick, the blacklegged tick, is usually found in the woods and in tall grass, the Westchester County man reported that he had not been in the woods in the 30 days prior to the bite, just on his mown lawn and another lawn. That's an environment where people are not currently advised to take precautions against ticks.

The Centers for Disease Control and Prevention is working with the U.S. Department of Agriculture, the Northeast Regional Center for Excellence in Vector-Borne Diseases at Rutgers University and state health departments "to investigate where and how widespread the tick is and whether or not it can spread pathogens to animals and people in the United States." Lars Eisen, a research entomologist with the CDC's division of vector-borne diseases in Fort Collins, Colo., says research is ongoing this summer in the Northeast "to clarify the types of environments where you can be exposed to longhorned ticks."

For now, the CDC hasn't changed its recommendations for preventing tick bites. Eisen says that based on the most current information, the methods that CDC recommends to prevent bites by other tick species are likely to be effective against the longhorned tick: using EPA-registered repellents on skin and clothing as directed, for example, and frequent tick checks soon after coming indoors "from potentially tick-infested areas, including your own backyard." The CDC and the Environmental Protection Agency offer more recommendations about the longhorned tick and on repellents.

Ostfeld thinks that new tick precautions may be in order given the probable location of the human bite on a well-trimmed lawn in sunlight (per the bite victim's description). "We might want to expand the types of habitat types people have to be concerned about," he says.

But he is also concerned about causing "tick fatigue." You don't want to "make your warnings so dire that people start to think they can't do anything about it or avoid out-of-doors altogether," says Ostfeld.

Bobbi Pritt says it's a good thing that more attention is being paid to the longhorned tick. The USDA, for example, is issuing regular reports on which states are involved: so far, Arkansas, Connecticut, Kentucky, Maryland, New Jersey, New York, North Carolina, Pennsylvania, Virginia, Tennessee and West Virginia. "A lot of people are interested, and a lot of projects are starting," she says.

One underway is The Tick Project, run by Ostfeld and Felicia Keesing of Bard College and conducted in neighborhoods in New York state. The project is testing products against placebos: for example, a fungus to kill ticks (instead of chemicals that would kill other less dangerous critters) and "bait boxes" that lure mammals such as mice and apply a tiny drop of a tick-killing chemical that doesn't harm the mice. Ticks feeding on mice are most likely to become infected and dangerous, specialists say, so these are the most important to target.

In the meantime, scientists are forecasting more bites from this Asian tick. The longhorned tick "is known to bite people in other parts of the world so we would expect to see occasional human bites in the United States as well," says Eisen of CDC.

But there's not a sense of panic at this point. Eisen says, "We do not yet know if this tick is as likely to bite people as other ticks of concern to human health in the United States." And Ostfeld says it's even possible that the longhorned tick is not especially attracted to humans as hosts — "but we don't know that yet."

Fran Kritz is a health policy reporter based in Washington, D.C. Her work has appeared in The Washington Post and Kaiser Health News. Find her on Twitter @FranKritz

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