Disclaimer: This article is for informational purposes only and does not constitute pest treatment or veterinary advice. Livestock owners should contact the New York State Department of Agriculture and Markets or their local Cornell Cooperative Extension office with specific concerns.

The Short Version

Most invasive species stories start somewhere else and work their way toward New York. This one started here.

In July 2018, a tiny tick species new to New York State was confirmed in Westchester County. It was the first documented case anywhere in the state. Eight years later, the Asian longhorned tick has spread through the Hudson Valley and reached farther north than ever recorded, during the 2026 season.

It's not a human health threat based on current evidence. It is a serious, fast-moving problem for livestock, and it can start a new infestation with a single tick.

2,500
Eggs one female tick can lay, without ever mating
Source: Smithsonian Magazine, reporting on the species' parthenogenetic reproduction.

A Tick That Doesn't Need a Mate

Female Asian longhorned ticks reproduce through parthenogenesis. That means a single female can lay fertile eggs entirely on her own, up to 2,000 to 2,500 in a season. Males are rare, and in most established populations, they aren't needed at all.

In practical terms: one tick riding in on a pet, a deer, or a piece of farm equipment is enough to establish a breeding population in a matter of weeks. There's no bottleneck waiting for a second tick to show up.

The Westchester Origin Story

2013

First identified in the United States, in New Jersey.

2018

First confirmed in New York State, in Westchester County. It has since been found in Virginia, West Virginia, Arkansas, and North Carolina.

2025

Just 2 of 20 monitored Hudson Valley farms had confirmed populations.

2026

Every one of those same 20 monitored farms now has confirmed populations. New York's northernmost detection reached Kinderhook, in Columbia County.

Timeline compiled from NYS Department of Agriculture and Markets and Westchester County Department of Health reporting.

Screenshot of the Westchester County Department of Health's Longhorned Tick page, confirming the July 2018 first detection in Westchester County
Westchester County's own health department page on the longhorned tick, confirming the 2018 first detection. View the live page.

Why Livestock Owners Should Actually Worry

Heavy infestations aren't a nuisance for farm animals. They're dangerous on their own. Enough ticks feeding at once can cause severe blood loss and anemia in cattle, sheep, and goats, sometimes fatal without the tick spreading any disease at all.

The tick can also carry theileriosis, a parasite that damages red blood cells and reduces milk production in cattle. Northern Westchester and the surrounding Hudson Valley have real horse and small-livestock populations, which puts local hobby farms in the same exposure zone as the commercial operations already reporting problems.

Not a Human Health Threat, So Far

Testing of longhorned ticks in New Jersey for pathogens that sicken people has come back negative to date. Westchester County's health department states plainly that the tick does not pose a risk to human health at this time. That could change as more research is done, but there's no evidence of it right now.

What to Watch For

At 2 to 3 millimeters, adult longhorned ticks look like a dark speck of dust on skin, grass, or clothing. That size is exactly why infestations often go unnoticed until numbers are already high.

  • Check animals regularly, especially around ears, neck, and legs, where ticks cluster in heavy infestations.
  • Watch for unusual numbers of tiny ticks in one spot. A cluster of dozens in a small area is a longhorned tick signature, not typical of native species.
  • Report suspected sightings to the New York State Department of Agriculture and Markets, Division of Animal Industry, or your county extension office.
  • Standard tick prevention still applies to pets and family, including permethrin-treated clothing and routine tick checks after time outdoors.

Frequently Asked Questions

Is the Asian longhorned tick dangerous to people?

Not based on current evidence in the United States. Testing of longhorned ticks in the Northeast has not turned up any pathogens known to sicken people, and Westchester County's own health department says it does not pose a risk to human health at this time.

Where was the Asian longhorned tick first found in New York?

Westchester County, in July 2018. It was the first confirmed detection of the species anywhere in New York State. It had already been identified in New Jersey in 2013.

Can one Asian longhorned tick start an infestation?

Yes. Females reproduce through parthenogenesis, meaning they can lay fertile eggs without mating. A single female can lay up to 2,000 to 2,500 eggs, so one tick reaching a yard or pasture is enough to establish a population.

What animals are most at risk from the Asian longhorned tick?

Livestock. Cattle, sheep, and goats are most affected, since heavy infestations cause blood loss and anemia, and the tick can spread theileriosis, a disease that reduces milk production. Dogs and horses can also pick up ticks, though the primary documented risk is to farm animals.

Next Move

The tick that started its New York story in Westchester in 2018 is now spreading faster than researchers expected. If you keep horses, chickens, or other livestock in northern Westchester or the surrounding Hudson Valley, check animals regularly through the fall for unusually dense clusters of tiny ticks.

For everyone else, this stays a livestock story for now, not a family pest control story. Standard tick prevention for people and pets already covers the risks that actually apply to your household.

Sources

Last updated: August 23, 2026

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