Asian Longhorned Tick Continues to March Westward

Livestock | March 2026

Written by:

Jennifer Ryan has been writing about veterinary topics for nearly 20 years. She has a master’s degree in journalism, a bachelor’s degree in agricultural communications and decades of experience caring for both livestock and pets.

The Asian longhorned tick (ALT) has now been found in 24 states and as far west as Oklahoma. ALT was first discovered in the United States in 2017 but may have been here since 2010. The tick is a carrier of Theileria orientalis, a strain that is pathogenic to cattle and causes the disease Theileriosis. In North Carolina and Ohio, cattle have died from Theileriosis as a result of ALT infestations.1

A spread that’s unlikely to stop

ALT spreads into about three new states a year, noted Pete Teel, Ph.D., research professor and entomologist with Texas A&M AgriLife Research. The reasons for the continued spread include:

  1. Human movement of infested animals
  2. Transportation of cattle across the country
  3. The local and extended range of both domesticated and wild animals ALT uses as hosts

“As we move companion animals, livestock and wildlife throughout the country, we risk transporting ticks from one location to another. Right now, we don’t have requirements for animal inspection or treatment against ALT so it’s quite easy to move these guys around,” Dr. Teel said.

The first discoveries of ALT in a new county or state often occurs on cattle or dogs, further demonstrating how the movement of people, domesticated animals and cattle make containing the ALT difficult.

Tick identification

Looking for the tick is critical to identifying it in your herd, explained Joellen Lampman, tick and school IPM coordinator with the Cornell Integrated Pest Management Program.

“We’ve actually been surprised at how slowly it has spread in New York. We were expecting it to spread much faster than it has,” she said. “In livestock, we see it mostly impact beef herds in our area. These are not animals that are being looked at regularly. Also, some people don’t know there is more than one type of tick.”

Lampman and colleagues at Cornell University spent the summer of 2022 scouting for the tick across the Capital and Hudson Valley regions. Their efforts confirmed the tick on domestic pigs in the United States. Since then, Lampman has been accepting tick photos to help producers with identification on their operations.

Most ticks are not easy to identify. It’s even more difficult with ALT larvae and nymphs, which are all very small. In addition, the tick hides in cracks and crevices of the animal like under the legs or belly. These are areas humans rarely inspect thoroughly, Dr. Teel noted.

.

Minimize risks

Right now, traditional tick and parasite control measures are the best solution to minimizing the risk for cattle. This includes implementing biosecurity measures such as:

  • Keeping closed herds whenever possible
  • Inspecting and treating new animals for ticks
  • Placing new animals in holding pens before being released into
    the herd
  • Cleaning holding pens and trailers
  • Habitat management (controlling overgrown weeds, grasses, etc.)

Additional protocols may be necessary for producers in areas where the ALT is established.

“Making good biosecurity measures a priority is essential. Any time you’re breaking the skin of the animal — injecting or dehorning or castration or eartagging — equipment should be disinfected and single-use needles are required,” Teel said. “Otherwise, you’re at a high risk of moving Theileria or even the agent of anaplasmosis between cattle through mechanical transmission.”

Currently available acaricides work against the ALT. However, most products currently on the market will not have ALT on the product label since this is a relatively new pest to the United States, he said.

Future outlook

Eastern and Midwest producers should brace for identification of ALT on their operation and familiarize themselves with USDA APHIS protocols for documenting an infestation. The first step should be contacting their veterinarian, who will work with state and local officials.

Future control measures are being developed and evaluated with funding from organizations like the Foundation for Food & Agriculture Research, which began receiving ALT-related research proposals as early as 2019. Two projects included developing a biological control tool for ALTs and evaluating the efficacy of spray and pour-on tick treatments for cattle.

“The Asian Longhorned Tick arrived in the U.S. in 2017, without clear indications of how it came to the U.S. The tick began multiplying quickly and spreading to additional states. Since then, the tick has continued to rapidly spread west. This spread has been rapid due to asexual reproduction, which allows the tick to multiply exponentially,” explained Miriam Martin LeValley, Ph.D., scientific program manager at the Foundation for Food & Agriculture Research. “The economic losses posed by this pest are significant, and FFAR’s goal is to find solutions to the biggest challenges facing food and agriculture. Continuing to fund research on the tick is one way we are achieving that goal.”

Key Points:
  • 24 states identified the tick that carries the disease, including states as far west as Oklahoma.
  • Most infected cattle have limited or mild clinical signs. The symptoms are very similar to anaplasmosis.
  • May see sudden death, especially in late pregnant and early lactation cows.
  • Asian longhorned ticks use a range of wild and domesticated animals as hosts. Adult ticks can be found on cattle, horses, deer and sheep, and also have been found on humans, cats, dogs, pigs, goats, bears, foxes, raccoons and rabbits.

Image Credit:

istockphoto.com/Ilja Enger-Tsizikov

istockphoto.com/davidf

>