Asian Longhorned Tick

Asian Longhorned Tick & Theileriosis in Cattle: 10 Key Facts

Mon, 22 Jun 2026 20:54:02 GMT

The Asian longhorned tick (ALHT) is not your typical tick. No longer a problem confined to a handful of Eastern states, the invasive tick has spread to 27 states since its first U.S. detection in New Jersey in 2017. As it moves west and south into new cattle country, producers and veterinarians who have never dealt with the tick — or the disease it carries, theileriosis — are facing a steep learning curve.

Asian longhorned tick life stages and relative actual size.

(Photos of unfed ticks by Centers for Disease Control. Photos of engorged ticks by Jim Occi, Rutgers, Center for Vector Biology.)

Unfed ALHTs range from a light reddish tan to a dark red/brown. While the adult female grows to the size of a pea when full of blood, other stages of the tick are very small — about the size of a sesame seed. Once blood fed, adult females are a grey green with yellowish markings, similar to native ticks. Male ticks are rare.

(New Jersey Department of Agriculture)

APHIS reports it only takes a single tick to create a population in a new location. ALHTs need warm-blooded hosts to feed and survive. They have been found on various species of domestic animals — such as sheep, goats, dogs, cats, horses, cattle and chickens — and wildlife. The tick has also been found on people.

Kansas State University Extension entomologist Cassandra Olds warns cattle producers ALHT and theileriosis are a challenge that is both wideespread and a long-term concern.

“While New World screwworm, has received a lot of attention, we have great tools to deal with the outbreaks and eventually re-eliminate the pest,” she explains. “For ALHT and bovine theileriois, it will be a problem that we have to deal with indefinitely.”

Olds and Virginia Tech Veterinarian John Currin have witnessed the tick and tracked the disease for years. Here are the 10 things they say every producer needs to understand about ALHT:

1. ALHT Can Reproduce Without a Mate.

Unlike most tick species, the ALHT can reproduce asexually. A female can lay up to 2,000 eggs at a time without ever encountering a male. That reproductive shortcut is a major reason populations can explode in a single season once the tick establishes in an area.

(Cassandra Olds)

Biologically, the ALHT is a three-host tick, meaning each life stage — larva, nymph and adult — feeds on a different host.

2. Double Threat: The Tick And The Parasite It Carries Is

ALHTs carry Theileria orientalis, a protozoan parasite that infects red and white blood cells, causing anemia and, in severe cases, death. Bovine theileriosis is the disease caused by Theileria orientalis.

Heavy tick infestations alone can also stress an animal enough to reduce performance — USDA APHIS has noted that a dairy cow can see a 25% drop in milk production simply from the burden of feeding ticks, independent of any disease they transmit.

Olds says because theileriosis can spread without the tick being present through biting insects like lice and shared needle use, this isn’t just a problem where ALHT is already established.

3. Once An Animal Is Infected, It Carries Theileria For Life.

There is no cure. An infected animal becomes a chronic carrier and the parasite can flare back up any time that animal faces significant stress — shipping, weather, weaning or calving. That’s why high-stress groups deserve extra attention long after the initial outbreak has passed.

4. The Disease Looks Completely Different In Calves Than In Adult Cattle.

Currin says in animals over about a year old, theileriosis tends to mimic anaplasmosis. In calves under a year, it more closely resembles pneumonia. In both cases, the giveaway is that the animal won’t respond to antibiotics no matter how many doses it receives — because there is no direct treatment for theileriosis, only supportive care.

5. Watch For An Animal Going Off Feed — Don’t Wait For Anemia.

By the time an animal shows visible anemia, the disease has often progressed significantly. Earlier warning signs include loss of appetite, severe lethargy, a dejected or “droopy-headed” appearance, fever, coughing or labored breathing, and rapid weight loss. Sick animals also tend to be unusually withdrawn rather than aggressive, a contrast to the behavior often seen with anaplasmosis.

6. Mortality Is Highest During The Initial Outbreak.

Olds reports mortality rates due to Theileria range from 5% to 20%, with the highest mortality occurring when the pathogen is first introduced to a herd. Once an area becomes endemic and most animals are exposed as calves with maternal protection still active, severe outbreaks become far less common.

7. In Endemic Areas A Positive Test Means Almost Nothing.

This is one of the most important lessons from areas that have lived with the tick the longest. Currin, who has treated cattle through Virginia’s Theileria outbreak since 2017, put it this way: “The tick epidemiology is — I’ll use a scientific term — weird.”

Currin reports more than 90% of herds in his part of Virginia are infected, many without producers ever knowing it. His key takeaways for producers in newly affected areas:

99% of herds will experience minimal problems.
Most infected animals show no significant clinical signs.
The disease primarily causes anemia.
There’s no direct treatment available.
Positive tests are now almost meaningless in endemic areas.

8. As A Region Becomes Endemic, The Disease Shifts From Cows To Calves.

Currin has watched this play out in Virginia: Theileria initially hit adult pregnant cows hardest when the disease was new to the area, but now more commonly affects 2-month-old calves in spring-calving herds. The reason is straightforward — there is no in-utero transmission of Theileria, so “every calf starts naive,” Currin says.

Roughly 80% of calves in infected herds become positive by three months of age, though most never show severe clinical signs.

9. Feedlot Performance Impact Appears Minimal.

Contrary to early fears, Currin says research has found no significant difference in weight gain between Theileria-positive and Theileria-negative cattle in a feedlot setting. Olds adds death loss can still occur from outbreaks.

Currin says his primary concern instead lies with cow-calf operations bringing naive animals into already-infected areas — not with finishing cattle that test positive.

10. This Isn’t A Fight You Can Win By Keeping The Tick Out — It’s One You Manage.

Veterinarians and researchers across affected regions agree on this point: Producers cannot realistically prevent the ALHT and Theileria from eventually reaching their operation. The goal instead is knowing your herd’s status, watching high-risk animals — young, pregnant, recently weaned or recently shipped — more closely, and having a working relationship with a veterinarian who can respond quickly when an outbreak hits.

Olds notes the Theileria can spread through tick bites and through shared veterinary needles. She says her team is currently researching the role of biting flies in transmission. She stresses the importance of maintaining animal health and reducing stress to prevent disease outbreaks.

“Keep animals happy and healthy. Stress does weird things to immune responses,” she adds.

According to Olds, these strategies can help control AHLT:

Burning pastures in regions where this is permitted
Keeping grass short and removing woody encroachment
Careful use of insecticides
Pasture rotation

There are currently no labeled treatments for the disease or a definitive cure. Typically, treatment focuses on secondary issues and providing basic care. Olds suggests producers avoid mass injecting ivermectin, as it can cause resistance to other pest populations like biting flies and native ticks and harm beneficial insects like dung beetles..

Medgene has developed a tick vaccine that is designed to work on multiple tick species, including ALHT. Veterinarians can purchase directly from Medgene. The vaccine requires two initial doses, followed by yearly booster shots.

Olds says the goal is to achieve “endemic stability” — when most animals are exposed early and develop lifelong immunity with minimal disease symptoms.
She emphasizes community-level management over eradication.

“The Asian longhorned tick and Theileria are not going away, and it is not a producer’s fault if the disease appears,” she summarizes. “Many herds are likely already infected without obvious illness.”

Instead of trying to keep it out forever — an unrealistic goal — she encourages producers to know their herd’s status through testing, plan how they move cattle in and out, stay vigilant with high-risk groups and continue doing business while adapting to this new endemic reality.

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The Asian Longhorn Tick Moves West to Kansas

Fri, 10 Oct 2025 15:34:59 GMT

The Asian longhorn tick (ALHT) has now been identified in Kansas . The tick was submitted to the Kansas Department of Health and Environment for identification after being found on a dog in Franklin County last week. This represents the western most occurrence of the tick; it was last found in Iowa in June, 2025.

ALHT was first identified in the U.S. in 2017 in New Jersey. Since then it has gradually spread westward and has been documented in 21 states according to USDA .

These ticks are a threat to both human and animal health. ALTH are known to carry Theileria, a protozoan parasite that infects red and white blood cells. Theileria can lead to anemia and even death. Typically, cattle affected by Theileriosis will show signs of lethargy and difficulty breathing.

Because the female tick can reproduce without a male and lay up to 2,000 eggs at a time, a single tick can lead to a major infestation on a single animal leading to reduced growth and production, and, in the most severe cases, death from blood loss.

Cattle producers should be on high alert for external parasites on their animals. While their activity might decrease in the winter months, the ALTH can survive for up to six months off an animal and is tolerant of the cold.

For more information on the ALHT, check out:

Beef Producers Be Aware: Dangerous Asian Longhorned Tick Continues Migrating West

Theileria and the Asian Longhorned Tick: What Beef Producers Need to Know

Theileria and the Asian Longhorned Tick: What Beef Producers Need to Know

Wed, 06 Aug 2025 16:56:39 GMT

The Asian longhorned tick (ALHT) poses a serious threat to cattle health. ALHTs carry Theileria, which is a protozoan parasite that infects red and white blood cells. It can lead to anemia and, in some cases, death.

In the U.S., ALHT was first detected in New Jersey in 2017. Since then, it has spread to more than 20 states. With the recent discovery of ALHT in southeast Iowa , the Iowa Cattlemen’s Association hosted a webinar lead by Cassandra Olds, Kansas State University Extension entomologist, who explained the tick and pathogen background, its potential impacts, best practices for prevention, as well as caring and treatment strategies.

“This was always a when, not an if,” Olds explains. “You did absolutely nothing wrong. If you have the tick or the pathogen, this was an inevitable thing.”

What We Know about ALHT and Theileria

Biologically, the ALHT is a three-host tick, meaning each life stage — larva, nymph and adult — feeds on a different host. Olds says unlike other tick species, it can reproduce asexually, with all adult ticks being females capable of laying eggs without mating. This characteristic allows for rapid population growth, as a single tick can potentially establish an entire population.

Once an animal is infected with Theileria, it becomes a chronic carrier for life, with the potential to relapse during high-stress periods. The pathogen replicates in red blood cells, causing anemia and a range of symptoms including loss of appetite, weight loss, fever and respiratory issues.

Olds says while the first year of exposure can be challenging, long-term production impacts are typically minimal. The key is to approach the situation with knowledge, preparedness and a calm, strategic mindset.

She stresses that just because a cow herd does not have the symptoms doesn’t mean it doesn’t have Theileria. It just means that if an animal was infected, it didn’t develop the disease.

She reports mortality rates due to Theileria range from 5% to 20%. With the highest mortality when pathogen is first introduced — the outbreak. An animal can have a relapse of disease, often during high stress or immune compromising events.

She explains the high-risk animals are young (under 6 months), pregnant animals, stressed animals and any naïve animal moving into an area with previous outbreaks.

Best Practices for Prevention

Olds notes the pathogen can spread through tick bites and through shared veterinary needles. She says her team is currently researching the role of biting flies in transmission.

She stresses the importance of maintaining animal health and reducing stress to prevent disease outbreaks.

“Keep animals happy and healthy. Stress does weird things to immune responses,” she adds.

According to Olds these strategies can help control AHLT:

Burning pastures
Keeping grass short
Careful use of insecticides
Pasture rotation
Ear tags and pour-ons

(Data: Oklahoma State University; Tick Photo: J.A. Cammack)

Real-World Experience

Veterinarians John Currin and Austin Williams share their firsthand experiences with ALHT and Theileria.

Currin serves as associate professor and production management medicine with the VA-MD College of Veterinary Medicine at Virginia Tech. He says in his area more than 90% of the herds are infected and many don’t know they’re infected.

“The tick epidemiology is — I’ll use a scientific term — weird,” he says.

He explains as the disease became endemic in Virginia, its clinical presentation changed. While it initially affected adult pregnant cows, it now more commonly impacts 2-month-old calves in spring calving herds.

“There is no in utero spread of this organism, so every calf starts naïve,” Currin says.

Approximately 80% of calves in infected herds become positive by 3 months of age, though most do not show severe clinical signs.

He adds contrary to initial concerns the Theileria appears to have minimal impact on cattle in a feedlot. Currin says research found no significant differences in weight gain between negative and positive cattle.

He stresses the primary concern is for cow-calf operations bringing naive animals into infected areas.

Currin shares these key points about Theileria:

99% of herds will experience minimal problems
Most infected animals show no significant clinical signs
The disease primarily causes anemia
There’s no direct treatment available
Positive tests are now almost meaningless in endemic areas

Williams serves producers in northwest Arkansas and southwest Missouri.

“I think it’s been here longer than we recognize and it’s more widespread than what we realize it too,” he says. “I would say some states have it that don’t know they have it.”

In Williams’ area he has seen the tick infestation become widespread. The key challenges he’s witnessed is the difficulty of managing the tick population and the potential for secondary health issues in infected cattle.

He recommends individual herd management strategies, including regular checks, treatment plans and potentially moving infected herds to different pastures.

Treatment Strategies

There are currently no labeled treatments for the disease or a definitive cure. Typically, treatment focuses on secondary issues and providing basic care.

Avoid mass injecting ivermectin, as it can cause resistance and harm beneficial insects like dung beetles.

“Please don’t just mass inject everybody with ivermectin because you’re worried about the Asian longhorned tick,” Olds says.

Vaccine Developed

Medgene has developed a tick vaccine that is designed to work on multiple tick species, including ALHT. Veterinarians can purchase directly from Medgene. The vaccine requires two initial doses, followed by yearly booster shots.

Williams says he’s had clients use the vaccine this year, and he’s hopeful about the vaccine’s potential and is waiting for more research from the University of Arkansas to provide concrete data on its effectiveness.

Gary Bosch, Medgene executive vice president, says animals should be vaccinated before they encounter ticks.

“In the Southern U.S. where ticks are a year-round problem, early vaccination is especially crucial because the Asian longhorned tick can overwhelm an animal very quickly,” he says.

Industry Impacts

Olds says the goal is to achieve “endemic stability” — when most animals are exposed early and develop lifelong immunity with minimal disease symptoms.

She emphasizes the need to remove the stigma associated with the tick or pathogen presence, noting that infection is an inevitable part of agricultural reality. Producers should focus on proactive testing, management and community support.

To prepare for and to deal with Theileria, Olds recommends producers:

Establish a good relationship with a veterinarian
Conduct regular herd testing
Maintain low-stress environments
Implement careful tick control measures
Share information and support each other as a community

Her final advice is to be vigilant but not panicked.

“Producers should view the Asian longhorned tick as a manageable challenge rather than a catastrophic threat,” she summarizes. “By working together, maintaining animal health and implementing smart management strategies, the agricultural community can effectively navigate this emerging issue.”

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Beef Producers Be Aware: Dangerous Asian Longhorned Tick Continues Migrating West

Wed, 18 Jun 2025 13:24:33 GMT

The Asian Longhorned Tick (ALHT) poses a serious threat to cattle health. ALHTs carry Theileria, which is a protozoan parasite that infects red and white blood cells. It can lead to anemia and, in some cases, death.

ALHTs are native to eastern Asia, eastern China, Japan, the Russian Far East and Korea but were introduced to Australia, New Zealand and western Pacific Islands. In other countries, it can also be called a bush tick, cattle tick or scrub tick.

In the U.S., ALHT was first detected in New Jersey in 2017. Since then, it has spread to more than 20 states with recent confirmations in Illinois , Michigan and Iowa .

According to USDA’s Animal and Plant Health Inspection Service (APHIS) ALHTs are known to carry pathogens, which can cause disease and may also cause distress to the host from their feeding in large numbers. For example, a dairy cow may have a 25% decrease in milk production after becoming a host.

A female can reproduce without a mate and lay up to 2,000 eggs at a time. This can cause great stress on a heavily infested animal and result in reduced growth and production. A severe infestation can kill the animal from excessive blood loss.

Asian longhorned tick life stages and relative actual size.

(Photos of unfed ticks by Centers for Disease Control. Photos of engorged ticks by Jim Occi, Rutgers, Center for Vector Biology.)

What does it look like?

Unfed ALHTs range from a light reddish-tan to a dark red with brown, dark markings. While the adult female grows to the size of a pea when full of blood, other stages of the tick are very small — about the size of a sesame seed.

Adult females are a grey-green with yellowish markings. Male ticks are rare.

APHIS reports it only takes a single tick to create a population in a new location.

The above photos are of a AHLT engorged (on the left) and an adult AHLT not engorged.

(New Jersey Department of Agriculture)

ALHTs need warm-blooded hosts to feed and survive. They have been found on various species of domestic animals — such as sheep, goats, dogs, cats, horses, cattle and chickens — and wildlife. The tick has also been found on people.

What are the health risks?

APHIS says ALHTs are not known to carry Lyme disease, but they can cause tickborne diseases affecting humans and animals such as:

Rocky Mountain spotted fever
Heartland virus
Powassan virus

APHIS says those diseases have not been confirmed outside of a laboratory setting in the U.S. In addition, U.S. ALHT populations can transmit U.S. Theileria orientalis Ikeda strain (Cattle theileriosis) in the laboratory.

In an Iowa State University release , Grant Dewell, Extension beef veterinarian and associate professor, says cattle affected by Theileriosis will show signs of lethargy, anemia and difficulty breathing. They may develop ventral edema, exercise intolerance, jaundice and abortions.

“Although signs of Theileriosis are similar to anaplasmosis, younger animals and calves often display more severe signs compared to mature cows and bulls,” he says. “Due to anemia from both tick infestation and Theileria, the risk of death can be elevated. If cattle producers suspect either Theileria or ALHT, have a veterinarian collect appropriate samples and submit them to a veterinary diagnostic lab.”

According to an Oklahoma State University press release , under laboratory conditions ALHT is a competent vector of numerous pathogens that can cause disease in humans, including Rickettsia rickettsii (Rocky Mountain Spotted Fever), Heartland Virus and Powassan Virus.

In “ Clinical Infectious Diseases, ” Bobbi Pritt, MD, MSC, with the division of clinical microbiology at the Mayo Clinic in Rochester, Minn., reported a human bite that occurred in New York in 2019. She says though the report of a human bite isn’t surprising, it proves the invasive longhorned tick continues to bite hosts in its newest location.

“This is extremely worrisome for several reasons,” she writes. “One reason is Asian longhorned ticks can carry several important human pathogens, including the potentially fatal severe fever with thrombocytopenia syndrome (SFTS) virus and Rickettsia japonica, which cases Japanese spotted fever. While these pathogens have yet to be found in the United States, there is a risk of their future introduction.”

Also, Pritt says several other human pathogens have been detected in the ticks, but it’s not clear if the ALHT species are able to transmit them to humans. They include Anaplasma, Ehrlichia, Rickettsia, and Borrelia species. Lyme disease is caused by Borrelia burgdorferi bacteria.

She warns the organisms are present in states where ALHTs have been found and that it’s possible the tick — known to be an aggressive biter— might be able to transmit Heartland virus given its close relationship to SFTS virus.

How to Tackle Ticks

According to APHIS, various strategies effectively mitigate tick populations on hosts and in the environment.

Regular tick treatments should be effective against ALHTs. Consult your veterinarian or agriculture extension agent about which products to use.
Check your livestock for ticks regularly.
Safely remove ticks from people and pets as quickly as possible. If you think you’ve found an ALHT, seal it in a zip-top bag and give it to your veterinarian for identification.
Habitat modifications can help prevent ticks on feedlots and pastures. This may include mowing grass, removing trees, reducing shade by thinning trees, understory removal and placing mulch barriers.
Apply acaricide using label instructions to tick habitats, such as woodland edges and grassy patches, during times when ticks are most actively seeking hosts. Although it varies by year, ALHTs are generally active from March to November. Consult your state and local regulations for approved acaricides.

“Cattle producers should aggressively control external parasites this summer,” Dewell summarizes. “Insecticide ear tags alone are not enough to control ticks. Consider incorporating a back rubber or regularly applying a pour-on during the summer. Pyrethroid-based products are also available that include a tick control label. If an increase in tick infestations is observed, an avermectin pour-on may be the best intervention.”

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Invasive Tick Found in Boone County, Arkansas

Tue, 15 Apr 2025 16:58:26 GMT

A tick found in a Boone County cattle herd has been confirmed as the invasive Asian longhorned tick, known for carrying a parasite that can be deadly to cattle.

The Asian longhorned tick, also known as bush, cattle or scrub tick, was first found in Arkansas in 2018 on a dog in Benton County. The tick can kill its host by swarming the animal but can also transmit a protozoan parasite called Theileria orientalis. One Theileria genotype, Ikdea, can impact cattle by attacking blood cells.

Since its arrival in Arkansas, the Asian longhorned tick has been confirmed in Benton, Independence and Washington counties with Boone County added last month.

Three researchers with the University of Arkansas System Division of Agriculture are collecting ticks as part of a broad surveillance project. They include extension entomologist Kelly Loftin; veterinarian and animal science professor Jeremy Powell; and assistant professor of entomology Emily McDermott. The team aims to evaluate the prevalence of Asian longhorned ticks in Arkansas, determine whether Theileria orientalis is present in the tick population and evaluate host preference.

“Surveillance efforts in 2024 began in April and we’ve seen a significant increase in the Asian longhorned tick population from both on-animal and environmental tick collections,” Loftin said. “In our 2023 collection efforts we found eight to 10 ticks at our site in Batesville and this year we found over 200. That site in Batesville has the most dramatic increase I’ve seen.”

In addition to the spread of the tick, more confirmed cases of Theileria orientalis have recently been confirmed in Arkansas cattle with Boone and Searcy counties reporting cases.

“Arkansas producers should be aware of the risk of Theileria infection in their cattle herd, but not alarmed,” said Maggie Justice, beef cattle extension specialist for the Division of Agriculture. “Understanding how the disease spreads and the best methods of prevention are important in helping herds, so it’s important producers utilize resources and knowledge available through their veterinarians and local county extension agents.”

Justice said cattle that are infected may look like those that have been impacted by anaplasmosis, a tick-borne disease common in Arkansas. She added that signs of sickness can make the animal appear weak and “off” with an abnormal attitude, not eating and decreasing gains.

The Division of Agriculture, the Arkansas Department of Agriculture and the Arkansas Cattlemen’s Association are partnering to host a webinar to discuss how to look for the Asian longhorned tick, signs of Theileria orientalis infection, prevention methods and more.

The webinar will be at 6 p.m. on July 11 and is free to attend. Those interested can register online.

To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit www.uaex.uada.edu. Follow us on X and Instagram at @AR_Extension. To learn more about Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website: https://aaes.uada.edu. Follow on X at @ArkAgResearch. To learn more about the Division of Agriculture, visit https://uada.edu/. Follow us on X at @AgInArk.