MSU Extension Beef

Why are Michigan producers suddenly talking about the Asian Longhorned Tick?

The Asian Longhorned Tick (Haemaphysalis longicornis) poses a serious threat to livestock health. By taking blood meals, or by serving as a parasite vector, it can cause anemia, particularly in young animals or those experiencing stress (e.g., transport, calving) and, in some cases, death. Therefore, it is important to be aware of the presence of this tick and to diligently scout for Asian longhorned ticks on livestock and companion animals.

Asian longhorned ticks are native to East Asia, including Russia, China, Korea and Japan, but have spread to Australia, New Zealand, the Pacific Islands and the U.S. In other countries, Asian longhorned ticks are often called a bush or scrub tick. Although Asian longhorned ticks have been identified throughout the eastern U.S. since 2010, they are migrating westward. In June 2025, the Michigan Department of Agriculture and Rural Development confirmed the first detection of two Asian longhorned ticks in southern Michigan.

The Asian longhorned tick life cycle generally spans two years with three stages: larval, nymph and adult as described by Penn State Univ. experts (see photo). Asian longhorned ticks in the U.S. are parthenogenic, meaning females can lay eggs without the use of males for reproduction. Female ticks usually lay their eggs in late spring and early summer, depending on temperature and humidity. In late summer, larvae, about the size of a pinhead, climb nearby vegetation and wait with front legs outstretched for a suitable host, in a behavior called questing. Blood-fed larvae will then drop off the host, overwinter and molt into a nymph the following spring. Nymphs, which are about the size of a poppy seed, again climb vegetation to seek a second host and blood feed. Dropping off a final time, the nymph will molt into an adult, now about the size of an apple seed, to seek a final host mid-summer. After this final blood meal, the adult female, which when full will reach about the size of a pea, will drop off the host. After this final feeding, they may produce up to 3,000 eggs over a two- to three-week period, according to Matt Playford, DVM, who has experience with Asian longhorned ticks in Australia. Due to this ability, a single stowaway tick can produce a dense population of ticks in one grazing season.

How can Asian longhorned ticks hurt my livestock operation?

Many ticks, including Asian longhorned ticks, can spread pathogens that may infect livestock, including Anaplasma, Babesia, Borrelia, Ehrlichia, Rickettsia and Theileria. Perhaps the most worrisome is that Asian longhorned ticks can transmit Theileria orientalis, a protozoa parasite, which does not affect human health, but can affect cattle, buffalo, equine and wild ruminants. T. orientalis consists of three primary subtypes: Buffeli (theoretically benign), Chitose (variable pathogenicity), and Ikeda (virulent). T. orientalis Ikeda infects cattle, resulting in the disease bovine theileriosis, which is a nationally reportable disease and has no U.S.-approved treatment. Bovine theileriosis is caused when T. orientalis (primarily Ikeda) invades cattle’s red and white blood cells and triggers infectious anemia in beef and dairy cattle. Adult Asian longhorned ticks do not transfer T. orientalis to the eggs, so larvae, nymph and adults obtain the parasite from feeding on an infected host.

Research conducted in New Zealand indicates that sheep apparently may be carriers of T. orientalis Ikeda and are capable of infecting ticks that feed upon them. Research in goats shows that they can be reservoirs of various Theileria subspecies too, however, both sheep and goats lack clinical signs of disease when infected by T. orientalis, and appear to maintain normal productivity.

Once infected, cattle remain carriers of T. orientalis, allowing new ticks and other blood-feeding parasites to become spreaders of T. orientalis after consuming a blood meal. Additionally, bovine theileriosis may spread among animals with needle reuse or via transplacental transmission. USDA APHIS reports clinical signs of theileriosis mirror those of bovine anaplasmosis and may include anemia, jaundice, weakness, late-term abortions, persistent subclinical infections and even death. Herd cattle mortality rates have approached 10-15% in newly affected areas of the U.S. Previous infection with any subtype of T. orientalis can protect from clinical disease due to antibodies developed. In endemic areas, calves 2 to 4 months of age or cattle that are stressed (e.g., calving, heat stress, nutritional stress, excitable animal handling) are most vulnerable to succumbing to theileriosis. Meat & Livestock Australia estimates the indirect costs of T. orientalis Ikeda to the Australian beef industry, including reduced meat and milk yields, is $19.6 million per year. According to Kevin Lahmers, DVM, PhD, Veterinary Pathologist, Virginia Tech Animal Laboratory, comparable cost estimates for the U.S. are $300 million annually.

Tick infestations on their own may cause general unthriftiness, lethargy, and anemia in cattle, sheep, and goats. Anemia can be identified by pale mucosal membranes (e.g., around the eyes, mouth and vulva). Milk and weight gain production losses may be expected in addition to hide damage.

When and where should I look for ticks?

Field studies in New York show nymphs peak in spring, adults in midsummer and larvae in early fall. Routinely inspect, both visually and by feel, livestock, pets and humans for ticks. Experience with Longhorned Ticks in Ohio and elsewhere suggests that inspection in animals should focus on the face, head, neck, ears (particularly inside ears and ear tag insertion sites), flanks, armpits, inside of legs, groin, udder and tail head/anus (areas with thinner skin). If ticks are identified, and one is trying to identify on-farm hot spots, one may drag shaded, humid pasture margins with a light-colored cloth to sample questing ticks according to this guide. Since Asian longhorned ticks spend a relatively short time feeding on the host in each life stage, most of the tick’s life is spent in the environment.

Will it help to modify my pastures or wooded areas?

Environmental management practices, such as maintaining short vegetation and removing brush and woody debris from pasture edges, have been tested by University of Wisconsin-Madison researchers and can reduce tick habitat. One of the most useful methods to decrease tick encounters with livestock is maintaining a closely mowed 20-foot minimum buffer zone between pastures and wooded areas. Asian longhorned tick counts, documented by researchers from the University of Tennessee, dropped dramatically over two years on a Tennessee cow-calf farm that combined monthly brush-cutting with other control methods. Fencing livestock out of wooded, brushy areas and creek draws removes key tick refuges. Because early spring and late fall tend to be the most active times for ticks, particularly avoiding these times in wooded areas could help control infestations. Preventing known wildlife hosts (e.g., whitetail deer, raccoons, opossums) from entering livestock paddocks will further help control the spread of Asian longhorned ticks from wildlife to livestock.

Can I use pesticides to control ticks in my pastures or on my livestock?

Pesticides specifically designed to kill ticks and mites are called acaricides. Effective management of ticks requires a multifaceted approach, and acaricides are typically used in combination with other environmental control measures and only after those control measures have provided inadequate control, although there is no established treatment threshold for Asian longhorned ticks on livestock. Acaricides can be applied through impregnated ear tags, topicals (i.e., pour-ons, rubs, sprays) or injectables. There are no acaricides currently approved for use in U.S. livestock with a label claim against the Asian longhorned ticks specifically. However, there are several classes of parasiticides (e.g., pyrethroids/pyrethrins, avermectins/milbemycins, organophosphates) that will control a variety of external parasites, such as flies, lice and ticks. Spraying or fogging pasture buffer zones is also an option, but the sprays must directly contact the tick for control (low or no residual efficacy). A searchable database of registered pesticides, including acaricides, based on state, livestock species, pest, and application method, is available. It is important to treat all animals in a herd simultaneously and to strictly follow all label instructions regarding pesticide applications, including withdrawal periods and retreatment intervals. Rotation of classes of products is necessary to prevent parasite resistance to their widespread and prolonged use. Consult with your veterinarian, local Extension educator and/or) pesticide representative to tailor control measures to specific herd and regional conditions. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.

Do I need to be concerned with buying or comingling livestock?

If combining cattle from an Asian longhorned tick endemic area with those of an Asian longhorned tick free area, cattle native to the Asian longhorned tick free area will have an increased likelihood of developing clinical symptoms of theileriosis because of environmental vectors of the T. orientalis Ikeda and their lack of immunity. Keep in mind, T. orientalis Ikeda can be transferred between animals by modes other than Asian longhorned tick bites (e.g., other biting insects, common needles). Similarly, combining cattle from Asian longhorned tick-free areas with those from Asian longhorned tick-endemic areas increases the risk to cattle moving into the tick-endemic area due to lack of previous exposure to T. orientalis Ikeda. If cattle are moving from tick-free to tick-free or tick-endemic to tick-endemic areas, there would be no appreciable increase in disease risk.

Acquiring livestock from regions where the Asian Longhorned Tick is endemic poses a risk of introducing the disease into previously unaffected areas. While theileriosis may not be a significant concern for sheep and goat producers, the inadvertent introduction of ticks can still present serious health consequences. Therefore, it is essential to identify endemic pest species in the source region, isolate and inspect all new arrivals for parasites, and, if necessary, treat animals with appropriate acaricides before integration.

What management adaptations can I adopt as a livestock producer?

Think layered defense. No single tactic is likely to eliminate Asian longhorned ticks, and successful control will come from combining, habitat modification, external parasite control, and thoughtful biosecurity.

What should I do if I find a tick?

1. Download The Tick App and report any tick you see. The app is available at https://tickapp.us or through the Apple Store and Google Play. The app connects with experts who can attempt tick identification from a photo.
2. Submit the tick for testing if you find one on your pets or livestock, to the Michigan State University Veterinary Diagnostic Lab.
3. Alert neighbors. Coordinated control over contiguous acres protects everyone.

If you have concerns with external parasites in your livestock or would like to discuss this topic further, please contact the authors, who are Michigan State University Extension Animal Agriculture Team members. We would be happy to talk to you about developing or revising a plan to control external parasites. We also recommend that you discuss all herd health-related issues with your veterinarian to maintain a good client-patient relationship.