Extension Notebook: Asian longhorned tick infestation was just a matter of time

I was hoping that this wouldn’t happen, but Illinois is just another state in the U.S. where the Asian longhorned tick (Haemaphysalis longicornis) has infested a farm. This distinction is definitely nothing to brag about nor unexpected.

In August a farmer noticed his cattle were lethargic with large numbers of ticks, particularly under the tailhead and udder, the tail head and the scrotum of the herd bull. Ticks were collected and sent for identification. They came back as Asian longhorned tick, or ALT.

After being notified about the ALTs, my colleagues from the Illinois Natural History Survey Medical Entomology Lab and I drove to the farm to survey the pasture, sampling for ticks where cattle became infested.

Tick sampling involved dragging a 100-meter-long drag path starting at a random location at six distinct locations at the farm. This approach uses a cloth attached to a dowel and pulled along behind a person by a cord attached to each end of the dowel. During the sampling event cotton flannel cloth was pulled along the ground and examined at 5-to–10-meter intervals along the drag. Ticks found attached to the drag cloth and clothing of sampling personnel were removed using forceps (nymphs and adult ticks) or lint rollers (larval ticks). Afterwards the collected ticks were identified to species using standard taxonomic keys and enumerated by life stage at the lab.

We were amazed at the sheer number of ticks, especially larvae. All life stages were present — larvae, nymph and adults — but by far larvae numbered in the thousands, even possibly millions when considering the acreage. The pasture had numerous cattle paths, hilly with trees and creeks running through, some swampy areas and other areas were brushy with open grass. The region had received ample rain all spring and early summer.

The farm provided the ideal environment — timber/brush with swampy and grassy areas — and Mother Nature provided the moisture for ticks. My colleagues at INHS-MEL have been documenting the movement of ticks and tick-borne diseases in Illinois. We know that native ticks are expanding their geographic range, increasing in abundance and cases of tick-borne disease is increasing not only in Illinois but in the U.S. However, the ALT movement in this state is confusing.

The Asian longhorned tick was first reported in Morgan and Hamilton counties in 2024. My research found ALT in Clay and Pope counties in 2025, and Marion, Franklin and Wayne counties this year. Basically, except for Morgan County, the tick is south of I-70 and east of I-57.

However, a wrench has been thrown into that idea — the latest county is Henry, in northwestern Illinois.

Henry County, like Morgan, does not border any counties with known populations of ALTs. So how did the tick arrive on a closed-herd farm? I have several ideas, but the first that comes to mind are migrating birds. Illinois is on the Mississippi Flyway where over 300 bird species migrate. This tick is well documented to attached to several species of birds — e.g. great horned owl, northern cardinal, house wren, blue jay, Carolina wren, bald eagle, and Canada goose. A bird could have picked up a single tick further south, dropped it on the farm then flew on north. A second possibility is the movement of larger wildlife such as white-tailed deer, bobcats, black bear, and mountain lions. A third possible scenario is people traveling with their pets. People visiting and/or vacationing in areas where the tick is endemic could bring the tick back on their clothing or pets. Regardless how the tick arrived, it is definitely there and unfortunately will be there for a very long time.

So, what is next for livestock in the infected area? Once ALTs have been identified on a property where livestock are pastured, it becomes important to inspect those animals on a regular basis. Areas that should receive extra attention are: head, neck, ears, flanks, armpit, groin, udder and under the tail (areas where the skin is thinner). The most common areas ticks attach on cattle are around the tailhead, on the udder, inside the legs, on the brisket, in the ears (particularly near the insertion sites of ear tags) and occasionally on the face and neck.

Why is it important to monitor livestock more closely once the ALT has been identified on your farm? This tick is parthenogenic, which means it does not need a male to reproduce. An adult ALT female can deposit approximately 2,000 eggs and from there the numbers can compound. Weather, habitat and available suitable hosts will impact ALT’s survivability and ability to multiply.

Cattle infested (several hundred to thousands have been reported in the U.S.) with ALT have been reported to lose weight, become anemic and, in some cases, die. The ALT is also a vector for Theileria orientalis Ikeda and Chitose, an intracellular protozoal parasite responsible for theileriosis in cattle. Theileriosis can cause poor weight gain, poor performance, late-term abortions, and in some cases even death.

Theileriosis and anaplasmosis clinically present the same, but only a blood test can tell the difference. It is important to have your herd vet test for both when ALT are suspected to be present. Unfortunately, there no treatment options for theileriosis, unlike anaplasmosis, but cattle should be provided supportive care. Once theileriosis has been found in the herd it will spread rapidly and to calves every calving season.

A single pesticide application in spring and fall may not be effective against ALTs. Consider using other application methods during the year such as pesticide-impregnated back rubs and side rubbers and ear tags. It has been recommended not to use permethrin impregnated ear tags to avoid resistance. Use pour-ons for heavy or extreme tick numbers and apply at the midline in a narrow strip.

It is important to treat all animals in the herd for ticks at the same time. Apply formulations specifically labeled for tick control. Follow all label recommendations for all pesticides (including ear tags, backrubbers, pour-ons, etc.) used, including time to retreat, withdrawal periods, beef vs. dairy, lactating vs dry, use of personal protection, etc.

Chemical treatment of pastures is not generally recommended except when tick populations are extremely large and then only areas with the highest numbers of ticks. While chemical treatment can reduce tick burden, it will not eliminate the chance of ticks, tick bites or acquiring a tick-borne disease such as Theileriosis.

Other management recommendations include: keep pastures edges mowed low, mow pastures high ahead of moving cattle, control brush, and keep cattle out of wooded or swampy areas. Leaving pastures unmowed or ungrazed will not impact ALT numbers much since they can survive around a year without feeding. Also, managing ALT can be very difficult because this tick spends most of its life off the host and on the ground and wildlife, such as deer, small mammals, and birds, serve as alternative hosts for ticks, aiding in their spread throughout pastures.

This tick will keep spreading to unreported areas, so vigilance is now key to livestock management. If you suspect large numbers of ticks are infesting your cattle, call your herd veterinarian. Contact me (tsteckle@illinois.edu) for additional information if you suspect ALT on your farm and/or need verification of tick specie present.

Teresa L. Steckler is a University of Illinois Extension Specialist, commercial agriculture.