If your social media algorithm feeds you as much tick news as it feeds us, you may have seen a new tick mentioned: the Asian longhorned tick, Haemaphysalis longicornis. This tick was first detected in the United States in 2017 and has spread throughout the northeast region. In 2019, our lab received a total of 13 Asian longhorned ticks from within the United States. In 2024, we received 463, over 35 times the number in 2019! As these ticks are becoming increasingly more common to come across, it is important to bring awareness to the risks that they pose.
What is an Asian longhorned tick?
Asian longhorned ticks (ALT) are native to temperate regions of East Asia. It was first reported outside of its native range in 1897, when it was found in Australia. It was detected in New Zealand in 1911 and is also established on several Pacific islands. It was first detected outside of quarantine in the United States in 2017 in Hunterdon County, New Jersey. The most recent case was found in Kansas in October 2025. These ticks have spread throughout the East Coast, ranging as far south as Georgia and as far west as Oklahoma. ALTs have a unique ability: they are parthenogenetic, meaning the females can produce viable offspring without a mate. This ability allows the tick to easily establish itself and proliferate outside of its native range, making it a particularly difficult pest to get rid of.
Risk to human health
There is still much to learn about the Asian longhorned tick, but we know more than we did in 2017. Experimental studies have indicated that ALTs are competent vectors for Rocky Mountain Spotted Fever (Rickettsia rickettsii), Heartland virus, and Powassan virus.
In their native range, ALTs can transmit bacterial, viral, and protozoal pathogens that impact animals and humans alike. Of these, one of the most serious is severe fever with thrombocytopenia syndrome (SFTS), which is caused by the Dabie bandavirus. SFTS can result in severe hemorrhagic fever, leukopenia, and encephalitis. It should be noted that there have been no reported cases of SFTS originating from the US. Additionally, this virus has not been detected in ALTs within the US.
What about Lyme?
Current studies seem to suggest that ALTs will not significantly contribute to the spread of Lyme disease in the United States. A 2020 study by Breuner et. al. found that ALTs experimentally infected with Lyme bacteria lost the infection when they molted. Additionally, a study published in 2019 found that ALTs seem to show an aversion to feeding on the white-footed mouse, which is the primary reservoir of Lyme disease in the wild. However, more research is needed to determine whether ALTs show this same aversion to other wild reservoirs of Lyme disease to determine the true risk of ALTs as a vector for Lyme.
Risk to livestock
In addition to the pathogens listed above, ALTs can transmit Theileria orientalis Ikeda, a highly virulent strain of bovine theileriosis. Bovine theileriosis is caused by a parasite that invades the white and red blood cells in cattle. T. orientalis Ikeda infections have been reported to cause mortality in an average of 1-5% of infected cattle. Bovine theileriosis often leads to reduced milk production, reduced meat production, and miscarriage in pregnant heifers. Animals may also become infested with ticks, which can lead to weight loss, reduced production, and even death. In Australia, the indirect costs of T. orientalis Ikeda are estimated to be $19.6 million per year.
Prevention
Asian Longhorned Ticks are most active from spring through fall. They can usually be found in grassy, shaded areas. It is important to employ normal tick prevention methods, such as doing body checks on yourself and your pets, wearing light colored clothing, and using tick repellent.
What to do if you find an Asian Longhorned Tick?
In the rare instance where you find this tick attached to you, it may be difficult to identify it as an Asian Longhorned Tick with the naked eye. They are usually a reddish-brown color, and their palps or mouthparts give them a “longhorned” appearance. They vary in size, with adult females being only 1/8 of an inch or roughly the size of a sesame seed, nymphs are the size of a poppy seed, and larvae are slightly larger than the head of a pin. Additionally, without inspecting them or being familiar with different tick species, many people would not realize that it is an Asian Longhorned Tick. Therefore, it is encouraged to send in any ticks you find for testing to contribute to tracking tick populations and the prevalence of tick-borne diseases.
References
1Egizi, A., Bulaga‐Seraphin, L., Alt, E., Bajwa, W. I., Bernick, J., Bickerton, M., Campbell, S. R., Connally, N., Doi, K., Falco, R. C., Gaines, D. N., Greay, T. L., Harper, V. L., Heath, A. C., Jiang, J., Klein, T. A., Maestas, L., Mather, T. N., Occi, J. L., . . . Fonseca, D. M. (2020). First glimpse into the origin and spread of the Asian longhorned tick, Haemaphysalis longicornis, in the United States. Zoonoses and Public Health, 67(6), 637–650. https://doi.org/10.1111/zph.12743
2 Yabsley, M. J., & Thompson, A. T. (2023). Haemaphysalis longicornis (Asian longhorned tick). Trends in Parasitology, 39(4), 305–306. https://doi.org/10.1016/j.pt.2022.12.007