The Asian longhorned tick (Haemaphysalis longicornis) was discovered in the U.S. in 2017, and it poses health threats to both animals and humans. A new guide in the Journal of Integrated Pest Management outlines the different management strategies that are being developed, and surveillance and prevention are key to reducing this non-native arthropod’s impact. Shown here are a nymph (left) and adult female. (Photo by James Gathany, CDC Public Health Image Library)

By David Coyle, Ph.D.

David Coyle, Ph.D.

In 2017, a tick was found on a sheep on a New Jersey farm. Normally, that’s not a big deal (mammals get ticks all the time), but this was no ordinary tick—it turned out to be the Asian longhorned tick (ALT, Haemaphysalis longicornis), which was new to the U.S. Because this tick looks very similar to other Haemaphysalis ticks in the U.S., scientists did some digging and found that this tick had, in fact, been present in the U.S. since at least 2010! While we’ll likely never know exactly how this new invasive species got here, these findings served as the impetus to understand the biology, ecology, and potential impacts of ALT on U.S. livestock, pets, and humans. What we know so far about ALT is outlined by the Tick Team at Western Connecticut State University’s Tick Lab, led by Neeta Connally, Ph.D., in an article published in October in the Journal of Integrated Pest Management.

Native to China, Japan, the Koreas, and the Russian Far East, ALT is currently found in several eastern U.S. states. ALT feeds on a wide range of hosts, but seems to prefer larger mammals such as sheep, horses, and cows. Temperature and humidity are very influential in ALT’s ability to thrive—colder and drier conditions tend to limit ALT populations, while warm and humid conditions contribute to more rapid population growth and increased activity. Models suggest that ALT would thrive in much of North America. This species is largely parthenogenic, meaning males aren’t required for females to produce viable eggs—in fact, only one male has been found in the U.S. so far. While this is a fascinating biological trait, it’s also an unfortunate one in that even a single female can start a new population.

Asian longhorned ticks (Haemaphysalis longicornis) can often be found questing in clusters on tall grass (A and B), and a cluster will commonly “explode” when something brushes against them, such as a host animal or human or, in this photo, a drag cloth used for monitoring for the ticks’ presence. (Photo originally published in Schappach et al 2020, Journal of Integrated Pest Management)

The Asian longhorned tick has the potential to carry several medical and veterinary disease organisms, including Anaplasma, Babesia, Borrelia, Ehrlichia (the causal agents of anaplasmosis, babesiosis, Lyme disease, and ehrlichiosis, respectively), as well as Powassan virus. But, just because ALT can carry the microorganism doesn’t necessarily make them a vector component—in fact, a recent study showed that ALT cannot transmit Borrelia burgdorferi. Of greater concern in the U.S. is ALT’s possible transmission of Theileria, which impacts livestock, and Heartland virus, which can affect humans.

So, what now? Are we resigned to daily tick checks and tucking our pants into our socks every time we go for a walk in the woods during tick season? Well, yes; that’s just good practice. I don’t know about you, but I’d rather do that than have to remove a tick from my undercarriage. According to Connally, “At this point, personal protection against ALTs is the same as what we recommend for other human biting ticks: performing tick checks, wearing repellent, and showering/bathing soon after being outdoors. They do commonly feed upon dogs, so treating your pet with an effective tick preventative product all year long is also very important.”

In areas where ALT is present (or might soon be present), surveillance programs have been initiated, and the development of integrated pest management programs (including vaccinations and the use of synthetic and biorational pesticides) is being prioritized. There is some thought that altering the physical habitat of lawns and pastures by keeping grass short and removing woody debris may also help reduce ALT populations. But as with any medically important pest, avoiding them in the first place is by far the best medicine.

David Coyle, Ph.D., is an assistant professor in the Department of Forestry and Environmental Conservation at Clemson University. Twitter: @drdavecoyle. Email: dcoyle@clemson.edu.