Dr. Ram Raghavan Photo courtesy of Kansas State University

Dr. Ram Raghavan, a spatial epidemiologist at Kansas State University, collects longhorned ticks near Queensland, Australia, where he spent a month studying the natural habitats and wildlife hosts of longhorned ticks. Of the nearly 900 tick species found around the world, about 90 make their home in the United States. Now, a new international report indicates that another species has joined the group and is on the move throughout North America.

According to spatial epidemiologist Ram Raghavan, BSc, MS, PhD, an assistant professor at Kansas State University College of Veterinary Medicine and lead author of the report, invasive populations of Haemaphysalis longicornis-longhorned ticks-are expected to become established in many parts of the North America.

Where are the danger zones?

Indeed, the invasion has already begun, with the species newly discovered in many U.S. states, including New Jersey, New York, West Virginia, Virginia, North Carolina, Maryland, Connecticut, Pennsylvania and Arkansas.

The Asian longhorned tick, Photo courtesy of the CDC

The Asian longhorned tick.

Using multiple spatial distribution models, Dr. Raghavan and his team evaluated the likelihood of this dangerous tick migrating to other areas of the continent.

“We have identified vast areas of North America, particularly the southeastern U.S., the West Coast and broad areas of the northwestern U.S., as well as central and southern Mexico, as climatically suitable for establishment of this species,” says Dr. Raghaven in a K-State press release.

Native to Japan, China, Korea and the Primorsky Krai region of eastern Russia, the species has so far become well established in Australia, New Zealand and on several Pacific Islands. Female longhorned ticks can reproduce asexually-a rare trait that allows for rapid population spread-and the species can thrive under diverse climatic conditions.

Data from the CDC indicate that tickborne disease in humans is on the rise in the United States, with the reported prevalence increasing by nearly 20 percent between 2016 and 2017. Although the longhorned tick is currently considered largely a livestock pest (it has been implicated in the transmission of theileriosis to cattle), it has been known to parasitize humans as well, causing severe fever with thrombocytopenia syndrome as well as other diseases.

What would an invasion mean?

According to Stephen Barker, BSc, PhD, parasitologist and professor at the University of Queensland and a study coauthor, widespread invasion of H. longicornis in the United States “would carry a significant economic burden and potential human suffering, especially since this tick is capable of transmitting a variety of pathogens such as those cause Lyme disease and others.”

Dr. Raghavan and Steve Barker examine field-collected longhonred tick. Photo courtesy of Kansas State University

Tick migration is facilitated greatly by travel, with livestock, dogs and people all potential unwitting carriers. “We feel that there is a need for strict inspection and quarantine of cattle, other livestock and pet animals, particularly dogs, about to be transported from the current focus areas of this tick,” Dr. Raghavan says. “High levels of interstate movement of livestock and other animals occur each day. Cattle are moved slowly across the nation, stopping at multiple places-potentially dropping off female ticks. The movement of ticks via livestock and other domestic animals is not currently monitored or regulated, so it is only a matter of time, in our opinion, that this species will spread further in North America.”