Visual guide to help researchers track Asian longhorned tick

A shot of the Asian longhorned tick, a species that has recently invaded the United States. (Photo courtesy of James Gathany/CDC)Ever since the Asian longhorned tick (Haemaphysalis longicornis) was officially reported in New Jersey two years ago, researchers have sought to understand the threat this self-cloning species poses to human and animal health. Native to eastern Asia and Australia/New Zealand, where it transmits disease to both humans and livestock, H. longicornis has now been reported in multiple U.S. states: Arkansas, Connecticut, Delaware, Kentucky, Maryland, North Carolina, New Jersey, New York, Pennsylvania, Tennessee, Virginia and West Virginia.

Getting a handle on this tick species has been difficult so far, largely because it is nearly identical to the rabbit tick (Haemaphysalis leporispalustrisis) and the bird tick (Haemaphysalis chordeilis), both of which are mostly harmless to humans, according to Rutgers Today. To assist surveillance efforts, a collaborative research team, including members of the Rutgers Center for Vector Biology, has created a visual guide.

“To begin to understand the threat posed by Asian longhorned ticks in the U.S., we need to know the full extent of its distribution,” lead author of the guide Andrea Egizi, PhD, a visiting professor at Rutgers' Center for Vector Biology and a research scientist with the Monmouth County Tick-borne Disease Program, tells Rutgers Today. “We made this key so that researchers across the country have an easier way to identify [longhorned ticks].”

When these ticks actually got here

Thanks to the new guide, researchers now know that the Asian longhorn tick was actually spotted in the U.S. a lot earlier than previously believed. “… the Asian longhorned tick has been present in New Jersey since at least 2013, but that first discovery, found on a dog in Union County, was initially mistaken for a rabbit tick,” Dina Fonseca, PhD contributing author of the guide and director of the Rutgers Center for Vector Biology, told Rutgers Today.

The guide, published in ZooKeys, allows researchers to distinguish all life stages of the four Haemaphysalis species that may be encountered in North America. It specifically pinpoints their unique physical traits, such as hornlike spurs on the adult Asian longhorned tick's mouthparts. These characteristics are apparent on scanning electron microscopic images taken by the research team's collaborators.

“This tool will also help to improve our understanding of the biology and ecology of native Haemaphysalis species, which have been relatively poorly studied compared with other native ixodids,” the researchers say in the guide.

Although the Asian longhorned tick is largely considered a livestock pest, it can cause severe fever with thrombocytopenia syndrome as well as other diseases in humans, according to the Centers for Disease Control and Prevention. As of August 1, 2019, no harmful germs that can infect people have been found in the ticks collected in the United States, but research on this and other species is ongoing.  

“Careful monitoring to detect the potential arrival of other members of this genus is encouraged. Should additional Haemaphysalis species establish themselves in North America, this key will require revision,” the researchers conclude.