New Invasive Tick Species Discovered in U.S. Has Experts Concerned

Health experts are warning the public about a rare type of tick that was recently discovered in the United States.

The species, called Haemaphysalis longicornis, typically resides in East Asia but last summer a number of the strange-looking parasites were found on a sheep living in Hunterdon County, New Jersey. According to a report published Monday in the Journal of Medical Entomology, the sheep had never traveled outside of the U.S. nor had it traveled locally in years, which has left experts confused as to how the ticks ended up there.

Related: Lyme disease isn't the only tick-borne illness that poses a threat in the U.S.

"It's possible it hitchhiked in on a different animal, but there were no other domestic animals on the property where it was found, so it would still have had to make its way from somewhere else without being detected in the original location," Andrea Egizi, senior author and research scientist at the Tick-Borne Disease Laboratory at Rutgers University, told Entomology Today. "It's a puzzle, and I'm not sure we'll ever know."

Although no cases of disease have been reported yet in New Jersey, the exotic species is known to transmit theileriosis, a disease that causes anaemia and can at times be fatal, among livestock. The disease has also been recorded in humans; however, that's far less common, Egizi said.

Among the nearly 900 tick species in the world, H. longicornis is one of only two species that's able to reproduce asexually. This is troubling because that means it can quickly reproduce since finding a mate isn't necessary.

Related: Nine-year-old found in pool of own blood dies from tick-borne virus

When investigators took a look around the area where the sheep were kept, there were so many ticks that they immediately crawled on their pants upon entering the paddock. Hundreds of ticks of all stages of life—larva, nymph, adult—covered the Icelandic sheep's body, a majority of which were found on its ears and face, according to the report.

"Ultimately there is great concern about the potential for an H. longicornis infestation in NJ, and this is being actively investigated, although the issue will likely not be settled before the spring (March-April) of 2018, when any surviving ticks would exit diapause and begin host seeking," Egizi and her colleagues wrote in the report.

In the meantime, they suggest people to be cautious because "suitable hosts and habitats are common and widespread [in the United States]," even if the tick itself hasn't established itself.