First Report of East Asian Tick Species in the United States

A recent study has described the first documentation of the east Asian tick Haemaphysalis longicornis in the United States, on a sheep in Hunterdon County, New Jersey.

Tadhgh Rainey, MS, the division head of the Hunterdon County Division of Health, Flemington, New Jersey, and colleagues published the results of their study online February 19, 2018, in the Journal of Medical Entomology.

“This is the first description of multiple life stages of H. longicornis infesting an animal within the United States, although single specimens have been occasionally intercepted at quarantine stations, including a single specimen on a horse at a quarantine station in Clifton, NJ in 1969,” the authors write.

Also known as the cattle tick, longhorned tick, or bush tick, H. longicornis is native to East Asia. Until now, H. longicornis had not been found on an unquarantined animal in the United States, but it is known to be a major invasive pest in other regions of the world—namely New Zealand, parts of Australia, and some of the Pacific islands. Cases of H. longicornis infestation in individuals have also been reported in these regions, as well as in Russia and South Korea.

This tick species has been described as self-cloning because it reproduces asexually by parthenogenesis, allowing it to multiply quickly. Although it feeds on the blood of various mammals, H. longicornis is best known as a pest of livestock. In particular, heavy infestations of this tick in cattle can lead to weakness, and, in extreme cases, exsanguination and death.

In New Zealand, H. longicornis is the main vector for Theileria orientalis (Ikeda). This blood-borne theilerian parasite causes Theileria-associated bovine anemia and was first identified in beef cattle and dairy cattle in New Zealand in 2012.

In East Asia, H. longicornis has also been linked to the spread of a newly-described phlebovirus that causes Severe Fever with Thrombocytopenia Syndrome (SFTS). This emerging hemorrhagic fever is associated with a wide spectrum of clinical signs and symptoms, including fever, thrombocytopenia, and leukocytopenia, with a case fatality rate of between 12% and 30%.

In this case in New Jersey, a sheep owner took samples of ticks from her 12-year-old Icelandic sheep to the Hunterdon County Health Department in August 2017. The sheep was infested by hundreds of ticks, including all 3 active life stages (larva, nymph, adult). The ticks were present all over the sheep’s body but were concentrated on the ears and face.

According to the owner, the sheep had no history of travel outside the United States.

Researchers identified the ticks as belonging to the genus Haemaphysalis but found that the specimens were not consistent with any of the species of Haemaphysalis that are native to the Western Hemisphere. Indeed, further analysis identified the ticks as Haemaphysalis longicornis.

The owner treated the sheep using a permethrin wash in late September, and the animal was found to be free of ticks at follow-up examinations in early and late November.

“It is currently unknown whether the New Jersey collections represent a limited or established population, but because this species could present a significant threat to human and animal health in the United States, vigilance is encouraged,” the authors conclude.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.

Feature Picture Source: Patrick O' Sulivan / flickr / Creative Commons .