Invasive tick finds foothold in New Jersey

Late last year, federal authorities announced the presence of an exotic East Asian tick species on a New Jersey sheep farm. The New Jersey Department of Agriculture now has confirmed that Haemophysalis longicornis — also known as the longhorned tick — has successfully overwintered and possibly has become established in the state.

The longhorned tick, native to China, is a major invasive cattle pest in New Zealand, Australia, and several Pacific Island nations. The ticks swarm, causing heavy infestations that can drain infected livestock of their blood. They’ve also been shown to transmit tick-borne diseases to animals and humans.

Longhorned ticks had not previously been found in the United States outside of agricultural quarantine stations. Last August, a farmer in Hunterdon County, in western New Jersey, found the ticks while shearing sheep. Hundreds had collected around the face and beneath the thick fur of one 12-year-old Icelandic sheep. The ticks were so numerous in the one-acre paddock that they swarmed on the farmer’s pants legs.

How, and when, the exotic tick got to New Jersey remains a mystery. The infected sheep had never traveled outside the country and hadn’t been moved locally in many years.

“We were completely shocked to find it living here,” says Andrea Egizi, an adjunct professor at the Rutgers University Center for Vector Biology. Egizi, who runs a tick DNA-testing laboratory for Monmouth County, New Jersey, tentatively identified Haemophysalis longicornis using a DNA barcoding technique. The National Veterinary Services Laboratory, a branch of the USDA, confirmed the results in November.

Both the sheep and the field were treated with insecticides. A late November sweep of the property found no sign of them, but investigators couldn’t say for sure whether the treatment had killed the ticks or whether they had just gone into their overwintering phase underground.

When Egizi and a Rutgers colleague visited the property this spring, they once again found live longhorned ticks. A major concern now, says Egizi, is the spread of the tick to local wildlife.

In addition to livestock, the longhorned tick is known to parasitize deer and rabbits — frequent visitors to the suburban backyards that flank the sheep farm. “From there it could spread throughout the state and to livestock in other parts of the country,” she says.

The New Jersey Department of Environmental Protection, the USDA, and the Southern Cooperative Wildlife Disease Study have studies underway to determine whether the tick has already parasitized nearby wildlife. So far, there’s no evidence it has.

However, on April 25, the New Jersey Department of Agriculture announced that the longhorned tick had been found at a second location — an open area at a nature preserve in Union County, New Jersey, part of the New York City metropolitan area. The tick in question had been collected as part of an ongoing tick study in May of 2017, suggesting that the exotic species may have a longer history in the state than was previously suspected.

“With the finding of a tick on a second location, the possibility of having an established population increased,” wrote New Jersey state veterinarian Manoel Tamassia in an email to Ag Insider.

Initial laboratory work on the longhorned ticks collected in New Jersey doesn’t indicate that any were transmitting disease, though there’s concern that they could become a vector of tick-borne diseases in the future, according to Tamassia.

The new findings do not require management changes for livestock or pet owners already practicing tick control. For livestock, that typically means an insecticidal spray or wash, while pets often receive an oral or topical tick preventive. “The current prevention methods being used to control other ticks should also be effective against this species,” Tamassia says.

Lindsey Konkel is a New Jersey–based freelancer who reports on science, health, and the environment.