This tick species is a major livestock pest in Australia, New Zealand, Japan, and several Pacific islands — and now has been spotted in the US.
The tick is called the longhorned or bush tick, and its scientific name is Haemaphysalis longicornis. It is native to China, Japan, and Korea, and it's an invasive species and a major livestock pest in Australia and New Zealand.
Hundreds of the arachnids can attach themselves to a single animal, and in rare cases can consume so much blood it causes anemia or even fatalities in cattle, which is called exsanguination.
The ticks were first seen in the United States in New Jersey on Aug. 1, 2017, when a woman reported to the Hunterdon County Department of Health that her pet sheep was covered in hundreds, maybe thousands of the ticks. The woman, who first noticed them when she was shearing her sheep, also had the ticks on her clothing.
The sheep's paddock was so infested with ticks that they crawled on the health investigators' pants as soon as they stepped inside. The good news is that the woman was not bitten by the ticks, nor were the health investigators, James Occi, an entomologist at the Center for Vector Biology at Rutgers University in New Brunswick, New Jersey, told BuzzFeed News.
They treated the sheep and the paddock with the insecticide permethrin during several visits, and both were eventually tick-free. Experts had trouble identifying the species, and in November determined it was Haemaphysalis longicornis.
It was hoped that the species would not be able to survive the cold winter. But when Rutgers and the health department went back to the farm in April, "we found some live specimens," Occi said.
Experts are not really sure how the ticks got into the US, or where the sheep came into contact with them.
The 12-year-old Icelandic sheep was the only domestic animal on the property and it had never been outside the US. Although the ticks haven't been seen in the US before, they occasionally have been found on and removed from animals coming into the US, including horses.
The ticks were also found in a second location in Union County, New Jersey. Those ticks had been collected from grass in the Watchung Reservation, a nature preserve, in May 2017, but weren't positively identified to be the non-native species until relatively recently, Andrea Egizi, a research scientist for the Monmouth County Tick-borne Disease Lab and a visiting professor at the Rutgers Department of Entomology in New Brunswick, told BuzzFeed News.
So far, the ticks that have been tested (and the sheep itself) have been negative for disease-causing pathogens, she said, but tests are ongoing.
"There are a lot more samples now and we are working on doing the pathogen testing on the wider numbers of samples, but we haven’t completed that yet," Egizi said.
Tick experts say although the appearance of the species is concerning, it's not alarming.
The ticks are known to be carriers of diseases in other countries, mostly ones that affect livestock. in South Korea, Japan, and China, they have been known to transmit a newly emerging virus that causes a rare condition called severe fever with thrombocytopenia syndrome.
"There’s no indication that that’s going to happen here," Occi said. There have been only a handful of cases in those countries, "mostly in rural and farming areas; it’s not like you are going to find it in your backyard or garden," he said.
The ticks do have one unique characteristic — they can reproduce asexually. In a process called parthenogenesis, no males are necessary for the ticks to lay and hatch eggs. Of the more than 200 ticks collected from the sheep and over 900 collected nearby, only one was male, according to the study the investigators published in the Journal of Medical Entomology.
"I think it’s certainly something that we should watch, especially because this tick is a little bit different from some in that it has the ability of what we call parthenogenesis," said Thomas Mather, professor of public health entomology and director of the University of Rhode Island TickEncounter Resource Center.
He said exsanguination of farm animals was unlikely and that the ticks may not spread to other areas. In fact, it's possible they have been in the US for years without anyone knowing.
However, it can be hard to predict what will happen with an introduced species. "I think the biggest concern is whenever you put a species into a new situation, who knows what it's going to be able to do in the new situation?" he said. "That’s really the concern."
As adults, the longhorned or bush ticks can be about the size of a pea when engorged with blood.
The two other life stages of the tick — nymph and larvae — can be so small they are hard to see with the naked eye. The ticks are brown and bigger than the black-legged or deer ticks that carry Lyme disease in the US, but smaller than dog ticks, Egizi said.
"This is kind of just another tick," she said. "At this point I think people should be far more concerned about native species." New Jersey has more than 4,000 cases of Lyme disease each year — about 13% of all cases in the US — and it's transmitted by native tick species that are much more common than this one.
"The good news is that if you protect yourself from the native species you will also be protecting yourself potentially from this exotic species, so the same kind of prevention methods – wearing long pants, using repellent, and performing tick checks – all of that stuff will help you regardless of what kind of tick is out there," she said.
"Don’t just worry about this tick; you should be worried about ticks in general," said Occi. "If you know there are ticks in the area, or you suspect there are ticks in the area, just use the proper precautions. Stay on the trail, don’t walk in the woods, use insect repellant, and do a proper tick check when you get home."