An invasive tick species was found to have spread to an eighth state Tuesday, when the Maryland Department of Natural Resources announced one was found on a deer in Washington County, The Washington Post reported.
The tick, known as the Asian long-horned tick, scientific name Haemaphysalis longicornis, is the first new tick species to enter the U.S. in 50 years, The New York Times reported Monday.
In Asia, the species carries a disease that kills 15 percent of those infected, but no human diseases have been linked to the species in the U.S. since it was first found in New Jersey last August.
Since then, it has spread to New York, Arkansas, North Carolina, West Virginia, Virginia and, most recently, Pennsylvania and Maryland.
"The discovery of the longhorn tick is another reminder of the importance of tick prevention for Pennsylvanians," Secretary of Health Dr. Rachel Levine said in the July 31 announcement that the ticks had been found in that state. "Ticks can be found in your own backyard, so it is essential to wear long sleeves and pants, use insect repellant containing DEET to help keep you safe from ticks and the diseases they carry. It is also important to check yourself and your pets for ticks, as pets can bring ticks indoors."
The Asian long-horned ticks have two distinctive characteristics, Live Science reported. First, females can reproduce asexually, laying as many as 2,000 eggs after feeding, according to the Pennsylvania Department of Health, which is enough to start a new population wherever they hatch, the U.S. Department of Agriculture says.
Second, the ticks' large numbers mean they can suck livestock to the point of anemia, or even death.
The incident that led to the discovery of the ticks on U.S. soil bore out both of those facts.
A New Jersey woman who had been shearing her sheep came into the public health department of Hunterdon County with ticks, mostly nymphs, on her arms and legs, entomologist Tadhgh Rainey told The New York Times.
"I thought she'd have a few," Rainey said. "But she was covered in them, easily over 1,000 on her pants alone."
When Rainey drove to inspect the sheep a month later, he noticed the animal was weak from the loss of blood.
The ticks were finally correctly identified by Rutgers University entomologist Andrea Egizi, who has since tested more than 100 found in New York and New Jersey.
Egizi has screened the ticks for Lyme disease, relapsing fever, babesiosis, anaplasmosis and two varieties of erlichiosis, and none have been infected.
The Center for Disease Control has likewise tested specimens for the Powassan, Heartland and Bourbon viruses and not had any positive results.
In Asia, the ticks do spread diseases. The most dangerous is called S.F.T.S., for severe fever with thrombocytopenia syndrome, which causes blood to thin so much that it leads to internal bleeding and organ failure.
But S.F.T.S. has not spread to New Zealand and Australia, where the ticks have also been found, and health experts are currently more worried about the spread of known-disease-carrying pests like deer ticks and lone star ticks as warmer winters expand their ranges.
It is still unknown how the long-horn ticks first arrived in the U.S. The sheep patient zero had never traveled and was not kept with other animals.