For many years, the most notorious tick in Pennsylvania was the Blacklegged tick, also known as the deer tick, a parasite that can transmit Lyme Disease and Powassan virus.
But perhaps the Asian Longhorned tick will one day eclipse that tick in fame. Native to China and other countries in East Asia, the Longhorned tick has spread far and fast since it was first spotted here on a sheep farm in New Jersey in 2017.
Now it has shown up in at least twenty states, said Mike Bentley, an entomologist at the National Pest Management Association, a trade organization.
In just the past five years, the Longhorned tick has become the second-most common tick in Pennsylvania, according to recent reporting by WHYY.
An adult Longhorned tick is about the size of a sesame seed and its ‘mouth parts’, as scientists refer to them, are shaped like horns. A female Longhorned tick can reproduce without mating, considerably speeding up the process. Females can lay upward of 1000 eggs in a single spot, all of which will hatch around the same time.
“You have an area that is going to be very small that suddenly has 2000 tiny ticks crawling around,” said Bentley.
In general, ticks are “sit-and-wait parasites,” Bentley said. In a behavior called “questing,” they wait at the edges of twigs or blades of grass with their arms and legs hanging out until they detect a host. Then they grab on.
Then, as Bentley described their feeding process: they use their ‘special mouth parts’ to hook into skin, sucking human (or animal) blood while simultaneously regurgitating saliva into the wound. The saliva serves to numb the area — so the host doesn’t remove the tick — and also creates an anticoagulant to keep the blood meal flowing.
Longhorned ticks arrived in Ohio in 2021 in such high numbers that they exsanguinated three cows. (’Exsanguination’ means the act of draining blood from a person or animal until it dies). Researchers at Ohio State later estimated there were tens of thousands of ticks on each animal.
Longhorned ticks can feed off a wide variety of hosts, meaning their survival is “certainly not going to be limited by access to food,” Bentley said.
Because they were first introduced nearby, Pennsylvania is “definitely a little bit of a hotbed” for the invasive tick, said Payton Marie Phillips, a postdoctoral researcher at the University of Georgia.
Phillips was the lead author of a 2025 study examining what pathogents might be carried by Longhorned ticks in Southeastern Pennsylvania forests. Phillips and her fellow researchers dragged white cloth along the ground in Philadelphia and its collar counties and then tested the midlife ticks in a lab. Ultimately they didn’t find any of the five pathogens they tested for in the Pennsylvania brood.
Longhorned ticks elsewhere in the U.S. have tested positive for the causative agent of Lyme disease, according to new research published by the U.S. Centers for Disease Control and Prevention. But they don’t seem likely to be able to transmit it to humans, Phillips said, adding that they still may be able to transmit other diseases, including Rocky Mountain Spotted Fever and the Babesiosis, which destroys the body’s red blood cells and causes flulike symptoms.
As scientists continue to study the tick and learn more about its survival, Phillips and Bentley suggest residents do thorough tick checks after spending time outside in Pennsylvania.
“They’re easy to overlook. They’re easy to misidentify,” Bentley said. “A challenging tick all around.”
