A new invasive tick species capable of transmitting several severe diseases is spreading in the United States, posing an emerging threat to human and animal health, according to a pair of reports issued Thursday.
In August of last year, it was discovered on a 12-year-old pet Icelandic sheep in western New Jersey. Since then, the tick has been found in Arkansas, Connecticut, Maryland, New York, North Carolina, Pennsylvania, Virginia and West Virginia. The species has been found on pets, livestock, wildlife and people. So far, though, there is no evidence that the tick has spread pathogens to humans, domestic animals or wildlife in the United States, according to a report from the Centers for Disease Control and Prevention.
But public health officials are worried about the potential for Haemaphysalis longicornis to spread disease. In other parts of the world, it is a major livestock pest; its bites can make people and animals seriously ill. In some parts of Australia and New Zealand, the ticks can suck so much blood from dairy cattle that they cause milk production to drop by 25 percent, researchers have found.
In Asia, the tick carries a newfound virus that causes human hemorrhagic fever and kills up to 30 percent of its victims. In 2013, South Korea reported 36 cases, 17 of whom died. Although that virus is not in the United States, it is closely related to the Heartland virus, another life-threatening tick-borne disease that circulates in the United States. Health officials are particularly concerned about the tick’s ability to adapt to be a vector for that virus and other tick-borne illnesses in the United States.
The tick “is potentially capable of spreading a large number of diseases,” said Lyle Petersen, director of the CDC’s Division of Vector-Borne Diseases. “We really don’t know if diseases will be spread by this tick in the United States and, if so, to what extent. But it’s very important that we figure this out quickly.”
In contrast to most tick species, a single female tick can produce up to 2,000 eggs at a time without mating. As a result, hundreds to thousands of ticks can be found on a single animal, person, or in the environment.
Illnesses from mosquito, tick and flea bites more than tripled in the United States from 2004 to 2016, according to the CDC. The increase in these vector-borne diseases has many underlying causes: expanding travel and trade, urbanization, population growth, and increasing temperatures.
Warming temperatures and climate change make the environment more hospitable to ticks or mosquitoes that spread pathogens and increase the length of the season when ticks are active, Petersen said.
Next week, officials from several federal agencies — including the CDC, the Agriculture Department, the Environmental Protection Agency, the National Park Service and the Defense Department — are meeting to develop a national coordinated strategy for fighting these vector-borne diseases.
“The problems are getting worse and worse,” Petersen said, noting that every state except Alaska is grappling with a rise in these diseases. “We’re losing this battle.”
Officials said they are trying to raise awareness among public health officials, health-care professionals and veterinarians about the potential threat from this species. In addition to the CDC report, Petersen and CDC colleagues published a companion paper in the American Journal of Tropical Medicine and Hygiene highlighting the “considerable gaps” in the ability of public health systems to respond to these diseases.
Many diseases spread by ticks are underreported. There are also no proven measures that can be scaled up to control many vector-borne diseases that are transmitted by the black-legged or deer tick that spreads at least seven human pathogens in the United States, including the bacteria that causes Lyme disease.
Officials don’t know when or how long the longhorned tick arrived in the United States. Between August 2017 and September 2018, there have been 53 reports of the tick in the United States. The states with the highest percentage of infested counties are New Jersey (33 percent), West Virginia (20 percent) and Virginia (12 percent), including Fairfax County, a D.C. suburb. Using retrospective analysis, scientists believe the invasion occurred years earlier.
Tadhgh Rainey, an entomologist at the Hunterdon County Division of Health in New Jersey, discovered the ticks Aug. 1, 2017, when a woman who had been shearing her pet Icelandic sheep arrived at the department with what she thought were mites on her hands.
Upon closer inspection, they turned out to be larval ticks. And she was covered in them.
“She had them all over her clothing. We’re talking over 1,000 ticks on her body,” Rainey recalled in an interview. “They were a species I had never seen before.” Rainey’s assistant provided a change of clothes for the woman, and health officials put her pants in a freezer to kill the ticks.
As Rainey sought to identify the species, the woman returned about two weeks later, this time with engorged adult ticks from her sheep. Rainey said he realized it was nothing he had ever seen before and went to visit her farm to see the animal for himself.
“I got covered in ticks,” he said. “They were embedded all over the sheep, thousands of them on the ears, too many to count.”
Andrea Egizi, a research scientist at the Monmouth County Tick-Borne Disease Laboratory at Rutgers University, identified the tick using DNA analysis, and its identity was later confirmed by USDA scientists.
Rainey said the tick probably came to the United States on a large animal. That part of the state has an active horse and sheep trade overseas. The affected sheep had never traveled outside the country. “Or it could have come over on a person who went on a nature hike in New Zealand,” he said.
Health department officials were able to kill all the ticks on the sheep and eliminate them on the woman’s property. The sheep, named Hannah, died recently from old age, Rainey said. The health department has the woman’s trousers because “she still doesn’t want her pants.”