8/7/18
Invasive new tick is spreading in the US
An invasive new tick is spreading in the US
https://www.wral.com/an-invasive-new-tick-is-spreading-in-the-u-s-/17750702
For the first time in 50 years, a new tick species has arrived in the United States — one that in its Asian home range carries fearsome diseases.The Asian long-horned tick, Haemaphysalis longicornis, is spreading rapidly along the Eastern Seaboard. It has been found in 7 states & in the heavily populated suburbs of New York City.
At the moment, public health experts say they're concerned, but not alarmed.
Although domestic U.S. ticks are a growing menace & transmit a dozen pathogens, no long-horned ticks here have yet been found with any human diseases. In Asia, however, the species carries a virus that kills 15% of its victims.
Known in Australia as bush ticks & in New Zealand as cattle ticks, long-horned ticks can multiply rapidly & suck so much blood from a young animal that it dies. The ticks bloat up like fat raisins until their tiny legs are barely able to support them.
After a blood meal, females can lay hundreds of fertile eggs without mating.
“One tick can crank out females in fairly large numbers,” said Thomas Yuill, a retired pathobiologist at the University of Wisconsin, Madison, who was one of the first to raise alarms about the invaders.
The first long-horned tick was found last summer in western New Jersey. This summer they were collected in public parks & a golf course in Bergen, Essex and Middlesex counties in New Jersey, & in wooded & grassy areas of New York’s Westchester County.
They were reported in Pennsylvania for the first time last week, & have been sighted in Arkansas, North Carolina, Virginia & West Virginia.
They were found feeding on horses, dogs, deer, a calf, a sheep & an opossum. They do bite humans, but it isn't clear how often.
People should use the same precautions they do against domestic ticks, experts said, such as using repellents & checking for ticks after walking through woods or tall grass.
Tadhgh Rainey, an entomologist at the public health department of Hunterdon County, New Jersey, found the first long-horned ticks in the country last August, when a woman who'd been shearing her pet Icelandic sheep came to his department with ticks on her hands and wrists.
“I thought she’d have a few,” Rainey said in an interview. “But she was covered in them, easily over 1,000 on her pants alone.”
Most were young nymphs about the size of dust specks. “She had a change of clothes in her car, so we put her clothes in the freezer to kill them,” Rainey recalled.
The ticks didn’t match any North American pests, & initially he couldn't identify them. The woman’s 12-year-old sheep was penned alone & had never traveled, so where they came from remained a mystery.
A month later the woman called again to see if he'd figured out what they were, & Rainey drove out to see the animal for himself. “A minute after we entered the paddock, even before I touched the sheep, I was covered in ticks,” he said.
The sheep was weak from blood loss, so he gave the owner some insecticidal livestock wash. The grass around the paddock was later cut & the area sprayed in an effort to eliminate the outbreak.
Andrea Egizi, an entomologist at Rutgers University, finally identified the longhorns by DNA analysis. Her lab has now tested more than 100 specimens found in New York & New Jersey.
Thus far, Egizi said, none have any of the pathogens causing the 6 diseases she screens for: Lyme disease, relapsing fever, babesiosis, anaplasmosis & 2 varieties of erlichiosis.
The Centers for Disease Control & Prevention lab in Fort Collins, Colorado, has screened about 100 long-horned ticks for 3 dangerous viruses — Powassan, Heartland & Bourbon — & all came up negative, said Ben Beard, the agency’s deputy director of vector-borne diseases.
The lab now has 10 live longhorns & is feeding them to create a colony, Beard said. That will take about a year, & then researchers can determine whether they can transmit Rocky Mountain spotted fever & other diseases.
In East Asia, long-horned ticks do carry pathogens related to Lyme & others found in North America. But the biggest threat is a phlebovirus that causes SFTS, for severe fever with thrombocytopenia syndrome. (Thrombocytopenia means abnormally low levels of platelets, which help the blood clot; a severe drop triggers internal bleeding and organ failure.)
The syndrome has an overall fatality rate of about 15%, said Terry A. Klein, an entomologist working with the U.S. military in South Korea. But SFTS is more lethal to people aged 60 or older, killing half of them.
However, the syndrome isn't found in Australia or New Zealand, earlier stops for the long-horned ticks as they spread from Asia. In those countries, they cause babesiosis & theileriosis in cattle but are mostly “of nuisance value” to humans, said Dr. David Thomson, a veterinarian in Queensland, Australia.
It’s not clear that the SFTS virus, which is related to the Heartland virus found in a number of U.S. states, could get established in this country, because its transmission cycle is unknown — it may need more than one host.
It’s not known when or how long-horned ticks reached the United States, nor why the species is spreading so fast now. They bite birds, but Rainey said he suspected they originally arrived on a large animal. As far back as 1960, he said, the ticks were found on a horse held in quarantine.
One collected in 2013, Beard said, was misidentified until recently as a rabbit tick, which is also in the Haemaphysalis genus.
In theory, just one female could have produced all the long-horned ticks spreading in the country through asexual reproduction. But Egizi said she has found 3 mitochondrial DNA lineages, meaning at least 3 females arrived.
Although experts said having a new invader is unsettling, they worry more about deer ticks, lone star ticks & other established species whose ranges are growing as winters get warmer.
Cases of the illnesses they transmit — everything from Lyme disease to alpha-gal, an allergy to red meat — are increasing rapidly. Even in Asia, only about 1% of long-horned ticks have the SFTS virus; in parts of this country, 25% of deer ticks carry Lyme disease.
“The jury’s still out on how big a threat this is,” Beard said. “But we think it’s a very important question to address.”
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