Brian P.D. Hannon: Invasive ticks in the Northeast
An Asian longhorned tick nymph, left, and an adult female.
— Centers for Disease Control and Prevention (CDC) photo
From ecoRI News (ecori.org)
This year’s tick season has brought an unwelcome development beyond the usual concerns about the disease-bearing arachnids with the confirmation of what one scientist said is a new invasive species in the Northeast.
The Asian longhorned tick, which poses a threat to livestock, was found in April to have moved to the Rhode Island mainland after an initial discovery on one of the state’s islands last year.
“This is truly an invasive species,” said Thomas Mather, a professor of public health entomology at the University of Rhode Island.
The ticks pose a risk to livestock because they attach themselves to various warm-blooded animals to feed. If too many attach to one animal, the loss of blood can kill the animal.
Mather said he found four Asian longhorned ticks about a month ago in South Kingstown while looking for the common blacklegged ticks known to bedevil outdoor enthusiasts and pet owners with the threat of Lyme disease and other infections transmitted through their bites as they hatch and grow to maturity in spring and summer.
Tick season is now in full swing .
“We’ve been seeing sporadic nymphs since April,” said Mather, noting these efficient carriers of disease will continue to spread as temperatures rise. “Somewhere around the week before Memorial Day they start to reach their peak numbers.”
The Rhode Island Department of Environmental Management (DEM) announced in late September that the Asian longhorned tick had been detected on Block Island, about nine miles off the mainland. But Mather’s recent discovery was the first on the state’s mainland and the presence of both nymphal and adult-stage ticks indicates that they have been present for at least one life cycle, he said.
Known by the scientific name Haemaphysalis longicornis, the Asian longhorned tick was first detected in the United States in 2017. As of early October 2020, the tick was known to be in Northeast states, including Rhode Island, Connecticut, Delaware, New York, New Jersey and Pennsylvania. Other states where the tick appears include Arkansas, Kentucky, Maryland, North Carolina, South Carolina, Ohio, Tennessee, Virginia and West Virginia, according to the U.S. Centers for Disease Control and Prevention (CDC).
Mather said the Asian longhorned tick differs in a few key ways from the blacklegged ticks, which are better known as deer ticks for their habit of using white-tailed deer as hosts.
The Asian longhorned tick can be found in batches of thousands in grass, shrubbery or on animals. But they don’t require the same high levels of humidity needed for survival by other tick varieties, Mather said.
“They don’t mind being out in the open” said Mather, noting that the arachnids can live in sunny areas beyond the moist lawn edges, fallen leaves or high grass areas normally targeted by homeowners or professional pest controllers applying insecticides.
Adult blacklegged tick (aka deer tick)
— CDC photo
Ticks feed on blood, with the blacklegged strain preferring white-tailed deer and white-footed mice, which are a primary source of tickborne Lyme disease. Up to 70 percent of white-footed mice in Rhode Island carry the Lyme bacterium Borrelia burgdorferi, Mather said.
The parasites transmit infections by exchanging blood with those they bite, whether animals or humans. The longer they remain attached, the more blood and germs they pass, making their quick removal paramount to avoiding Lyme disease, which causes headaches, fatigue, swollen lymph nodes, muscle and joint aches, fever and chills.
“It takes some time for the Lyme disease-causing bacteria to move from the tick to the host,” according to the CDC. “The longer the tick is attached, the greater the risk of acquiring disease from it.”
The first known instance of an Asian longhorned tick biting a person was in June 2018 in Yonkers, N.Y., which was reportedly confirmed by the CDC. As testing continues in the United States, “it is likely that some ticks will be found to contain germs that can be harmful to people. However, we do not yet know if and how often these ticks are able to pass these germs along to people and make them ill,” the CDC reported.
“This tick is a little weird. Happily, though, it doesn’t seem to like to bite people,” said Mather, who noted the Asian longhorned isn’t believed to be a Lyme disease carrier.
Deer ticks are among the most prevalent types in Northeast and Mid-Atlantic states, along with larger dog ticks, although only the former carry Lyme disease.
Ticks can also transfer anaplasmosis and babesiosis, blood infections with symptoms including fever, chills and sweats, fatigue and gastrointestinal ailments such as nausea and vomiting. One in four ticks in Rhode Island carry the germ causing Lyme disease, but Mather warned vaccination strategies focusing on Lyme prevention alone can cause a false sense of security and possibly result in the other infections being overlooked.
Climate change has no direct effect on ticks, because they are affected by humidity levels rather than temperature. Without enough humidity, ticks will dry up like a plant without enough water, but they can survive in varying climates.
“These ticks are in Duluth, Minnesota,and Florida,” Mather said. Yet he explained the changes in global climate can impact ticks – hurting or helping them – by altering the number of animals on which they feed. “The change that we’re finding is more related to the presence or absence of reproductive hosts.”)
Mather said Rhode Island also has experienced an increase in lone star ticks. Lone star ticks, which have moved northward in the United States for a decade, were previously only found off Rhode Island’s shore on Prudence Island, but now have infested Conanicut Island, Mather said.
A lone star tick
The lone star tick is a “very aggressive biter but it won’t carry or transmit the Lyme disease germ,” said Mather, who added there is still a danger of the parasites transmitting anaplasmosis and babesiosis.
Mather said lone star tick bites can also produce a red-meat allergy. Ticks taking in blood from an animal can ingest a specific sugar — galactose-α-1,3-galactose, also known as alpha-gal — found in red meat and then transfer the material to humans. The resulting symptoms, including rash, hives, nausea and difficulty breathing, can take hours to first appear and possibly months to fully develop, making the bite, rather than the existing allergy — referred to as Alpha-gal syndrome — appear to be the cause of the adverse reaction.
The University of Rhode Island’s TickEncounter website provides abundant information about the arachnids and the harmful infections they transmit, as well as tools for sharing tick locations, strategies to avoid bites and blog posts by experts.
People who plan to be in tick habitats should wear clothing treated with the tick-killing chemical permethrin and use tactics to prevent the insects from reaching skin such as tucking pant legs into socks. Daily tick checks are also important, especially in hiding spots including the backs of knees, inside armpits and around waistbands.
Regardless of the type of tick encountered, Mather echoed the CDC warning about removing the parasites as quickly as possible.
“The longer a tick is attached, the more likely it’s going to deliver an infectious dose,” he said.