Annual Tick Season Includes Arrival of New Invasive Species
By BRIAN P. D. HANNON/ecoRI News staff
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| An Asian longhorned tick nymph, left, and an adult female. (CDC) |
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 will be in full swing as the nation marks Memorial Day on May 31.
“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 9 miles off shore. But
Mather’s recent discovery was the first on the state’s mainland and the
presence of both nymphal and adult-stage ticks indicates 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 northeastern 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 also known as deer ticks for their habit of using white-tailed
deer as hosts.
The
Asian longhorned tick is a parthenogenous strain, meaning females produce
without mating, and 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 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.
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| Blacklegged ticks carry Lyme disease. (CDC) |
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.”
An adult female lone star tick. (CDC). EDITOR'S NOTE: having
been bit by one of these little bastards, their bite is distinctive - stings
'like a hornet sting. At least that's how it felt to me - Will Collette
Mather said Rhode Island also has experienced an increase in lone star ticks, a variety raising some unnecessary anxiety for red-meat lovers.
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.
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.
Warnings about lone star tick bites producing a red-meat allergy are overblown, Mather said, explaining the reaction only occurs in a limited number of people, much like a peanut allergy.
Ticks taking in blood from an animal can ingest a
specific sugar found in red meat and then transfer the material to humans. The
resulting queasy stomach can take hours to first appear and possibly months to
fully develop, making the bite, rather than the existing allergy, appear to be
the cause of the adverse meat reaction.
“That’s
something people shouldn’t overreact to,” he said.
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 pantlegs 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.