- The Washington Times - Thursday, May 11, 2017

Black-legged and deer ticks have spread into new areas across the country, carrying Lyme disease into places where it didn’t exist 20 years, according to the federal Centers for Disease Control and Prevention.

The CDC estimates that about 30,000 U.S. residents are infected with Lyme disease each year, but notes that underreporting could put the actual count at 300,000 cases.

“Since the late 1990s, the number of reported cases of Lyme disease in the United States has tripled, and the number of counties in the northeastern and [upper-midwestern] United States that are considered high-risk for Lyme disease has increased by more than 300 percent,” research biologist Rebecca Eisen wrote on the CDC website.

“One explanation for this trend is that the ticks that can transmit Lyme disease have expanded their geographic range and are now being found in places they weren’t seen 20 years ago,” said Ms. Eisen, who works at the National Center for Emerging and Zoonotic Infectious Diseases, Bacterial Diseases Branch, Division of Vector-Borne Diseases. “This makes it more important than ever for people to take steps to prevent tick bites, particularly during the spring and summer when ticks are most active.”

The CDC says that 96 percent of cases occur in 14 states: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Virginia and Wisconsin — but instances of Lyme disease are expanding to Canada and even Europe.

Over the past few years, researchers have increased their understanding of Lyme disease, and are experimenting with ways to predict how severe tick season will be.

It starts with acorns.

“The bottom line, stated briefly, is that acorn mast [fruit of forest trees] affects tick populations in oak forests,” Howard Ginsberg of the U.S. Geological Survey told The Washington Times in an email. “While the acorns are not directly related to nymph ticks — the stage at which ticks contract the bacteria associated with Lyme’s disease — large numbers of acorns attract more deer and rodents, providing a suitable hosting environment for ticks to feed, grow, drop off and lay eggs that will affect the tick population the following year.”

Richard Ostfeld, a disease ecologist at the Cary Institute of Ecosystem Studies in Millbrook, New York, says the white-footed mouse is the most dangerous culprit in transferring to deer ticks the Borrelia burgdorferi bacteria, which causes Lyme disease.

“More acorns leads to more mice, leads to more infected ticks, leads to more Lyme disease in us,” Mr. Ostfeld said in a CBS New York interview earlier this month.

Areas where the predator population has decreased — such as foxes, bobcats and owls — allow the mice population to thrive and play host to nymph ticks, he said.

USGS’ Mr. Ginsberg and his colleagues are studying the differences between southern and northern ticks. Higher humidity and temperatures force southern ticks to protect themselves by hiding under loose foliage, robbing them of a chance to latch onto a passing human leg. Northern ticks readily attach themselves to passers-by because they hide in tall grass.

Ticks are very small, and the tell-tale sign of Lyme disease — a bull’s-eye rash — is not always apparent. Symptoms can include fever, headache and fatigue.

The disease is treated with antibiotics, but if left untreated for weeks or months, more serious complications can arise, such as infection and swelling in the joints, the heart and the nervous system, inflammation of the brain and spinal chord and problems with short-term memory.

No vaccine is available for humans, but there is one for pets, which should be checked frequently in case of carrying a tick into the home.

A less common but equally worrisome tick-borne illness is Powassan virus, or POW. There have been only 75 cases of POW in the last 10 years, but the CDC calls for extra vigilance to avoid a tick-borne infection.

A potentially fatal disease, POW can cause inflammation of the brain or the membranes surrounding the spinal chord.

“Symptoms can include fever, headache, vomiting, weakness, confusion, loss of coordination, speech difficulties, and seizures,” the CDC says on its website.

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