“Exceptional Crisis for public health”

URI researcher alarmed by another record-breaking year for ticks in Rhode Island

Todd McLeish, URI, 401-874-7892

Thomas Mather says tick situation is exceptional crisis for public health 

KINGSTON, R.I. – September 5, 2013 – University of Rhode Island tick expert Thomas Mather has been collecting data on deer tick abundance in Rhode Island for 20 years, but this is the first year he has linked the words “exceptional” and “crisis” together to describe the increased threat posed by ticks.

For the second year in a row, Mather and his team of researchers have found record numbers of nymphal blacklegged ticks at the 60 sites they monitor every summer. And now scientists believe there are as many as six different disease pathogens that can be transmitted by the poppy seed-sized ticks.

“The numbers of ticks we’re finding is shocking. There is no question that this level of ticks poses a significant threat to public health in Rhode Island,” said Mather, professor of entomology and director of the URI Center for Vector-Borne Disease. “Our sampling indicates that in those habitats even marginally appropriate for deer ticks, there is nowhere in Rhode Island that doesn’t likely have some, and many places have exceptional numbers.”

Mather describes deer tick habitat generally as somewhat shaded, wooded or brush-covered, including lawn edges with leaf litter.

These newest tick results follow on the heels of a recent pronouncement by The Centers for Disease Control saying that, based on preliminary analysis of studies designed to get a more accurate estimate of disease burdens, there are likely 300,000 cases of Lyme disease in the United States each year. Currently, the CDC only records about 30,000 Lyme disease cases annually. Deer ticks – also called blacklegged ticks – transmit the agents causing Lyme, babesiosis, anaplasmosis, and three newly recognized tick-borne disease threats: a relapsing fever borrelia, a deer tick virus, and an ehrlichia (a type of bacteria). All start with flu-like symptoms. Mather’s team has only found one (the relapsing fever borrelia) of these latter three germs in Rhode Island ticks, so far. Lyme, babesia and anaplasma are relatively common infections in Rhode Island deer ticks.

Mather said that Rhode Island had a second consecutive year of record-breaking tick abundance because “we’ve experienced really permissive conditions for these ticks.” Besides the new survey findings, his team’s recent research correlated high deer tick numbers in those years when humidity is high throughout the month of June.

“Nymphal ticks come out in late May, and if they experience adverse conditions early – bouts of low humidity in June – then some portion of them are killed off and aren’t around to bite people,” Mather explained. When humidity levels in the leaf litter habitat that these ticks hide in drops below 82 percent for eight hours or more, the ticks begin to dry up and die. “The more tick averse moisture events we have in June, the fewer ticks we’ll have.” 

Results of Mather’s 14 year retrospective study were presented at the International Lyme Borreliosis Conference recently held in Boston.

Other factors may play a role in determining blacklegged tick abundance and the threat of disease transmission. For example, although nymphal tick numbers were high in 2012, the crop of last fall’s adult stage blacklegged ticks was lower than expected. Mather believes that last summer’s high humidity but lower than typical population levels of chipmunks and mice for the nymphs to feed upon resulted in more ticks looking for a blood meal but fewer advancing on to the adult stage . This year, however, the chipmunk and mouse population is healthy, so the ticks probably have had more success finding a meal.

“That means we should expect a bumper crop of adult deer ticks this fall,” he said. “And they won’t go away after a frost.”

Despite his frequent pronouncements about the risk of being bitten by ticks in Rhode Island, Mather said that the “tick literacy level” in the region is still quite low, leaving a majority of residents ill-prepared to take appropriate measures to prevent tick bites. While nearly everyone believes they know something about ticks, Mather said there are five simple steps that all Rhode Islanders can take to dramatically reduce their risk of contracting any of the diseases transmitted by ticks.

1. Wear tick repellent clothing when going outside in tick habitat. Any clothing can be treated with the repellent permethrin, and it will repel ticks for as many as 70 washings. “Your clothes are the first place ticks make contact with you,” Mather said, “so treating your clothes with permethrin is an important first step.” Insect repellents containing DEET are not as effective against ticks.

2. Perform comprehensive daily tick checks of your body, especially below the belt where tiny ticks are easy to miss.

3. Know what kind of ticks are active in your area and how to identify them. “If you find a tick on yourself or your pet, don’t just throw it away,” said Mather. “Different ticks transmit different germs, so knowing what kind of tick bit you can help diagnose an illness that may develop.”

4. Treat your yard with tick-killing insecticides. The single most effective way to reduce deer ticks in your yard is by insecticide applications applied to the yard perimeter, shady perennial beds or along trails and paths in woods.

5. Protect your pets by using products that rapidly kill or repel ticks. Not only do you want to keep your pets healthy, but dogs and cats that roam in tick areas can be a risk to your family by bringing ticks to you when you least expect it. Mather said that Seresto pet collars are an effective new product that don’t require monthly treatments; there are a number of topical spot-on products that also work well as long as they’re applied monthly.

For more information about ticks and how to avoid being bitten, visit the University of Rhode Island’s TickEncounter Resource Center website at http://www.tickencounter.org.