URI entomologist finding ‘more ticks in more places’ this year

Posted on
Deer tick numbers up 52% over last year, likely to remain high into July

KINGSTON, R.I. – June 24, 2011 – As children celebrate the end of the school year and prepare to spend the summer outdoors, their parents should heed a warning from a University of Rhode Island entomologist: deer tick numbers in the state are well above average in 2011, and that means the risk of contracting Lyme disease or other tick-borne diseases is especially high.

Thomas Mather, director of the URI Center for Vector-Borne Disease, said he is seeing “more ticks in more places” this year. The abundance of deer tick nymphs is up 52 percent over 2010 numbers, 37 percent above the average of the last five years, and 15 percent above 2009, which was what Mather called “a very ticky year.”

Mather attributes part of the tick abundance this year to snow cover that lasted the entire winter and protected adult ticks from harm. While most of the adult deer ticks have disappeared by now, their disease-carrying offspring are just now reaching the peak of their seasonal abundance.

“We always start the late springtime with about the same number of nymphs each year,” Mather explained, “but the seasonal tick encounter risk is really just a function of how quickly nature kills them off.”

Deer ticks are very susceptible to drying out. When humidity levels in tick habitat drop below 80 percent for more than eight hours, the ticks are unable to rehydrate themselves and they die. Thus far, humidity levels in Rhode Island for May and June have not dropped below that threshold for any extended period, which is enabling these ticks to remain active and abundant.

“Another concern this year was that we were finding more and more of the adult stage deer ticks in places that we’re not used to finding them, like along suburban roadsides. And if adult ticks are there, nymphs are there, too,” Mather said. “Deer ticks are not just found in the deep woods, so Rhode Islanders need to be vigilant about checking themselves for ticks even if they don’t think they have entered tick habitat.”

What does the future hold for tick numbers this summer?

“It all depends on the humidity,” said Mather. “Preliminary findings from ongoing research in our labs suggest that the humidity conditions of two weeks ago can predict the likely nymphal tick encounter risk today, so when we start to have more extended periods of low humidity, tick numbers will decline soon after.”

Because of the current alarmingly high level of tick encounter risk, Mather recommends that all Rhode Islanders make an extra effort now to take appropriate action for avoiding tick bites and preventing Lyme disease by practicing personal protective measures daily and implementing tick control strategies around the yard. He recommends:

– checking your body thoroughly every day for ticks;

– using a fine-pointed tick removal tweezer to safely remove attached ticks;

– treating clothing with a repellent containing Permethrin and wearing the treated clothing whenever going in areas where ticks may lurk;

– keeping the edge of the yard clear of leaf litter because that’s where exposure to ticks is most likely to occur; and

– hiring a trained professional pest controller or arborist to apply an appropriate tick treatment around the yard.

“Most people won’t find the poppy seed-sized nymphal deer tick until it’s been attached for more than a day, and typically, about one-in-five nymphal deer ticks carry the Lyme disease bacteria and transmit it when they bite,” explained Mather. “That’s why wearing tick repellent clothing is such a good idea.”

Permethrin-treated clothing can go through several wash cycles and still be effective, depending on how the treatment is applied. For example, commercially treated clothes available from several vendors can be washed 70 times and are still repellent to ticks.

For more information about ticks, Lyme disease, and strategies for avoiding tick bites, visit www.tickencounter.org.