Spring Break
Professor hypothesizes level of humidity predictor for ticks
Jeff Sullivan
Issue date: 11/7/08 Section: News
|
Mather said while URI's more rural campuses are not at high risk for tick encounters, he did point out that South County has one of the highest rates of tick bites in the country.
"Our working hypothesis right now is that tick activity is really dependent a critical [on a] threshold of relative humidity," Mather said. "We did an experiment in the laboratory and it conclusively showed ... they just can't stand low humidity."
In 2006 alone, he said, his vector-borne disease center estimated more than 700,000 people in Rhode Island were at risk of encountering a deer tick where they live.
Mather said he and his researchers have observed that deer ticks are evolved to withstand humidity below 85 percent for about eight hours, and any time after that they usually die.
This hypothesis was first tested in the laboratory and then later in nature. Mather had a graduate student use specialized equipment to collect humidity data hourly in 18 different locations during the course of two years, which confirmed the results of the lab experiment.
The averages of the data showed 10 a.m. to 6 p.m. were the hours where the relative humidity was usually less than 85 percent.
"Eighty-five percent and eight hours seems to be the critical threshold," he said.
Mather cited this year as an example, although he said not all the data has come in yet. This year, he said, Rhode Island experienced two or three consecutive days early in May that read less than 85 percent relative humidity during the entire three-day period. This year he said deer tick numbers are much lower than previous years, and he attributes this to the low humidity early in the season.
"That may have been enough to become detrimental to some of these nymph ticks [baby ticks], just at the time of year when they were coming out," Mather said. "So we may have lost a slug of them, and once you lose them, it's not like they come back."
