2012-09-27 / Front Page

Scientist expects outbreak of deer ticks in Jamestown

Surveillance shows 108 percent increase this year
BY KEN SHANE

According to a prominent scientist at the University of Rhode Island, Jamestown can expect a veritable explosion of deer ticks this fall. Dr. Tom Mather is the director of the Tick Encounter Resource Center, and a professor of public health and entomology at URI. Mather based his opinion on the large number of nymphal ticks that he found this summer, which will grow into adults this fall.

“Deer ticks come in larvae, nymphal and adults,” Mather said. “Each of those stages come at a different time of the year. This is our 19th year of a statewide surveillance of nymphal deer ticks in the summer. We have that as a quantifiable baseline. Most cases of Lyme disease are transmitted by nymphs because they’re tiny and people don’t see them.”

Mather said that when there is an up year for nymphal ticks, there is an increase in the occurrence of Lyme disease. It is not possible at this point to predict which years will see an increased number of nymphs.

“This past summer the nymphal surveillance that we do statewide showed a 108 percent increase over 2011,” Mather said. “And a 102 percent increase over the fiveyear average.” There are two surveillance sites in Jamestown.

The state health department no longer has a systematic system of tracking cases, but Mather thinks that the increased number of nymphal ticks probably resulted in an increase in the number of cases this summer of Lyme disease and babesiosis, a malaria-like parasitic disease.

“Nymphal deer ticks only care about growing into the next stage, which is adult,” Mather said. “The adults show up in October.”

According to Mather, most people are surprised to learn that ticks are dangerous in the fall, as the threat of diseases like West Nile virus ends with the first frost, and people tend to think that the tick threat ends there as well. Deer ticks can’t be lumped into that schedule, however, because the actual season for adult tick activity begins with the onset of fall.

“All of a sudden we’re going to see this explosion of adult ticks,” Mather said. “We see it every year. The concern I have this year is that we were at a record level of nymphal ticks that turn out to be adult ticks in October. If that great number of nymphs that we had in the summer were successful in finding hosts to get their blood meal, they will become a record number of adult ticks.”

Mather said that he personally collected more than 15,000 ticks last year, the most he had ever seen. The mild winter meant that the adults were able to continue their activity until April, resulting in the greater number of nymphs this summer, and the greater number of adults coming in October.

While localities can do things like making people aware of the threat and offering strategies to combat the problem, Mather said that there is also a lot of personal responsibility called for in dealing with the ticks. Most people think they are safe when they spray Deet on their exposed skin, but that is not effective against ticks. Mather recommends spraying clothing with permethrin products as the best protection.

In the summer, when shoes are the first point of contact for the nymphal ticks, footwear should be treated as well. Since the adult ticks tend to move up higher on the foliage, making contact around the knee, it is important to tuck in shirts, and check every day for attached ticks above the belt line.

“We need to have people become more aware of these protection messages,” Mather said.

In addition to deer ticks, there are two other types of ticks present in Rhode Island. They are the American dog tick, which can cause Rocky Mountain spotted fever, and the lone star tick, which can carry human ehrlichiosis. The lone star tick seems to be largely confined to Prudence Island at this point, although small numbers have been found elsewhere. Deer ticks are by far the biggest threat.

Dr. Joseph England is a physician practicing in Jamestown, and a member of the town’s Lyme Disease Reduction Committee, which was started last year. When asked what Jamestown’s response to the increased deer tick threat, England’s response was succinct: “Nothing.”

The problem, according to England, is that the only real way to deal with the problem is to drastically reduce the island’s deer population, and there doesn’t seem to be any interest among the populace in the killing of a great number of deer.

“The committee has met a few times, but we don’t have a plan,” England said. “The goal would be to reduce the deer population. That hasn’t turned out to be a very popular solution over the years, so there is really nothing being done. It’s very hard to get people on board about shooting deer. I’m not sure we see any other viable option at this point, but when that gets presented, it usually doesn’t meet with much interest. I don’t know what we’re going to do.”

It is estimated that there are presently 430 deer on the 9-squaremile island. To reduce tick populations to an acceptable level, that number would have to be thinned to 10 deer per square mile.

“To do that quickly would be impossible,” England said. “It would have to be done over time, and at the same time we have an influx of deer coming from other islands. It has to be an ongoing reduction program even after you reach your target goal. It’s a very difficult problem.”

Professionally, England said his office saw a lot of anaplasmosis this year.

“Lyme disease gets all the press, but there are a number of other tick-borne diseases out there that are just as serious, if not more serious,” England said. “You don’t die from Lyme disease, but you can die from babesiosis and anaplasmosis.”

England said that the occurrence of Lyme disease remained about the same this year, and cases of babesiosis declined. Anaplasmosis cases were up. As Mather reminds us, however, the fall is yet to come, and like Mather, England recommends daily tick checks.

“If you pull a tick off, you most likely prevent any transmission of disease,” England said.

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