URI entomologist: Gauge risk of Lyme disease by rain gauge
Deer ticks continue to spread into northern Rhode Island
 KINGSTON, R.I. -- April 28, 2003 -- The invasion of northern Rhode Island by Lyme disease-carrying deer ticks is expected to continue this summer following last year’s 56 percent increase in nymphal tick populations. So says Thomas Mather, a professor of entomology at the University of Rhode Island who has been monitoring the state’s tick population for more than a decade.
 But the degree of risk for contracting Lyme disease will depend in large part on the amount of precipitation the region receives in June and July.
"Tick activity levels appear to depend almost entirely on the amount of soil moisture in late June and early July," explained Mather. "If we have a drought beginning in late June, then ticks will become inactive by early July and the risk for contracting Lyme disease will be greatly reduced. But if it’s wet in June and July then residents will need to take precautions against the disease into August."
The Centers for Disease Control and Prevention have established a national goal of reducing the rate of Lyme disease to 9.7 cases per 100,000 people by the year 2010. In Rhode Island the current rate is between 30 and 60 cases per 100,000 people.
"Since deer ticks made such a dramatic move into the northern part of the state last year, northern Rhode Islanders need to be much more alert and concerned about Lyme disease than they have been in the past," Mather said. "The ticks will likely have a greater impact in that area this year, so the medical community must be alert for tick-borne diseases. I expect Lyme disease cases will increase considerably there."
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Mather recommends that all Rhode Islanders take precautions to prevent contracting Lyme disease and institute tick control strategies around the yard. He recommends:
- Check thoroughly every day for ticks
- Apply a repellent containing Permethrin on clothing whenever going outdoors
- Keeping the edge of the yard clear of leaf litter because that’s where ticks are most prevalent; and
- Consider hiring a professional to apply a tick treatment throughout the yard.
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Mather said that despite this year’s severe winter weather, adult deer ticks have been active throughout Rhode Island since early March. "That’s typical, but it tends to surprise people every year," he said. "The March weather warms up enough for adult ticks to become active, but adult ticks are less of a concern than the nymphs that become active at the end of May. Adults are larger so they’re much more easily seen and are usually removed before they can transmit the Lyme disease pathogen."
Adult ticks must be attached for 48 hours to transmit the disease pathogen, while nymphs, which are tiny and difficult to see, need only be attached for 24 hours to transmit the infection.
In addition to Lyme disease, deer ticks also carry a malaria-like protozoan that causes babesiosis and a bacterium that causes human granulocytic ehrlichiosis (HGE). Like Lyme disease, these infections cause flu-like symptoms and are difficult to diagnose, but unlike Lyme disease, they can be fatal.
"Babesiosis is only found in areas where ticks are hyper-abundant, and for now, at least in Rhode Island, that still means it is limited to South County," Mather said. "And the rate of HGE infection in ticks is still quite low, making it somewhat less of a concern."
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