Posted January 26, 2015
Last modified March 10, 2015
Ticks. Even now, with snow, ice and frigid temperatures holding them in abeyance, the very mention of the little critters can make your skin crawl.
But it gets worse, because those critters carry diseases like Lyme, anaplasmosis and babesiosis, illnesses that are debilitating as they are, at times, baffling to physicians.
Chuck Lubelczyk, a field biologist with Maine Medical Center Research Institute, didn't have much good news about the havoc ticks can and are wreaking in Maine when he spoke at a November meeting of the Maine Island Coalition.
In 2013, Lubelczyk said, some 1,300 cases of Lyme disease were reported in Maine.
"That is thought to be just a fraction of the actual number of cases," he said.
Most of the cases were tied to Mount Desert Island and coastal Cumberland (353 cases) and York (215 cases) counties. Based on rates per 100,000 people, Knox, Lincoln and Waldo counties topped the list for Lyme reports.
Coastal areas from Brunswick to MDI are "the hottest areas for deer ticks," Lubelczyk said.
In answer to a coalition member's question, he said a Lyme vaccine has been developed that is 70 percent effective, but it must be renewed each year, and pharmaceutical companies have not found it commercially viable. The vaccine also has some negative side effects, he said.
About 15 species of ticks have been found in northern New England. Most are found along the coast from Kittery north to MDI, though one map Lubelczyk showed using 2009 data suggested they have begun ranging some 50 miles inland.
Information about disease transmission varies widely, Lubelczyk acknowledged, but according to the research, ticks must feed on a host for at least 36 hours to transmit the Lyme bacterium.
Deer ticks, the most common carrier of Lyme, are most active in the spring and fall.
"These are two times of the year that should be of more concern," Lubelczyk said.
A graph showed that the nymph—the stage at which the tick is almost as small as the period at the end of this sentence—is most active in June and July. Adult tick activity peaks in May, drops off sharply in the summer, then spikes in October and November. Adults are about the size of an apple seed.
After a late-August hatch, the deer tick nymphs feed on mice, chipmunks and raccoons, he said.
Dog ticks, which have either a white "scutum"—a shield-like shape on their backs—or white "racing stripes," also on their backs, do not transmit Lyme.
Adult dog ticks are large in the summer while deer ticks are small, Lubelczyk reported. Those found on people and animals in fall or spring are likely to be deer ticks.
Deer ticks also are the culprits for anaplasmosis and babesiosis, both of which are rare in Maine.
"They're about ten years behind Lyme," he said, "but they're following a similar track, geographically."
Two types of Powassan, also known as deer tick virus, are transmitted by the deer tick. Maine recorded four human cases between 1999 and 2004, and one human case—which proved to be fatal—in 2013. Skunks and raccoons were found to have the virus near where the human cases were recorded.
Just 2 percent to 4 percent of ticks have been found to carry Powassan.
TICK HABITAT, DEER HOSTS
Ticks find deciduous forest and shrubs, often those at the line between woods and lawn, most desirable, Lubelczyk said. Open areas and spruce and other softwood stands are not favorable, because "ticks dry out" in such places.
Any discussion of ticks and disease leads to deer.
"White-tailed deer are the definitive host," he said, "the most obvious and preferred host." About 100 ticks can be found on one deer, with each tick laying up to 3,000 eggs.
York County currently has 80-90 deer per square mile, making it easy for the ticks and the disease to spread. Reducing deer populations to below 40 per square mile results in a drop in tick populations, Lubelczyk said.
In answer to a question about the role of mice in spreading Lyme, he said while they are "a reservoir" for the disease, so are birds, chipmunks, squirrels and other small animals. Focusing on deer population management is the best course, he said, but "Communities, especially island communities, shouldn't exclude any one tool."
Monhegan eliminated all deer and the tick population dropped, but didn't disappear. In fact, the ticks adapted to the island's Norway rats, he said.
Along with pesticides, which can be applied in the areas where woods and yards meet, Lubelczyk said there are "green" alternatives, such as spraying rosemary and winter green oil, which can drown the ticks.
Using guinea hens to keep a yard clear of ticks—a strategy some people attest to—doesn't work, he said. Hens used in high tick areas were dissected and no sign of the bugs were found in their gullets, but the birds were found to be hosts for the ticks.
One response to being exposed to ticks that does work, he added, is to throw clothes worn in tick habitat directly into a dryer on high heat for 30-60 minutes.