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Deer Device May Lick Ticks

Chemical rub for feeding animals could bring Lyme relief

WEDNESDAY, June 13, 2001 (HealthDayNews) -- Leaders of efforts to claim back the woods from disease-carrying ticks are beginning to sound downright optimistic.

"We've been getting some very promising results in Maryland and New Jersey, and I know that in Westchester [County, north of New York City,] last fall there was a 96 percent reduction in adult ticks on deer," says David Weld, executive director of the American Lyme Disease Foundation.

Much of the credit, it seems, goes to a novel device that treats deer with a tick-killing chemical while they eat.

Ticks bites can transmit the bacteria Borrelia burgdorferi, and the germ causes more than 12,000 cases of Lyme disease a year, says the Centers for Disease Control and Prevention. White-tailed deer are a popular host for the ticks.

Lyme disease often begins with a bull's-eye rash and can progress from flu-like symptoms to more serious and painful swollen joints, neurological problems and sometimes heart abnormalities.

Warnings for people to be wary of the woods have helped check the disease, as has development of a vaccine, say experts. But some say the tick-killing device -- developed by scientists at the government's Agricultural Research Service in Texas and known as the 4-Poster Deer-Feeder -- may hold the most hope.

"To eradicate [ticks] is probably expecting too much, but many people believe that if we got the tick population low enough, the disease cycle would be broken," says entomologist John Carroll, who works on tick-control at the Agricultural Research Service in Beltsville, Md.

"The goal is 90 percent reduction in the number of ticks," Carroll says.

Carroll and his colleagues are more than midway through a five-year test at three sites in different parts of Maryland. At each site, they've placed 25 feeders in an area roughly two miles square.

The tick population in the test areas dropped 50 percent to 60 percent last year, he says. The annual June tick count for this year has just begun, he says.

The feeder consists of a bin filled with corn to attract deer. Each corner of the bin has a paint roller coated with the chemical amitraz. As deer stick their heads into the bin to eat, their necks rub against the roller.

"The feeder is totally passive," Weld says. "The deer apply it to themselves. No spray has to be triggered, none of that stuff. And it won't scare the deer … so they'll come back."

The feeder kills 95 percent of the ticks on a deer, Weld says. "It not only affects their ears, necks and shoulders, but when they preen [or groom themselves], it kills more ticks."

Carroll says removing the deer population by hunting or other means probably would have an effect on the incidence of Lyme disease if enough deer were removed.

"But it's pretty hard to remove all of them, and people don't always want that to happen," he says. "And if you leave even a few, you still can have a lot of ticks on a few deer."

"But with this four-poster technology, ticks are getting killed on the deer. All these deer are sort of working for you, in a way," he says.

Scientists are exploring other means of controlling ticks, including a tick collar that would be zapped onto deer automatically as they approached a particular feeder. Weld says that's "quite expensive" and requires a machine that needs maintenance and also scares away deer.

Others are looking at a bait box containing wads of cotton soaked in a tick-killing chemical that mice would take back to their nest. White-footed mice also carry the disease-causing ticks.

Which chemical, or acaricide, as tick-killing chemicals are called, works best also is being tested.

The Maryland feeders, and others placed in Connecticut, New York, New Jersey and Rhode Island as part of the five-year government experiment, use amitraz, a chemical already approved for use on livestock and given special approval by the Environmental Protection Agency for the feeder study.

Weld says his group is readying a feeder test with a different chemical, permethrin, in Dutchess County, New York, with a $300,000 grant from the CDC.

"It's currently available in some states over the counter, anywhere where there are lots of cattle," he says. "You pour it down the backs of cattle once a month or so."

Permethrin also is used in tick and flea collars for dogs and cats and in hair shampoo for people who have head lice, "so it's something we know a lot about," Weld says.

Before too long, Weld says his Lyme disease foundation expects to have the feeders available for purchase by community groups and others. The U.S. Department of Agriculture has approved marketing the device, and the EPA is considering approval of a chemical for the rollers, he says.

Carroll says homeowners have shown a lot of interest in the feeders.

"It's trying to kill the tick on the host, instead of through a backyard treatment," he says. "A backyard treatment properly done once a year can give you quite good control for that year, but with the four-poster on a larger scale, you can knock the base population [of ticks] in your area down."

"You'll have area-wide control, instead of just individual premises," Carroll says.

What To Do

To find out more about Lyme disease, visit the CDC or the National Institute of Allergy and Infectious Diseases online.

Or, read previous HealthDay articles on Lyme disease.

SOURCES: Interviews with David Weld, executive director, American Lyme Disease Foundation, Somers, N.Y.; John F. Carroll, Ph.D., entomologist, Parasite Biology, Epidemiology and Systematics Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Md.
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