Worms, fungi lead Lyme disease fight Search: A team of three researchers at a Beltsville laboratory is conducting experiments to find a biological assassin for Ixodes scapularis -- the deer tick.

June 09, 1998|By Dennis O'Brien | Dennis O'Brien,SUN STAFF

Dolores Hill thinks she may have found what she has been looking for -- a natural born killer.

Hill, a parasitologist at the Beltsville Agricultural Research Center, has sprayed fields near her lab each week for the past year with thousands of microscopic worms in search of an assassin to knock off Ixodes scapularis, a.k.a. the tick that carries Lyme disease.

She may have found one in Steinernema riobravis No. 355, a microscopic earthworm used since the 1940s to combat the boll weevil and other pests that attack cotton and corn crops.

Hill is part of a team of three researchers at Beltsville's Parasite Biology and Epidemiology Laboratory assigned 18 months ago to a five-year project to find a biological control -- a bug or other organism -- to fight the ubiquitous bug called the deer tick, which has infected 100,000 people with Lyme disease since 1982.

As Maryland enters the peak season for deer tick bites, Hill and colleagues Patricia Allen and John Carroll spray experimental treatments, check tick populations at deer feeders and collect live ticks from the fields near their labs.

The work at Beltsville shows promise in a field of study that has become a major public health issue, according to Howard S. Ginsburg, a research ecologist for the U.S. Geological Service based at the University of Rhode Island in Kingston, R.I.

Ginsburg, who has studied fungus and its potential in fighting ticks, said that he is particularly interested in Allen's work.

"I personally think it's very promising," he said.

Allen is conducting the first ever field tests on a fungus that is used to kill termites and has shown potential for killing ticks under laboratory conditions.

She is trying to come up with an arsenal of fungi equipped with enzymes powerful enough to eat away at the tick's outer protective cuticle and destroy it.

Carroll is testing experimental deer feeding stations that spread a poison on the deer's ears and necks to kill ticks. The feeding stations are designed so that deer must put their heads between two paint rollers covered with Amitraz, a pesticide used to kill mites on honeybees.

Hill, meanwhile, is focused on attacking the tick from the inside.

Hill has been spraying the fields near her lab with the nematodes, a type of microscopic earthworm.

After applying the spray, she waits three to four days and then collects the dead ticks and performs autopsies on them to determine which strains of nematode are most deadly.

After testing the toxic effects of 14 different strains of nematode, Hill finds Steinernema riobravis No. 355 to be the most effective.

Hill says its bacteria-laden gut might make it an ideal tick killer.

"What these nematodes do is actually gruesome to watch," says Hill, holding up a glass jar of the worms, which are so tiny they are barely visible.

No. 355, she said, crawls into the mouths and other openings of the adult ticks. Once inside, itspreads a bacteria that attacks the ticks' internal organs, she said.

"It's not a pretty sight," she said.

First identified in 1975, Lyme disease has been diagnosed in all 48 contiguous states. More than 100,000 cases have been reported to the Centers for Disease Control since 1982, when officials started keeping records.

It causes fevers, rashes and flu-like symptoms and if left untreated, can lead to arthritis, heart disease and damage to the nervous system.

A vaccine to fight Lyme disease was approved by a U.S. Food and Drug Administration advisory panel May 26. It's not clear when it will be available for public use.

But the Beltsville researchers say their work will continue regardless of the vaccine's success.

The vaccine also is widely seen as a short-term solution and experts say wiping out the cause of Lyme disease -- or at least keeping the deer tick in check -- would be more effective.

"The deer tick has caused a lot of devastation up and down the East Coast, particularly in the Northeast," Ginsburg said. "Coming up with a mechanism to bring it under control in the field remains a top priority."

Pub Date: 6/09/98

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