Chemist plots ticks' fungal demise

Researchers hope to use fungi to combat deer tick populations

March 25, 1998
Web posted at: 6:49 p.m. EST (2349 GMT)

By Environmental News Network staff

Watch out Lyme disease-carrying black-legged deer ticks -- chemist Patricia Allen wants to make you so sick you die.

Allen, a researcher at Agricultural Research Service, has been exposing black-legged deer ticks to spores of naturally occurring fungi at ARS' Parasite Biology and Epidemiology Laboratory in Beltsville, Maryland, since early 1997. She's tried a half-dozen fungi under controlled laboratory conditions and the most lethal has turned out to be Metarhizium anisopliae, especially to juvenile ticks. Another good candidate is Gliocladium roseum.

The original fungi for the tests came from ticks that died of natural causes in the Beltsville area and nearby Patuxent Wildlife Center. The fungi found on the ticks were tested for their ability to produce a protein-degrading enzyme that is essential for the fungus to be able to penetrate the tick's protective outer case.

The next step was to test the fungi's ability to infect black-legged deer ticks. To do this, healthy, live ticks are dipped into a preparation containing 100,000 to 1 billion fungal spores. Allen also ran some tests where she placed the ticks in small plastic tubes with spore-treated paper wedges at the bottom. Allen maintains the tubes at room temperature and 100 percent humidity and observes the ticks daily for signs of fungal activity.

White-tailed deer, not humans, are the tick's first choice of host

"The ultimate aim of this research," says Allen, "is to develop a practical method of applying pathogenic fungi to the Lyme disease tick."

To that end, Allen will begin a first round of outdoor tests in late April on small-scale plots at Beltsville. She'll spray a commercial preparation of M. anisopliae developed by Ecoscience Corp. of East Brunswick, New Jersey. Of special interest to her is the impact the spraying will have on tick eggs and emerging larvae.

Allen's research is part of a project to explore the potential and safety of using beneficial fungi and nematodes as non-chemical tick controls. Her approach targets black-legged deer ticks because the pests spread the bacterium responsible for Lyme disease in humans. In 1996, the federal Centers for Disease Control and Prevention in Atlanta, Georgia, received more than 16,000 reports of Lyme disease.

Humans aren't the tick's first choice of hosts, according to ARS. The tick's first choice is white-tailed deer, but suburban encroachment on wooded habitat has placed people in closer contact with the deer.

Ticks are also mistakenly referred to by many as insects. But they aren't. Ticks are arachnids -- like mites, scorpions and spiders.

For more information, contact Pat Allen, Parasite Biology and Epidemiology Laboratory, Beltsville, Maryland, (301)504-8772, fax (301) 504-5306, pallen@ggpl.arsusda.gov

Copyright 1998, Environmental News Network, All Rights Reserved

Related ENN Stories:

• Project enlists deer in Lyme disease battle
• Tackling ticks that spread Lyme disease

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