FUNGI AS BIOLOGICAL CONTROL OF LYME DISEASE TICKS
A researcher at The New York Botanical Garden is investigating the potential use of a commonly found species of microscopic fungus as a biological control of the northeastern tick Ixodes scapularis, the key to the spread of both Lyme disease and Human Granulocytic Ehrlichiosis (HGE). Dr. Rosalind Lowen, Honorary Research Associate at the Garden, found that a strain of the fungus Metarhizium anisopliae destroyed 80% of Ixodes scapularis (see http://www.nybg.org/bsci/tick.html) under laboratory conditions. Different strains of this fungus are already used in several countries for pest control, including in the United States where the strain ESF1 is used commercially against cockroaches. If the preliminary results of Dr. Lowen's research are confirmed and the strain's safety for the users and the environment is demonstrated, this microscopic Metarhizium anisopliae could become a weapon against the spread of these two tick-borne diseases. Lyme disease can result in chronic arthritis or permanent neurological damage if untreated. HGE is a recently-described tick-borne disease which, in rare cases, can turn fatal.
Chemical repellents currently used against Ixodes scapularis have limited scope and potential serious side effects. Biological control uses natural predators to control pests, offering a safer and often cheaper alternative to chemical control. Insecticidal fungi like Metarhizium anisopliae kill certain insects by invading the body and multiplying throughout. The insect dies from tissue destruction caused by the proliferation of the fungus and the production of fungal toxins. The fungus then emerges from the body in the form of spore- producing filaments. Scattered by the wind and the rain, the spores spread the infection to other ticks. Because of the danger of the fungal toxins contaminating the environment, this strain of Metarhizium anisopliae will have to pass extensive safety tests before any possible commercial application. Unable to grow at or above 95 degrees F., Metarhizium anisopliae is not a threat to humans and other mammals.
Lyme disease is a tick-borne infection caused by the spirochete Borrelia burgdorferi, a coiled bacterium found in the blood of contaminated white-footed mice and transmitted to ticks when they feed on mouse blood. The infected tick spreads the bacterium to its subsequent hosts: animals such as deer, small mammals, and humans. Currently, there is no vaccine against this infection and no early reliable medical test to detect the onset of the disease. HGE was first described in 1994. Its causative agent is not identified yet and its diagnosis is difficult. Easily treated with antibiotics for the most part, it is nevertheless fatal in 5% of the reported cases. In Westchester County, one of Lyme disease's hot spots in the eastern U.S., 79% of the adult ticks are estimated to be carrying either infection. The population of Ixodes scapularis is spreading. The National Center for Infectious Diseases recently reported Lyme disease ticks in a New York City park, proving that Ixodes scapularis is not limited to countryside settings.
Dr. Lowen is conducting this research in collaboration with Drs. Richard Falco and Thomas Daniels from Fordham University's Calder Center in Armonk, New York.
Principal Investigator: Dr. Rosalind Lowen, Honorary Research Associate Public Relations: Annick Sullivan, 718-817-8815
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