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Getting the Dirt on Parkinson's

Soil bacteria may be linked to motor-neuron disease, says study

WEDNESDAY, Sept. 12, 2001 (HealthDayNews) -- A bacteria commonly found in soil may trigger Parkinson's disease, says a new study.

The bacteria Nocardia asteroides causes permanent changes in brain chemistry and produces tremors and muscle rigidity in some laboratory animals, the researchers report.

"This could potentially be very significant," says lead study researcher Blaine Beaman, professor of medical microbiology at University of California at Davis. "If Nocardia is involved in the development of Parkinson's disease -- and I think it is -- understanding the mechanism might permit the development of prevention and therapy."

The study will be presented tomorrow at the biannual meeting of the Society for General Microbiology at the University of East Anglia in England.

Nocardia asteroides is known to cause infections of the lungs and skin in humans and animals, entering the body mainly through inhalation of dust, Beaman says.

Though the prevalence of illnesses caused by Nocardia has not been determined, one large study found half the population has antibodies to it, indicating exposure to the bacteria is common, Beaman says.

Because illnesses caused by Nocardia can be mistaken for other lung infections, Nocardia is not often fingered as the culprit, Beaman says.

Beaman and his colleagues injected mice and monkeys with the Nocardia bacterium. About 10 percent to 20 percent of the animals developed Parkinson's-like symptoms, the study found.

Autopsies on the animals showed the bacteria had traveled to the brain and caused irreversible damage.

Using tissue cultures, researchers determined the bacteria killed nerve cells in the substantia nigra, the portion of the brain responsible for producing dopamine, a brain chemical that controls motor skills and movement. A lack of dopmine causes the tremors and stiffness typical of Parkinson's.

Parkinson's, a degenerative diseases, afflicts 1 million Americans.

The exact cause of Parkinson's disease is not known, but recent research has implicated pesticides, herbicides and genetic factors.

Dr. Robert G. Feldman, professor of neurology, pharmacology and environmental health at Boston University, is very skeptical that a bacterium is the cause of Parkinson's. If bacteria commonly found in the soil were to blame, many more people would have Parkinson's, he says.

Also, he says many environmental substances, including lead, manganese, iron and some pesticides, can cause changes in brain chemistry. The key to unlocking the mystery of Parkinson's is to determine the genetic factors that interfere with the mechanisms that protect the brain against such environmental assaults, he says.

"The bottom line is: I wouldn't get too excited about it [the study]. There is increasing evidence that genes determine an individual's likelihood of developing Parkinson's and other related conditions," Feldman says.

Beaman says the research does not discount the possibility that genetic factors make some people more susceptible to the bacterium than others. For every 100 mice injected with the bacteria, only 10 to 20 developed a disorder, indicating that individual differences play a role, he says.

"Many factors are probably involved in causing Parkinson's disease," Beaman says. "Studies show that people who develop the disease have come into contact with something in their environment, which, combined with the normal aging process, helps to trigger the illness."

Beaman does not recommend that people stop gardening. "I garden and I don't worry about the risk. There is some risk in just about everything you do, whether it's driving or crossing the street. Besides, Nocardia is also found in house dust," Beaman says.

What To Do

For more information on the brain disorder, check the Parkinson's Disease Foundation, the National Institute of Neurological Disorders and Stroke or the Michael J. Fox Foundation for Parkinson's Research.

SOURCES: Interviews with Blaine Beaman, Ph.D., professor of medical microbiology, University of California at Davis; Robert G. Feldman, M.D., professor of neurology, pharmacology and environmental health, Boston University, Boston, Mass.; study presented at the biannual meeting of the Society for General Microbiology at the University of East Anglia, England
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