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[pct-l] Lyme Disease

Ticks' diet of lizard blood linked to West's lower rate of Lyme disease

Scientists have discovered why relatively few people in the American West
develop Lyme disease compared with people who live in the Northeast. According
to a surprise finding reported last week in California Agriculture and in a
recent article in the Journal of Parasitology, the secret lies in lizard
blood.

As infected ticks suck blood from the common Western fence lizard, something
in the lizard's blood kills the bacteria that cause Lyme disease. The bacteria
are destroyed. The ticks and lizards are unharmed.

"Lizards are doing humanity a great service here in the West," said Dr. Robert
Lane, a professor of insect biology in the College of Natural Resources at the
University of California Berkeley and author of recent articles.

"The lizard's blood contains a substance -- probably a kind of heat-sensitive
protein -- that kills the Lyme disease spirochete, a kind of bacterium," he
said.

That the incidence of Lyme disease is higher in New England than in California
had led scientists to believe that something in the environment must be
keeping infection rates low in the West, Lane said in a telephone interview.
Spirochetes that cause the
disease are found in ticks in both regions.

Lane and his colleagues noticed that the Western black-legged tick feeds
primarily on the Western fence lizard, a 2- to 3-inch-long creature that is
found from Washington to Baja California and into Utah and other Western
States.

"They're all over the place," Lane said. "But in the Northeast, black-legged
ticks feed primarily on white-footed mice."

Further study showed that the Western fence lizard, despite being the ticks'
favorite meal, is free of spirochetes but that the white-footed mice are
loaded with them. A typical lizard in the spring can have 30 to 40 juvenile
ticks sucking its blood but it remains healthy, Lane said. About 5 percent of
Western ticks carry Lyme disease spirochetes whereas 50 percent of Eastern
ticks harbor the bacteria.

In the newly reported experiments, the researchers drew lizard blood and added
Lyme disease spirochetes to it. The spirochetes dies within one hour.
Spirochetes placed in mouse blood thrived for days, Lane said. Apparently a
substance in the lizard blood travels to the young tick's mid-gut and kills
all the spirochetes, he said. The adult ticks may then go on to bite humans,
but they will not transmit Lyme disease.

~~~~~
from an article in The San Diego Union-Tribune dated April 19, 1998
By Sandra Blakeslee
NEW YORK TIMES NEWS SERVICE
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