The western fence lizard doesn't peddle insurance like its relative, the gecko, but it provides a potentially more valuable service to North Coast residents by shielding them from Lyme disease in an unusual way, scientists say.
Researchers working primarily in the Ukiah and Hopland areas of Mendocino County discovered the role of the common lizard, also known as a blue-belly, in cleaning Lyme disease bacteria out of ticks that transmit it to humans.
“It's an incredibly simple system,” said Robert Lane, a UC Berkeley professor emeritus of medical entomology whose investigation of Lyme disease transmission in nature began three decades ago.
Simply put, the lizard's blood contains a protein that kills the Lyme disease bacteria in the gut of an immature western black-legged tick, which then molts into a disease-free adult tick.
Under a lab microscope, Lane watched the spiral-shaped bacteria, known as spirochetes, die within an hour of being immersed in lizard blood.
“You could see it with your own eye,” he said.
Sonoma County is a ground zero for Lyme disease in California, with 73 confirmed cases — more than any other county — in the past decade.
Mendocino and Humboldt counties have fewer cases, but rank second and third statewide in the rate of cases per 100,000 people.
California's overall Lyme disease infection rate of 0.2 cases per 100,000 pales compared with rates of 50 to 70 cases in New England, but without the lizard's presence it would likely be higher, Lane said.
The little lizard, which kids and cats are fond of catching, “serves a protective function,” he said. “It's reducing the likelihood that you or I would be bitten by an infected adult tick.”
It's range is the far west, and primarily California.
Lane said his discovery, published in 1998, stemmed from a “conundrum.”
A study of about 150 people in a small, rural community near Ukiah in the late 1980s found that 24 percent tested positive for Lyme disease, a level comparable to “hyper-endemic” areas of the northeast United States.