Researcher Dan Salkeld holds a wood rat at the Thornewood Open Space Preserve in San Mateo County. Salkeld and his team were doing research on bacteria that causes an illness similar to Lyme disease. (Courtesy Nathan Nieto)

Lyme-like disease bacteria found in Peninsula

Lyme disease has historically been rare in California but an apparent close cousin of the bacteria, which causes a similar tick-borne illness, has been found on the Peninsula.

San Mateo and Santa Clara County parks that were surveyed and found to contain infected ticks include the Monte Bello and Thornewood Open Space Preserves in the Santa Cruz Mountains, the Windy Hill Open Space Preserve in Portola Valley, Foothills Park in Palo Alto, and Hidden Villa in Los Altos Hills.

No human in California has been diagnosed with the Lyme-like infection, but the researchers who confirmed the pathogen’s presence have urged residents to take precautions against ticks, and to seek medical help if they experience Lyme symptoms after visiting a park or wilderness area.

Early symptoms can include fever, relapsing fever, chills and headache, according to Colorado State University Disease Ecologist Dan Salkeld, but he could not say whether the “bull’s eye” or target-shaped rashes often associated with Lyme-bearing tick bites are likely to occur with this new, similar infection.

Salkeld and his fellow researchers found infected ticks while conducting a study at Stanford University’s Stanford Woods Institute for the Environment, and he said the findings have since been confirmed with repeated testing, both by his team and by the California Department of Public Health.

The bacterium identified in the studies was Borrelia miyamotoi, which Salkeld said has been a known human pathogen for about three years. And while the first human case has yet to be diagnosed in California, there have been human diagnoses in the northeast United States and in Asia, Salkeld noted.

Prompt detection and treatment are crucial. According to the Centers for Disease Control website, untreated Lyme disease can lead to pain, arthritis, facial palsy, heart problems, and inflammation of the brain and spinal cord.

“If you’re hiking frequently, think you might have been in tick habitats, and have symptoms, that’s something to raise with your physician,” Salkeld said.

However, Salkeld did not discourage Bay Area residents from enjoying the outdoors. “None of this need be alarming,” Salkeld claimed.

The researcher said hikers should wear long pants, use tick repellant, and avoid walking close to vegetation. He also recommended checking yourself for the presence of ticks after visiting open space areas.

Those ticks might be hard to spot, however, as they feed on humans during the nymph stage of their life cycle, when they are smaller than poppy seeds, Salkeld noted.

Scientists credit the western fence lizard for preventing Lyme from making inroads in California. A protein in the reptile species’ blood kills Borrelia burgdorferi, the bacteria that causes Lyme disease. And because nymphal ticks commonly feed on fence lizards, few adult ticks in the state carry the Lyme pathogen.

Could the western fence lizard similarly slow or prevent the spread of Borrelia miyamotoi?

The new bacterium is in the same family as Borrelia burgdorferi, Salkeld said, and the two kinds of spiral-shaped bacteria are so similar that they look alike under a microscope, and can only be distinguished with DNA testing.

But despite that similarity, Salkeld said it is not yet known whether the fence lizard’s Lyme-killing blood protein will have any effect on the new Lyme-like microbes.

Another unknown is whether the bacterium represents a hazard to pets, Salkeld said, noting that dogs can be infected with Lyme disease.Lyme diseasePeninsulaSan Mateo CountySanta Clara Countytick-borne illness

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