Hikers, bikers, and other outdoor enthusiasts in northern California might need to take extra precaution against the double threat of two tick-induced bacteria, a new study suggests.

Researchers at Stanford University’s Stanford Woods Institute for the Environment found the bacterium responsible for causing Lyme disease—Borrelia burgdorferi, and the newly recognized human pathogen Borrelia miyamotoi—in ticks sampled throughout most of the Bay Area parks examined in the study.

The study, which will be published in the U.S. Centers for Disease Control and Prevention's (CDC) journal Emerging Infectious Diseases, brings up concern over Californians’ exposure to both B. miyamotoi and Lyme disease.

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What Did Researchers Find?

Lyme disease is an infectious tick-borne disease caused by the bacterium B. burgdorferi. In California, where the study took place, Western black-legged ticks are responsible for transmitting the disease to humans.

In the 12 Bay Area recreational areas tested, researchers found slightly higher rates of ticks infected with B. miyamotoi than those infected with B. burgdorferi. Also surprising was the relatively low rate of B. burgdorferi found in adult ticks. However, ticks infected with B. burgdorferi were also found in in chaparral habitats far from wooded areas, indicating the spread of the bacterium.  

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What Does Lyme Disease Look Like?

Symptoms of Lyme disease can be fairly vague, and include fever, headache, and fatigue, but the rash that often ensues is a more conspicuous giveaway.

Therefore, Lyme disease can be difficult to pinpoint for a couple reasons: either because the symptoms are so indefinite, or, as Dr. Anne R. Bass, program director of the Rheumatology Fellowship Program at the Hospital for Special Surgery in New York City explained, because Lyme disease is often over-diagnosed.

But Bass, who was not part of the study, said, “if you understand what the manifestations of the disease are, it follows pretty standard patterns at certain stages.”

How Does Lyme Disease Spread?

While the researchers indicate in the study that the spread of Lyme disease possibly be due to climate change or the movement of infected animals, Bass notes that not all areas are conducive to the spread of the disease.

“Lyme isn’t everywhere,” Bass said. “It’s really only in the ecosystems that can support the bacteria.”

Ticks have a complicated life cycle, Bass said, but it is one that depends on being in the presence of animals that ticks can feed on, generally in wooded areas that support such wildlife. The bacteria can't survive in urban areas, but borders between lawns and wooded areas are optimal for ticks.  

What Can You Do?

A few simple precautions can go a long way toward preventing tick bites and Lyme disease. Dr. Bass recommends taking the following actions:

  • Covering up with long pants and sleeves
  • Keeping lawns cleared from large piles of wood where mice can hide
  • Using bug repellents effective against ticks
  • Taking a hot shower at the end of the day to remove any lingering ticks
  • Performing a full body check at the end of the day

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