Ticks are present throughout California and can transmit various pathogens. Understanding common species, their habitats, and associated diseases is important for protecting oneself during outdoor activities.
Common Tick Species in California
Several tick species are found across California’s varied landscapes. The Western Blacklegged Tick (Ixodes pacificus) is a primary vector for Lyme disease in the western United States. These ticks are found in wooded and brushy areas, feeding on large mammals and humans. Adults are most active from fall through early spring.
The Pacific Coast Tick (Dermacentor occidentalis) inhabits coastal regions, sagebrush, and desert areas. The American Dog Tick (Dermacentor variabilis) is present at lower elevations, favoring grassy habitats. The Rocky Mountain Wood Tick (Dermacentor andersoni) is found in shrubby and wooded mountainous regions.
Where Ticks Live and Thrive
Ticks thrive in areas with dense vegetation, including tall grasses, brush, wooded environments, leaf litter, rocks, and fallen logs. They do not fly or jump; instead, they wait on vegetation for a host to brush against them. Ticks are widespread across California’s diverse geography, from coastal regions to the Sierra Nevada foothills and parts of the Central Valley.
Tick activity varies by species and season, though they can be encountered year-round. Many species are most active during spring and early summer. Western Blacklegged Ticks, a significant vector for Lyme disease, remain active through fall and winter, with nymphs peaking in late spring/early summer and adults in late fall/winter.
Diseases Carried by California Ticks
Ticks in California can transmit several bacterial diseases. Lyme disease, caused by Borrelia burgdorferi, is primarily transmitted by the Western Blacklegged Tick (Ixodes pacificus). Symptoms often include an expanding red rash (sometimes bullseye-shaped) appearing 3 to 30 days after a bite, accompanied by fever, chills, headache, and muscle or joint pain. Untreated Lyme disease can affect joints, the nervous system, or the heart. Transmission typically requires an infected tick to be attached for at least 24 to 36 hours.
The Western Blacklegged Tick also transmits Anaplasmosis, causing flu-like symptoms. Rocky Mountain Spotted Fever (RMSF) is transmitted by the American Dog Tick, Pacific Coast Tick, and Rocky Mountain Wood Tick; its symptoms include fever, headache, muscle pain, and sometimes a rash. Transmission can occur relatively soon after attachment. Tularemia can be carried by the Pacific Coast Tick, American Dog Tick, and Rocky Mountain Wood Tick.
Borrelia miyamotoi Disease (BMD), transmitted by the Western Blacklegged Tick, has been identified in California. BMD symptoms are similar to Lyme disease but may include relapsing fevers and typically lack the bullseye rash. Human granulocytic ehrlichiosis (HGE) cases have been reported in Northern California, with Ixodes pacificus capable of transmitting the agent. HGE symptoms often resemble influenza, including fever, headache, and muscle aches.
Preventing Tick Bites
Reducing the risk of tick bites outdoors in California involves several measures. Wear long pants, long-sleeved shirts, and closed-toe shoes. Tuck pant legs into socks or boots to minimize exposed skin. Light-colored clothing makes ticks easier to spot.
Use EPA-registered repellents on exposed skin and clothing, following product instructions. Effective ingredients include:
DEET (at least 20%)
Picaridin
IR3535
Oil of lemon eucalyptus (OLE)
Para-menthane-diol (PMD)
Treat clothing and gear with 0.5% permethrin, which kills ticks on contact, but do not apply permethrin directly to skin. When hiking, stay in the center of marked trails and avoid tall grass, dense brush, and leaf litter.
After returning indoors, conduct thorough tick checks on yourself, children, and pets. Focus on areas like the scalp, hairline, behind the ears, armpits, groin, belly button, and behind the knees. Other preventative steps include:
Placing outdoor clothes in a dryer on high heat for at least 10 minutes to kill any remaining ticks.
Showering within two hours of coming inside to wash off unattached ticks.
For properties bordering natural areas, maintaining a clear yard by removing leaf litter, trimming grass, and creating gravel or wood chip barriers to reduce tick habitats.
What to Do After a Tick Bite
If a tick is found attached, prompt removal is important. Use fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible. Pull upward with steady, even pressure, avoiding twisting or jerking, which can leave mouthparts in the skin. Do not crush, burn, or smother the tick with petroleum jelly or nail polish, as these methods can irritate the tick and increase disease transmission.
After removal, clean the bite area with soap and water or rubbing alcohol, then apply an antiseptic. Monitor the bite site for several weeks for any rash, especially an expanding red or bullseye-shaped one. Watch for symptoms like fever, chills, headache, muscle or joint aches, fatigue, or swollen lymph nodes. If a rash or these symptoms appear, or if the tick cannot be fully removed, seek medical attention. Removing the tick quickly reduces disease transmission likelihood.