Risk of Lyme Disease Transmission is Year-round in Marin & Sonoma Counties

Release date: 
Jan 13

Cotati, CA- Many people enjoy outdoor activities such as hiking, camping, biking, or a picnic in the woods during the winter months. According to the Marin/Sonoma Mosquito & Vector Control District  (MSMVCD) however, winter is also the time of year when adult ticks are abundant.  District officials want to remind outdoor enthusiasts in Marin and Sonoma counties that adult ticks are most active from fall through early spring, while the tiny nymphs are most active in the spring and early summer. Both stages of ticks can transmit the bacterium that causes Lyme disease, as well as other tick-borne diseases.

Piper Kimball, Scientific Programs Director for MSMVCD, stated that most people associate tick season with spring or summer, but ticks are present year-round. Ticks can be found in grassy, brushy, or wooded areas, especially along sides of trails. Contrary to popular belief, ticks do not fly, jump, or fall out of trees. Adult ticks wait on the tips of vegetation with legs outstretched for people or other animal hosts to pass by, while the tiny nymphs that are about the size of a poppy seed are commonly found in leaf litter or on logs and branches. After a tick grasps onto a host, it will crawl in search of a suitable location to attach to the skin.  Generally speaking, the longer the tick stays attached, the higher the risk of disease transmission. The tick may remain attached for many hours or several days, after which it will drop off the host.

The MSMVCD lab conducts tick surveillance and disease testing in various areas within Marin and Sonoma counties. Testing results indicate that an average of 3-5% of ticks collected are infected with the bacterium that causes Lyme disease. While the percentage may appear low, it only takes one bite from an infected tick to transmit a tick-borne disease such as Lyme disease.

"You are the best defense against ticks and tick-borne disease transmission," Kimball said. "Take personal protection measures before, during, and after being in tick habitat, no matter what time of year it is."

Here are some additional suggestions for avoiding tick bites:

  • Wear light-colored clothing with long sleeves and long pants when hiking, walking or working in areas where ticks may be present.
  • Pre-treat clothing and equipment with permethrin to kill ticks.
  • Apply repellent containing DEET (at least 20% concentration) on exposed skin to repel ticks as well as mosquitoes.
  • Showering after being in tick habitat helps detect ticks. Continue to periodically check your body for several days after you have been in tick habitat.
  • Remove ticks promptly using the correct techniques.
  • Contact your physician if you have concerns or become ill after being bitten by a tick.