In Sonoma County parks and other places where people enjoy getting close to nature, a tiny part of nature is ready to bite.
It’s tick season, which runs year-round in the region’s woods and fields, but peaks in the spring, or whenever spring-like weather arrives. And last month’s warm spell, prompting flowers and trees to blossom and grapevines to bud, kicked it off, officials said.
“It’s early spring,” said Karen Holbrook, deputy health officer, with spring officially two weeks away.
“I really do want people to be aware of the risk and to take precautions,” she said, noting that ticks carrying Lyme disease live in the area. The best approach, if bitten, is to immediately and safely remove the tick, save it for identification and to consult a health care provider, Holbrook said.
But the greatest risk is from ticks so small their bite may go unnoticed.
Western black-legged ticks in their immature stage, known as nymphs, measure one-twentieth of an inch, about the size of a poppy seed. They can bite a person, transmit the bacteria that causes Lyme disease and drop off without the human knowing anything happened.
Sometimes, a distinctive bulls-eye rash is the first evidence of an infected tick bite, or it’s the onset of the flu-like symptoms of Lyme disease: chills and fever, headache, fatigue and muscle pain.
Patients treated with appropriate antibiotics in the early stages of Lyme disease usually recover rapidly and completely, according to the Centers for Disease Control and Prevention. Long-term symptoms of Lyme disease include arthritis, pain, heart irregularities and brain and spinal cord inflammation.
Sonoma County is ground zero for Lyme disease in California, with 41 confirmed cases — more than any other county — from 2010 to 2014.
Mendocino and Humboldt counties have fewer cases, but join Sonoma on the list of nine counties with the highest rate of cases per 100,000 people.
Put in perspective, California’s overall Lyme disease infection rate of 0.2 cases per 100,000 is minuscule compared with rates of 50 to 70 cases in New England. There were 410 Lyme disease cases in California between 2010 and 2014, less than one-half percent of the 121,501 reported cases nationwide, according to the CDC.
Since many cases go unreported, the CDC cites studies estimating that about 300,000 people contract Lyme disease each year.
Sonoma County’s average of eight cases a year is “a definite concern,” but a lesser threat than conditions such as cancer, diabetes and cardiovascular disease, Holbrook said.
At Annadel State Park, the Santa Rosa recreational mecca that attracts about 150,000 hikers, runners, mountain bikers and horseback riders a year, people and black-legged ticks, commonly called deer ticks, are on a collision course.
“Those little guys wreak havoc,” Annadel Park Ranger Bob Birkland said. Bitten by ticks more times than he can remember in a 39-year career in state and county parks, Birkland said he’s more concerned about the small arachnids than rattlesnakes.
“There are a lot more ticks,” he said.
He cringes at the sight of park visitors, under the false impression that ticks only come out in the summer, lying down in the fresh spring grass. It’s a terribly bad idea, Birkland said. At the very least, people should lie on a blanket and shake it when they get up
Birkland said he sprays repellent containing DEET on his trouser legs, as well as on the legs and underbelly of his horse, when he goes off-trail. Staying on trails is the primary advice experts give to avoid tick bites.
Sitting down on leaf litter or fallen logs in oak-madrone woodlands is sheer folly because that’s where ticks in the nymph stage of growth live and are the most active in spring and early summer. Adult ticks seek blood-bearing hosts more actively, climbing to the tips of grasses and shrubs in hopes of making contact.
Birkland said he’s seen 20 or more ticks on a blade of grass “waiting to grab you.”
Nymphs at Annadel have the highest rate of Lyme bacteria infection, at 7.3 percent, among the seven state and regional parks surveyed by the Marin/Sonoma Mosquito & Vector Control District. The rate among adult ticks at Annadel is 2.6 percent.
At Sugarloaf Ridge State Park, 5.3 percent of nymphs and 0.8 percent of adults are infected, according to testing by the district from 2008-2014. At Spring Lake Regional Park in Santa Rosa, 3.6 percent of nymphs and 1.1 percent of adults carry the bacteria.
At Jack London State Historic Park near Glen Ellen, 4.5 percent of adults and 0.9 percent of nymphs are infected. Lower rates of infection were found in ticks at Foothill, Shiloh Ranch and Sonoma Valley regional parks.
“The ticks are definitely active,” said Angie Nakano, scientific programs manager for the district, which began tick surveillance in February.
At the Sonoma County Public Health Laboratory on Chanate Road, technicians tested 32 ticks brought in by people for analysis the week of Feb. 22 and found one infected. The week before, none of the 46 ticks tested were positive for the Lyme disease bacteria.
“It’s prime time,” lab director Mike Ferris said, noting that the lab — which charges a $31 fee — is now testing as many as 50 to 100 ticks a week.
Technicians slice off the tick’s head and crush the body with a scalpel to squeeze the midgut onto a microscope slide. A goat antibody, which attaches to the surface of Lyme disease bacteria, is applied, followed by a rabbit antibody that piggybacks onto the goat antibody and carries a “fluorescent trigger.”
Under ultraviolet light in a small, darkened corner of the lab, the corkscrew-shaped Lyme disease pathogen, magnified 500 times, shows up bright green against a drab olive-colored background.
“See those squiggly lines? That is Lyme disease,” Ferris said.
The Bay Area Lyme Foundation announced last month that it is offering free tick testing to U.S. residents, conducted by a lab at Northern Arizona University. For information, go to bayarealyme.org/lyme-disease-prevention/tick-testing.
The western black-legged tick is one of four California species that commonly bite people, and the only one known to transmit Lyme disease. A positive tick test does not confirm infection in a person, nor does a negative result rule it out.
Ticks transmit at least six other diseases to people in California, none as prevalent as Lyme disease.