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Lyme disease tied to year-round tick season round in Bay Area: Experts advise protective clothing, doing tick checks after outdoor outings
August 25, 2014, 05:00 AM By Angela Swartz Daily Journal

It’s best to load up on DEET and check for ticks year-round to prevent Lyme disease, not just during what was once thought to be the typical West Coast tick season in fall, according to a new study.

New research shows ticks that carry Lyme disease in Northwest California are active throughout the year, making the threat of Lyme disease year-round, according to researchers at the California Department of Public Health Vector-borne Disease Section and University of California at Berkeley.

“The most important thing is that Lyme disease is in the Bay Area and we now know it unfortunately it’s year-round,” said Linda Giampa, executive director of the Bay Area Lyme Foundation. “We want people to enjoy, but be aware and do Lyme checks.”

In San Mateo County, the Mosquito and Vector Control District collects western black-legged ticks every year from its parks, said Vector Ecologist Theresa Shelton.

They are tested for borrelia burgdorferi, the bacteria that can causes Lyme disease and Borrelia miyamotoi, a bacteria that can cause tick-borne relapsing fever, to determine the infection rates at each park.

But while the district keeps its eye on ticks, it does not proactively try to prevent them itself.

“We do not normally do any tick control,” Shelton wrote in an email. “We focus on public education for residents to increase awareness of tick-borne diseases and help them prevent tick bites. ... The district would consider tick control along trails if the infection rates were exceptionally high.

Shelton said the district did some tick control several years ago around a campsite where they were present around the tent cabins but such efforts are not typical.

“In general, we don’t have a chemical tick control program though because it only temporarily reduces tick populations and we want to avoid widespread pesticide applications in natural areas,” Shelton wrote.

Gampa said the new information on ticks isn’t reason to panic.

“We don’t want to be alarmist,” Giampa said. “Everybody enjoys the outdoors and goes hiking and biking and there’s very, very simple things to do.”

Tips for preventing Lyme disease include wearing socks, white, tucking hair away in a hat, wearing long-sleeved shirts, wearing light-colored clothing and hiking boots. The most important thing to do is tick checks when one gets back from outdoor activities. It’s also recommended to walk in the middle of trails and avoid sitting on logs or leaning on trees. Putting clothes in a hot dryer for one hour after being in woods is also advised. Also, using DEET for skin and permethrin for your clothes can protect one for six weeks. The group recommends checking pets’ heads, legs and stomachs and for ticks, Giampa said. If a tick is found, it’s best to remove them as soon as possible with tweezers. 

Scott Morrow, San Mateo County public health officer, said the county does get a handful of Lyme disease cases reported.

“We don’t have a very good understanding of the infection rate in the ticks,” he said. “The adults tend to run in the 1 to 2 percent ranges, while infantile ticks can have really high infection rates.”

Morrow is part of a state Lyme disease advisory task force.

“There’s been a lot of public education that ‘yes, you can get Lyme disease in California.’”

In San Mateo County, ticks carrying Lyme disease were confirmed in Jasper Ridge Biologic Preserve, Pulgas Ridge Open Space Preserve, Thornewood Open Space Preserve, Windy Hill Open Space Preserve and Wunderlich County Park.

The new findings suggest that the timing of peak tick activity of western black-legged ticks — the ticks most commonly known to carry Lyme disease in Northwest California — is largely predictable and year-round. In general, tick larvae are active April to June, and sometimes activity extends into October, while adult ticks are active from October to May. From January to October, nymphal ticks — younger and smaller than adult ticks but older than larvae — become active.

A recent study published in a journal of the Centers for Disease Control that found that ticks carrying the bacteria that cause Lyme disease are widespread in the San Francisco Bay Area.

“Based on these results, tick season in Northwestern California is longer than even we expected and quite different from patterns in the Northeast USA,” said study author Daniel Salkeld, a research scientist at Colorado State University, said in a prepared statement.

Salkeld is now supported by the Bay Area Lyme Foundation to continue research into the ecology of ticks and their pathogens in California.

Symptoms of the first stage of Lyme disease include headaches, flu-like symptoms, joint pain, fatigue and sometimes a rash that has many different shapes including one that may look like a bull’s-eye centered on the tick bite. The highest reported incidence of Lyme disease in humans in Northwest California correlate to the times when the younger, smaller ticks which are smaller than a poppy seed, are most active.

Compounding the growing problem of Lyme disease in northwestern California is that the host animals that most commonly carry Lyme disease are also active throughout the year and often live for extended periods of time, compared to host animals in the Northeast United States. In the Northeast, few white-footed mice, the host animals that most commonly carry the bacteria that causes Lyme disease in that region of the country, live through the cold winters. By contrast, the host animals that most commonly carry the bacteria that causes Lyme disease in California, western gray squirrel and dusky-footed wood rat often live longer than one year and can carry the bacteria throughout the year.

Full lists of prevention tips and symptoms can be found at

The study “Seasonal activity patterns of the western black-legged tick, Ixodes pacificus, in relation to onset of human Lyme disease in northwestern California” is available at

(650) 344-5200 ext. 105



Tags: disease, ticks, california, bacteria, active, carry,

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