Winter is adult Ixodes pacificus (western black-legged tick) season in California. Laboratory staff have begun surveillance of this tick and the disease-causing bacteria they carry in parks and open space throughout San Mateo County. Ticks are collected by dragging a 1 meter square white flannel flag over the vegetation alongside trails. In November and December, we have collected ticks from Wunderlich County Park near Woodside, Purisima Creek Redwoods Open Space Preserve near Half Moon Bay, Montara Mountain near Pacifica, Skyline Ridge Open Space Preserve, Coal Creek Open Space Preserve and Los Trancos Open Space Preserve near Portola Valley, and Crystal Springs Regional Trail near Millbrae. Tick densities have been lower this season than past years, and several of these parks will require additional flagging to collect sufficient ticks for testing.
Laboratory staff plans to continue tick surveillance into the spring of 2018 to collect nymphal ticks. Although Ixodes pacificus nymphs are more difficult to collect than adults, the infection prevalence of Borrelia burgdorferi, the bacteria that causes Lyme disease, has been found to be higher in nymphs than adults in some California regions.