Don's Home Health Ticks Lyme Disease in California

Lyme Disease in California | UC Integrated Pest Management 2019

First recognized in the United States as an emerging disease in the mid-1970s in Lyme, Connecticut, Lyme disease has been reported in Canada and in many European and Asian countries. The first Lyme disease case in California was reported from Sonoma County in 1978.

Lyme disease is caused by the spirochete Borrelia burgdorferi, a corkscrew-shaped bacterium.

Of the 48 tick species established in California, 6 species attach to humans with some regularity, but only nymphs (an immature tick life-stage) and adult females of the western blacklegged tick (Deer tick), Ixodes pacificus, transmit Borrelia burgdorferi to people.

A rash usually appears two weeks after removal of a tick.

The incidence of Lyme disease in California is usually only 0.2 cases per 100,000 persons per year.

Adult ticks generally seek their hosts from late fall through spring but are most active during winter in the north coast (Mendocino County) and Sierra Nevada foothills (Yuba County). In central and southern California,

The number of confirmed cases reported to state health authorities ranged from 57 to 97 per year between 2005 and 2014. Typical of all disease surveillance systems, the number of Lyme disease cases may be under-reported or misclassified (i.e., disease due to another cause).

The highest average incidence from 2005 to 2014 occurred in the northwestern counties of Trinity (4.5), Humboldt (3.9), and Mendocino (3.9), as well as in the northern Sierra-Nevada counties of Sierra (3.2) and Nevada (2.7). These county estimates vary slightly due to year-to-year variation in reporting, but the patterns of risk remain similar.