Tick-Borne Disease

Tick surveillance is focused primarily on city parks, open spaces, and trails within the East Bay Regional Park system. The western blacklegged tick (Ixodes pacificus) is the main vector of Lyme disease in Alameda County. Lyme disease is caused by the bacterium Borrelia burgdorferi. I. pacificus is also the main vector of tick-borne relapsing fever which is caused by the bacterium Borrelia miyamotoi. The western blacklegged tick has four life stages: egg, larva, nymph, and adult. Both nymphal and adult ticks can bite humans and have the ability to transmit the bacteria. All life stages can be found in Alameda County, but tick abundance varies across the County.

In addition, I. pacificus ticks can transmit Anaplasma phagocytophilum, a bacterium which causes Human Granulocytic Anaplasmosis. In 2022, the District started to test I. pacificus ticks for A. phagocytophilum. In 2019, the District started testing for the presence of tick-borne diseases in Pacific Coast ticks (Dermacentor occidentalis) and Western American dog ticks (Dermacentor similis). The Pacific Coast tick is the primary vector of Rickettsia philipii, the causative agent of Pacific Coast tick fever. The Western American dog tick is a vector of various viral and bacterial pathogens including Rickettsia rickettsii, the causative agent of Rocky Mountain Spotted Fever. These Rickettsia can cause human pathogenicity and are reportable diseases to the Centers for Disease Control and Prevention (CDC).