Ticks and Lyme Disease in Contra Costa County 2005

2005 Annual Report, Contra Costa County Mosquito And Vector Control District

Tick Testing

Bollinger Canyon Rd, San Ramon Site
A total of 670 adult Western black-legged ticks were collected from the Bollinger Canyon Road site 1A this season. Seventy four ticks were tested (45 females, 29 males) for the presence of Lyme disease, using an Indirect Fluorescent Antibody test (IFA). Two of the seventy-four ticks tested were found to be positive for the Lyme disease, yielding a 2.7 percent infection rate. This is the twelfth season for which ticks have been tested from this site. The average infection rate over the twelve year period is 3.71 percent, which is slightly higher than the Californian State average of 2.0 percent. The chart below shows the Lyme disease (B. burgdoferi) infection rate at the Bollinger Canyon Site between the 1993-94 to 2004-05 seasons.

Springhill Rd, Lafayette Sites
In addition to our regular Lyme disease IFA testing, a total of 374 adult Western black-legged ticks were collected from five sites near Springhill Road, Lafayette, and were tested using real-time PCR by Dr. Alan Barbour of University of California, Irvine, for the presence of two species of Lyme disease causing bacterium, Borrelia burgdorferi and Borrelia miyamotoi. Borrelia miyamotoi is closely related to B. burgdoferi, but at this time has not been shown to cause disease in humans. This location was chosen as it was an area previously known to have had high Lyme disease infection rates in Western black-legged ticks that were collected by both Contra Costa Mosquito & Vector Control staff and those submitted by the public to our office for testing. The infection rates have varied yearly from 0-14 percent.