Lyme Disease In Washington

In order to better understand Lyme disease in Washington, the Department of Health did surveillance and established Lyme disease as a reportable condition. Tick Surveillance In April 1989, the State Laboratory began coordinating a statewide tick surveillance system. By December 1990, the State Public Health Laboratories had collected over 2,000 ticks; samples were obtained from all 39 counties. Most of the ticks (68.7%) were Dermacentor species (dog ticks), which are not competent vectors of B. burgdorferi. Eight percent were Ixodes pacificus, while 16.3 percent were Ixodes angustus (Fig. 10). Ixodes ticks are only rarely found east of the Cascade Mountains.

Fig.10 Ixodes angustus (left) and Ixodes pacificus, partially engorged. Dale Tilly.