Sacramento-Yolo Counties Lyme Disease Surveillance 2005

Annual Report 2005, Sacramento-Yolo Mosquito and Vector Control District

Summary of Sacramento-Yolo MVCD 2004—2005 Tick Surveillance Data

Location          Total   Pools    Positive   Estimated Minimum
                  Ticks   Tested   Pools      Infection Rate
Yolo
Cache Creek        257      23         3              1.2%
Sacramento
Ancil Hoffman        0       0         0              N/A
Mississippi Bar     66      12         1              1.5%
Negro Bar           19      13         0              0.0%
Nimbus Dam          38       9         2              2.7%
Snipes Park         68      13         0              0.0%
Willow Creek        46      10         0              0.0%
Total              494      80         8

The bacterium that causes Lyme disease is called Borrelia burgdorferi. The primary vector for Lyme disease for Sacramento and Yolo Counties is Ixodes pacificus, also known as the western black—legged tick. The table... summarizes the Lyme disease surveillance data of Ixodes pacificus ticks collected from November 2004 through May 2005.

Tick specimens were collected by dragging a flannel sheet along the side of a trail, a technique called flagging. The ticks were pooled and tested by indirect immunofluorescence assay (IFA). A sample was considered positive by IFA if one or more fluorescently stained spiral—shaped bacteria were present. Some positive samples were confirmed using a polymerase chain reaction assay and by culture in liquid media.

San Mateo County: Tick Surveillance

Entomology Report June 2005, San Mateo County Mosquito Abatement District

The District has begun conducting surveillance for Rocky Mountain spotted fever (RMSF) in conjunction with state and county health department personnel. This disease is caused by the bacteria Ricketsia rickettsii and transmitted by ticks. Symptoms of the disease include sudden onset of fever, headache, and muscle pain, followed by development of a rash. Two residents of San Mateo County have been diagnosed with spotted fever group rickettsia in the past 3 years. The disease can be transmitted by 2 species of ticks found locally (Dermacentor variablis and Dermacentor occidentalis). Therefore, surveillance is being conducted to assess the public health risk in the county for RMSF. Unlike the western black-legged tick (vector of Lyme disease), these ticks are active during summer months.

Over 100 ticks were collected from Sawyer Camp trail and Edgewood Park in June and are currently being tested by CDHS for spotted fever group rickettsia.