San Mateo County: Photomicroscopy – Borrelia burgdorferi (the Lyme disease spirochete)

Entomology Report January 2008, San Mateo County Mosquito Abatement District

District staff collect and test Ixodes pacificus ticks annually to detect the presence of the Lyme disease bacterium, Borrelia burgdorferi (Bb). Ticks are dissected and their guts are split in half to perform two tests on each tick. Each tick is tested by direct fluorescent antibody (DFA) technique which involves staining tick guts with a fluorescent antibody specific to Borrelia burgdorferi. If Bb is present, the stained bacteria will appear green when viewed through a fluorescent microscope. The other half of the tick gut is placed in a culture medium that supports growth of Bb. These cultures are viewed weekly to look for live bacteria. Under dark field microscopy the otherwise clear bacteria appear white against a black background.