Lyme disease bacteria. Coloured scanning electron micrograph (SEM) of a conglomeration of Borrelia burgdorferi bacteria, cause of Lyme disease in humans. These spiral-shaped spirochaete bacteria are here coloured yellow. They are passed on to humans by tick bites, commonly Ixodes ricinus in Europe and Ixodes pacificus in North America. The ticks can infest domestic dogs. Symptoms of Lyme disease include skin lesions, muscle pain, neurological and cardiac abnormalities, and arthritis. Treatment includes antibiotic and corticosteroid drugs. Magnification unknown.