Lyme disease. Coloured scanning electron micrograph of the spirochaete bacterium Borrelia burgdorferi in the midgut lumen (cavity) of an infected tick. The spiral-shaped bacteria (the long, worm-like objects) are passed on to humans via tick bites and cause Lyme disease. Symptoms include skin lesions, neurological and cardiac abnormalities & recurrent or chronic arthritis. Several species of tick have so far been found to harbour the bacteria, but the principal vectors are thought to be Ixodes ricinus, in Europe and I. dammini and I. pacificus in North America. Magnification: x4, 300 at 6x7cm size. x15,000 at 8x10 inch size.