Sheep tick (Ixodes ricinus). Light micrograph of a common sheep tick showing the modified palps and chelicerae which suck blood (top). It has eight legs with hooked claws like grappling irons, the first pair being sunk into the skin. The tick is a type of arachnid ectoparasite and is common in the damp underbrush of European woods. It attacks both domestic and wild animals, including dogs and humans. The tick carries the spirochaete bacterium Borrelia burgdorferi, which causes both Lyme disease and a closely- related disease known as erythema migrans. Both diseases cause skin lesions, neurological and cardiac abnormalities, and recurrent arthritis.