ABSTRACT
Ticks are bloodsucking ectoparasites that are efficient vectors of several different types of disease agents such as bacteria, protozoans, and viruses. In fact, they are second only to mosquitoes as arthropod vectors of human disease. In addition, tick bites cause a variety of acute and chronic skin lesions. Lyme borreliosis, caused by the bacterial spirochete Borrelia burgdorferi, is a systemic tick-borne illness with many clinical manifestations that occurs over much of the world in temperate zones. Ticks may transmit a wide variety of rickettsial organisms to humans and other animals. The spotted fever group contains rickettsial species related to the agent of Rocky Mountain spotted fever, Rickettsia rickettsii, but there are many other rickettsial species in the spotted fever group; it contains at least 11 disease agents and 15 others with low or no pathogenicity to humans.
