Besnoitiosis is a protozoan disease of the skin, subcutis, blood vessels, mucous membranes, and other tissues. The causal agent of the cutaneous disease is Besnoitia besnoiti in cattle and B. bennetti in horses and donkeys. B. jellisoni and B. wallacei have been described from rodents; B. tarandi from reindeer or caribou; B. darlingi from lizards, opossums, and snakes; and B. sauriana from lizards. Bovine besnoitiosis is either a severe disease of cattle, or a mild clinical disease. The severity of the disease may vary between mild and severe cases and even death of seriously affected animals.