Mange is an intensely itchy skin disease caused by four different genera of parasitic mites---Chorioptes, Demodex, Psoroptes, and Sarciotes. Mites are microscopic acarids that live on or in, and feed off of, the skin of their host. The mites' presence cause intense irritation as they burrow into the horse's skin, feeding on the exfoliated skin cells. This irritation causes severe itching, hair loss, and the formation of scabs and lesions. The lesions develop either as a result of the intense itching, secondary infection, an immunologic hypersensitivity to the foreign antigens of the mites, or from secretion of the irritant substances by mites. Different species of mites are known to affect specific areas of the horse's body.

Mange is further classified into subgroups, depending on the specific type of mite.

• Chorioptic mange: This is one of the most common forms of mange seen in horses, especially draft horses. It is also referred to as tail manage, foot manage, and leg manage. Chorioptic manage is caused by invasion with the Chorioptes bovis mite. C. bovis has a short life cycle, of 2-3 weeks, and are able to survive off of their host for two months or longer. They are found most often during the winter months, in animals that are stabled in barns. These mites are most often found on the lower legs (fetlock and pastern), tail and anal area of the horse.
• Demodectic mange: This type of mange is caused by two different species of mites---D. caballi which invades the eyelids and muzzle area of the horse, and D. equi, which manifests as folliculitis on the body. This type of mange is considered rare in horses, and usually only a problem for horses that are severely immunosuppressed.
• Psoroptic mange: Psoroptic manage is caused by two different mites---P. equi and P. cuniculi. This form of mange is associated with the presence of generalized dermatitis and otitis (inflammation or infection of the ear). Mites are found throughout the main parts of the horse's body (withers, mane, shoulders and flank) or within the ear.
• Sarcoptic mange: Sarcoptic mange is caused by invasion by Sarcoptes scabiei var. equi mites in the horse. Female mites will burrow into the top layers of the skin, feeding on the tissue fluids. These mites often tend to stay on the head and neck. S. scabiei are usually found on pigs, goats, and cattle; they rarely invade horses.

Transmission
Mites are transmitted to horses usually from direct contact with an infected wild animal, other horse, or domestic companion animal. Less common ways mites are transmitted is indirectly from contamination of the environment, equipment, fomites or humans.