Covering sickness, also known as Dourine, is a chronic disease that affects horses and other types of equidae like zebras and donkeys. It is transmitted exclusively by the coitus and characterized by the progressive emaciation and edematous lesions on the genitalia. This disease often progresses rapidly and affects the nervous system.

Diagnosis is made through physical examination, blood tests, complement-fixation test and differential diagnosis.

Treatment usually involves trypanocidal drugs. However, treatment to this condition is usually not recommended because the disease may spread. Vaccination can help prevent covering disease to affect animals.

Symptoms of covering disease vary largely depending on different factors like type of virus, stress and nutrition of the infected animal. Mares develop vaginal discharge during the early stages, which could lead to the inflammation and edema of the vulva and extend to the ventral abdomen. Others develop vaginitis and vulvitis and other signs of discomfort. For virulent virus strains, abortion can occur. Stallions develop edema of the glans penis and prepuce, which spread to perineum and scrotum. Paraphimosis and persistent swelling may also occur. Genitalia ulcers or vesicles could lead to permanent scarring. Other stallions may develop keratitis and conjunctivitis. General symptoms of covering disease include incoordination, restlessness, progressive weakness, paralysis and recombency. Emaciation and anemia sometimes occur.

Covering disease is caused by a protozoan parasite named “Trypanosoma equiperdum”. Different strains of this parasite have been recorded