Description

Caused by the protozoal parasite Trypanosoma equiperdum, this serious, often chronic venereal disease can result in neurological damage and emaciation, and although clinical signs may appear within a few months of infection, it is often not evident until after several years. Dourine is typically a disease of horses and donkeys, although zebras have tested positive for the disease.

Once widespread, this disease has been eradicated in most countries. Presently, it is found in most of Asia, southeastern Europe, South America, and in northern and southern Africa.

This venereal disease is spread almost exclusively by coitus from Trypanosoma equiperdum organisms in the urethra of infected stallions and in vaginal discharges of infected mares.

Dourine is characterized by stages of exacerbation, tolerance, and relapse that vary in duration and may recur several times before death or recovery.

Symptoms

• Vaginal discharge in mares
• Swelling and edema of the vulva
• Vulvitis and vaginitis
• Signs of discomfort, such as an elevated tail
• Anemia
• Conjunctivitis
• Variable edema of the prepuce and glans penis in stallions
• Paraphimosis
• Ulcers or vesicles on the genitalia that leave white scars when healed
• Nervous disorders, including restlessness and shifting of weight from leg to leg
• Progressive weakness
• Paralysis and recumbency

Causes

Dourine is a chronic trypanosomal equine disease. Dourine is caused by infection with the protozoal parasite Trypanosoma equiperdum, related to T brucei, T rhodesiense, and T gambiense. This parasite can periodically replace its surface glycoprotein antigen and evade immune responses. Strains vary in pathogenicity.

Prevention

Successful prevention focuses on serologic identification of infected animals. Since treatment is not recommended for fear of inapparent disease carriers, infected animals should be humanely destroyed or castrated to prevent further transmission of the disease.

All horses in an area where dourine is found should be quarantined, and breeding should be stopped for one to two months while testing is continued.

Treatment

Treatments with trypanocidal drugs such as suramin and quinapyramine dimethylsulfate have been reported to be successful, especially when the disease is caused by the more virulent (European) strains of the parasite.

Because of the fear of creating asymptomatic carriers, treatment is not recommended in dourine-free areas. Estimates of the mortality rate range from 50% to nearly 100%. Apparent recoveries have been questioned because of the waxing and waning of symptoms.