Glanders is a serious zoonotic bacterial disease that primarily affects horses, mules and donkeys

Etiology

Glanders results from infection by Burkholderia mallei, a Gram negative rod in the family Burkholderiaceae. This organism was formerly known as Pseudomonas mallei. It is closely related to and appears to have evolved from the agent of melioidosis, Burkholderia pseudomallei.

Transmission

Glanders is mainly transmitted by contact with skin exudates and respiratory secretions from infected equids. Latently infected as well as clinically ill animals can spread the disease. Horses, mules and donkeys often become infected when they ingest B. mallei in contaminated food or water. This organism can also be spread in aerosols, and by entry through skin abrasions and mucous membranes. Humans are infected by contact with sick animals, contaminated fomites, tissues or bacterial cultures. Transmission is often through small wounds and abrasions in the skin. Ingestion or inhalation can also occur.

Clinical Signs

Horses, donkeys and mules

In equids, glanders is traditionally categorized into nasal, pulmonary and cutaneous forms. In the nasal form, deep ulcers and nodules occur inside the nasal passages, resulting in a thick, purulent, yellowish discharge. This discharge may be unilateral or bilateral, and can become bloody. Nasal perforation is possible. The regional (submaxillary) lymph nodes become enlarged and indurated, and may suppurate and drain. Healed ulcers become star–shaped scars. In the pulmonary form, nodules and abscesses develop in the lungs. Some infections are inapparent; others vary from mild dyspnea to severe respiratory disease. In more severe cases, the clinical signs include coughing, dyspnea, febrile episodes and progressive debilitation. Diarrhea and polyuria may also be seen. Discharges from pulmonary abscesses can spread the infection to the upper respiratory tract. In the cutaneous form, the skin contains nodules that rupture and ulcerate, discharging an oily, purulent yellow exudate. The regional lymphatics and lymph nodes become chronically enlarged; the lymphatics are filled with a purulent exudate. In addition, there may be swelling of the joints and painful edema of the legs. Glanderous orchitis is a common symptom in males

Treatment

Treatment is risky, as infections can spread to humans and other animals, and treated animals can become asymptomatic carriers.