Infection with Burkholderia mallei (Glanders)

Disease is described by the site of the main lesions, and cases often combine forms. Nasal glanders starts with high fever, inappetence and laboured breathing with cough, then a sticky yellow-green discharge that crusts at the nostrils, nodules and ulcers on the nasal mucosa, and hard, enlarged submaxillary lymph nodes. Pulmonary glanders brings cough, dyspnoea and progressive weight loss. The cutaneous form (farcy) develops slowly with chains of skin nodules along lymphatics, mainly on the inner thighs, limbs and abdomen, which rupture to discharge thick yellow pus and heal poorly. Healed nasal ulcers leave star-shaped scars.

Glanders is caused by Burkholderia mallei, a Gram-negative, non-motile, non-spore-forming rod closely related to the melioidosis agent, B. pseudomallei. The bacterium enters through ingestion, inhalation, skin abrasions or mucous membranes and replicates inside host cells, which helps it evade some antibiotics. It forms pyogranulomatous nodules that ulcerate or caseate. In the nasal passages these become ulcers that can perforate the septum; in the lungs they progress from small haemorrhage-rimmed nodules to caseous or calcified foci that discharge into the airways; in the skin they follow the lymphatics, which thicken into cords. Nodules also seed the liver, spleen and kidneys. Acute disease kills quickly, whereas chronic and latent infection wears the animal down over months.

Horses, mules and donkeys are the primary hosts; donkeys are most susceptible and horses tend to develop chronic disease. Dromedary camels kept close to infected horses, cats and big cats, and carnivores that eat infected meat also contract it. The disease is endemic in parts of the Middle East, Asia, Africa and South America, and Bahrain reported its first occurrence in 2010; it has been eradicated from North America, Western Europe and Australia. Spread is mainly by ingesting feed or water contaminated by nasal or skin discharges, and by shared troughs, harnesses and grooming tools; subclinical carriers matter more than clinical cases. It is zoonotic, chiefly a risk to laboratory and equine workers, and is WOAH-listed and reportable.

WOAH lists strangles, ulcerative lymphangitis, botryomycosis, sporotrichosis, epizootic lymphangitis, tuberculosis, trauma and allergy, and warns that clinical signs alone cannot confirm glanders, especially early or latent cases. Melioidosis resembles it clinically, and serology can cross-react with B. pseudomallei and environmental Burkholderia. Separation therefore depends on isolating B. mallei by culture, ideally from unruptured nodules, supported by PCR and serology.

Nasal mucosa, upper respiratory tract, lungs, submaxillary and other lymph nodes, lymphatic vessels, skin and subcutis, liver, spleen, kidneys, testes

No vaccine. Test and humanely eliminate reactors, screen healthy equids, control movement and quarantine premises, disinfect equipment and destroy feed and bedding, avoid communal troughs, import serology, never feed equid meat to animals.

Acute glanders is usually fatal within days to weeks; chronic cases may survive for years while shedding. Case fatality can reach 95% untreated. Treatment is allowed in few endemic areas and may leave carriers, so positives are usually euthanised.