How Does Burkholderia Mallei Infect Horses? Key Signs And Risks

Burkholderia mallei is a Gram-negative, aerobic bacterium that causes glanders, a serious and often fatal infectious disease in equines (horses, donkeys, and mules).

The bacterium is primarily transmitted through direct contact with infected animals. This can occur through nasal secretions, skin lesions, or contaminated materials such as feed, water, or tack. It can also be spread by biting insects. In rare cases, humans can be infected through contact with infected animals, making it a zoonotic pathogen.

Symptoms of Equine Infection with Burkholderia mallei

Acute Form

Respiratory Symptoms: Infected horses often develop a severe cough, which may be accompanied by a thick, mucopurulent nasal discharge. The discharge can be initially clear but may become yellowish-green or bloody over time. As the disease progresses, horses may experience difficulty breathing due to inflammation and damage to the respiratory tract.

Fever: A high-grade fever is common, with body temperatures reaching 39.5–41°C (103–106°F). The fever is usually persistent and may be accompanied by chills.

Lymph Node Enlargement: The lymph nodes in the head and neck region, particularly the submandibular and retropharyngeal lymph nodes, become swollen and painful. In some cases, the lymph nodes may rupture and discharge pus.

General Malaise: Affected horses show signs of depression, loss of appetite, and reduced activity. They may become weak and lethargic, and their performance and stamina are significantly affected.

Chronic Form

Cutaneous Lesions: The most characteristic feature of chronic glanders is the appearance of skin nodules, which are usually firm and round. These nodules can be found on the legs, chest, and abdomen. Over time, the nodules ulcerate, forming deep, irregular-shaped ulcers with a granular base and a surrounding area of inflammation. The ulcers may drain a thick, yellowish-green or bloody fluid.

Respiratory Issues: Coughing and nasal discharge may persist, although they may be less severe than in the acute form. Horses may have a chronic, intermittent cough, and the nasal discharge may be less copious but still present.

Weight Loss: Despite having an appetite, infected horses often experience progressive weight loss and muscle wasting. This is due to the chronic nature of the infection, which causes a breakdown of body tissues and a decrease in nutrient absorption.

Lameness: In some cases, the infection can spread to the joints and bones, leading to lameness. The affected joints may be swollen, painful, and exhibit reduced range of motion.

It is important to note that early diagnosis and treatment are crucial for improving the chances of recovery in infected horses. In many countries, glanders is a reportable disease, and strict control measures-including quarantine and euthanasia of infected animals-are often implemented to prevent the spread of the disease.