Glanders is a contagious disease caused by the bacteria Burkholderia mallei. Although people can get the disease, the disease primarily affects horses. It also affects donkeys and mules and can naturally infect other mammals such as goats, dogs, and cats.
Glanders is an infectious and fatal disease that mainly affects horses, donkeys, or mules caused by the bacteria Burkholderia mallei. Glands can be transmitted to humans. Sensitivity to the gland has also been demonstrated in camels, wild animals, bears, wolves, and dogs. Carnivorous animals can become infected by eating infected meat. Guinea pigs and hamsters are highly sensitive. The disease causes nodules and ulceration in the respiratory tract and lungs of animals.
A form of skin, known as ‘Persian’, is also found. In humans, the disease can take different forms such as nasal, localized with nodules and abscesses respectively, pulmonary, and septicemia, with disseminated or chronic infection. A cure is possible, however, if cases are treated quickly with antibiotics. Mortality rates are high for untreated infections. The disease has been eradicated in North America, Australia, and Europe through testing and subsequent culling of any infected animals, as well as import control measures. However, there are sporadic reports of glanders in many Asian, African, Middle Eastern, and South American countries.
Etiology of Glanders in animals
Burkholderia mallei, a clonal Gram-negative facultative intracellular obligate pathogen, is present in nasal secretions and blistered skin discharge. The gland is usually affected by:
- Eating or drinking water contaminated with nasal secretions from carrier animals
- Contact with ingredients for use
- Excretion of flesh from infected horses
The organism is sensitive to heat, light, and disinfectants. Humid, wet conditions favor survival. The polysaccharide capsule is an important factor in virulence and enhances survival in the environment.
Clinical findings of Glanders in horses and other animals
After an incubation period of 3 days to 2 weeks, animals with severe glandular infections usually:
- Septicemia
- High fever (higher than 106°F [41°C])
- Weight loss
- A thick, mucous, yellowish discharge from the nose
- Respiratory symptoms
Death occurs within a few days. Chronic disease is common in horses and is seen as a debilitating condition with nodular or ulcerative lesions of the skin and internal sinuses. Infected animals can live for years and continue to spread the organism. In some, the infection may be latent and persist for a long time.
Nasal, pulmonary, and skin glandular forms are recognized, and an animal may be affected by more than one form at a time. In the nasal form of the gland, nodules develop in the mucosa of the nasal septum and the lower parts of the turbinates. Deep ulcers have degenerating nodules with irregular borders. Characteristic star-shaped citruses remain after the ulcer heals. In the early stage, the submaxillary lymph nodes are large and edematous and later become attached to the skin or deep tissues.
In the pulmonary form of the gland, small, tubercle-like nodules with caseous or calcified centers are found in the lungs. If the disease process is extensive, consolidation of lung tissue and pneumonia may occur. Nodules may rupture and release their contents into the bronchioles, leading to the spread of infection to the upper respiratory tract.
In the glandular cutaneous form (“Persian”), nodules appear along the lymph vessels, especially of the extremities. These nodules degenerate and form ulcers that discharge highly contagious, viscous pus. The liver and spleen may also show typical nodular lesions. Histologically, vasculitis, thrombosis, and degenerative inflammatory cell infiltration may occur.
Glandular diagnosis in horses and other animals
Suspect on the basis of skin nodules with honey-like discharge or nasal discharge with ulcers on the nasal mucosa.
Common nodules, ulcers, scar formation, and emaciated conditions may provide sufficient evidence for a clinical diagnosis of the gland. However, since these symptoms usually do not develop until the disease is well advanced, specific diagnostic tests should be used as early as possible. A smear culture from the lesion confirms the diagnosis. A test for delayed hypersensitivity is performed by intrapalpebral inoculation of mullein, a secreted glycoprotein of B mallei found in the culture supernatant. Affected hypersensitive horses develop purulent conjunctivitis and eyelid swelling within 24 hours. Competitive ELISA is more sensitive than complement fixation and can be positive 3 days after infection. PCR based on 16S and 23S rRNA gene sequences can be used for specific identification.
Prevention and treatment of goiter in horses and other animals
- Detection and elimination of confirmed cases
- Treatment is contraindicated
So there is no vaccine for goiter. Protective immunity includes T-cell responses elicited by live bacteria. Prevention and control of glanders depend on early detection and elimination of infected animals, as well as thorough quarantine and strict disinfection of the area involved. Successful control depends on efforts to raise awareness among horse and donkey owners in remote areas, in addition to funding to cull infected animals. So glandular treatment does not reliably produce a bacteriologic cure. But combinations of sulfadiazine or sulfamonomethoxine with doxycycline, ceftazidime, gentamicin, streptomycin, and trimethoprim were effective in preventing and treating experimental goiter.