Glanders

Description

Glanders is a contagious disease caused by Burkholderia (Pseudomonas) mallei. It exists in acute and chronic forms.

Three forms of the condition have been described; animals will show signs of one or more forms.

• Pulmonary form:

Small calcified or caseous nodules develop in the lungs, the surrounding lungs become inflammed and consolidated. The nodules may frequently degenerate to release their contents into the bronchioles which results in spread of the infection into the upper airways.

• Nasal form:

Nodules form on the nasal mucosa, nasal septum and nasal turbinates. These break down to become ulcerative with raised irregular borders, the lesions may heal to form chracteristic star shaped scars. The local lymph nodes are enlarged and as the disease progresses, they become firm and adhere to underlyinig tissues.

• Cutaneous form:

Carnivores can also be infected by ingestion of infected carcasses. The diease is zoonotic, humans are infected by inoculation through a wound and mortality is high.

Signalment

Equidae are most commonly affected, horses tend to get the chronic form and mules and donkeys the acute form. The disease was once widespread in the UK but was eradicated in 1928 and is now a Notifiable disease. Distribution is limited to parts of SE Asia, The Middle East, India, North Africa, China and Mongolia.

Diagnosis

Clinical signs may be sufficient to diagnose the condition, however they do not develop until the disease is advanced, therefore specific tests are indicated in suspected cases to aid prompt diagnosis.

Clinical Signs

Acute

• Pyrexia
• Mucopurulent nasal discharage
• Ulceration of nasal mucosa
• Coughing
• Death

Affected animals are septicaemic and die within a few days.

Chronic

• Nodular, ulcerative nasal lesions
• Subcutaneous nodules which rupure and discharge exudate
• Enlarged lymph nodes

Animals are debilitated and show clinical signs for several months, the disease may be fatal or the animal may appear to recover but it will act as a carrier and source of infection for spread of the disease.

Clinical tests

The Mallein test is used most frquently to diagnose the condition, a fraction of the causative organism is injected intradermally into the eyelid or applied as eyedrops, a positive result is seen as local swelling and discharge 1-2 days post testing.

Laboratory Tests

Other diagnostic tests include an Elisa, complement fixation and culture of the orgamism from exudative lesions.

Treatment

There is no vaccine available. Prevention and control focuses on prompt detection and slaughter of infected animals and complete quarantine and disinfection of the affected premises.

Prognosis

Prognosis is poor, the diease is usually fatal. Animals which survive should be slaughtered to prevent spread of the disease.

References

• Characterised by multiple small submucosal nasal nodules which liquefy and ulcerate
  • Cores of neutrophils surrounded by a rim of macrophages and granulation tissue
• In addition may have similar nodules in lungs, lymph nodes and cutaneous lymphatics
• Clinical signs: fever and head/ neck lymphadenitis, rhinitis

• Pathogenesis:
  • Transmited by ingestion of food/water contaminated by nasal discharge of infected Equidae; occasionally via inhalation or skin wounds
  • Organism invades nasopharyngeal mucosa and spreads to other tissues via lymphatics
  • Presence of B. mallei in host causes hypersensitivity reaction

• • Chronic disease more common:
    • Nasal form: rhinitis; ulcerative nodules develop on mucosa of nasal septum and lower part of turbinates; purulent blood-stained nasal discharge; regional lymphadenitis
    • Respiratory form: respiratory distress; granulomatous lesions throughout lungs
    • Cutaneous form (farcy): lymphangitis; nodules along lymphatic vesselsof limbs; ulcers develop and discharge pus