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Avian Tuberculosis

Mycobacteriosis

Avian Tuberculosis Overview

Avian tuberculosis (ATB) is an infectious, contagious bacterial disease caused by organisms of the Mycobacterium avium complex (MAC) that affects all avian species, especially waterfowl. MAC consists of M. avium subsp. avium, M. avium subsp. paratuberculosis, M. avium subsp. Silvaticum, and M. intracellulare. ATB presents as a chronic and progressive disease course, with affected birds showing gradual and eventually marked weight loss, weakness, and general unthriftiness in their overall appearance. In birds, ATB primarily targets the liver and digestive tract, and later disseminating into the lungs, air sacs, spleen, bone marrow, and skin. Ducks that are stressed or have poor immune systems are more susceptible to infection with Mycobacterium spp. ATB is common in captive waterfowl kept in zoos.

Transmission
The main source of infection for ducks is by exposure to the same environment as infected birds. This is because infected birds will shed large amounts of the organism in their feces, contaminating their environment. Since Mycobacterium spp are highly resistant, they can survive in soil for up to 4 years, making it difficult to eradicate from contaminated environments. Ducks become infected through ingestion or inhalation of the bacteria while dabbling in their environment.

Incubation period
ATB has a long incubation period and a slow course, with symptoms prolonging in ducks for weeks or months.

Symptoms

Weight loss
Marked atrophy of breast muscles
Lameness
Depression
Poor body condition
Weakness
Diarrhea
Enlarged abdomen
Reduced egg production

Diagnosis

  • History
  • Clinical signs
  • Acid fast staining
  • Bacterial culture
  • Tuberculin test
  • Rapid agglutination test
  • ELISA
  • PCR
  • Necropsy gross lesions

Treatment

MethodMethod Summary
Antibiotic sensitivity testingIndicated for treatment, since each strain of M. avium shows differing resistance to different antibiotics.
Supportive care

Prevention

  • Reduce stress
  • Biosecurity
  • Do not use peat as a bedding material for ducks
  • Minimizing overcrowding
  • Providing proper ventilation
  • Supplementing adequate amounts of vitamins and minerals in diet
  • Quarantine new birds to the flock for at least 60 days

References

Age Range

It usually occurs in birds over 2 years of age but can occur in birds of all ages.

Risk Factors

  • Stress
  • Exposure to wild bird populations, including sparrows, starlings and pigeons
  • Roof-harvested rainwater
  • Living in the North Temperate Zone
  • Overcrowding
  • Poor sanitation and hygienic conditions
  • Kept in captivity