Avian Tuberculosis (Mycobacterium avium): Granulomatous Pathology
Veterinary guide covering Mycobacterium avium subsp. avium, acid-fast granulomas, emaciation, and flock depopulation.
Scientific Overview
Avian Tuberculosis is a chronic, contagious bacterial disease of mature poultry, game birds, and wild birds caused by Mycobacterium avium subsp. avium. Characterized by progressive emaciation, extreme muscle wasting, lameness, and widespread granulomatous nodular lesions (tubercles) in visceral organs.
Etiology & Acid-Fast Cell Wall Stability
Avian Tuberculosis is defined as a chronic granulomatous disease caused by Mycobacterium avium subsp. avium (serotypes 1, 2, and 3), an acid-fast non-motile rod bacterium with a high mycolic acid cell wall content.
The high lipid cell wall makes M. avium exceptionally resistant to environmental disinfectants, acid/alkali conditions, and drying, persisting in soil for over 4 years.
Pathology: Acid-Fast Granulomas (Tubercles)
Gross necropsy findings in old laying hens or free-range stock:
- Visceral Tubercles: Greyish-yellow, firm, fibrous granulomatous nodules of varying size scattered throughout the liver, spleen, intestines, and bone marrow.
- Extreme Emaciation: Severe knife-like atrophy of the pectoral breast muscles ('going light') despite normal appetite.
- Ziehl-Neelsen Staining: Microscopic impression smears of tubercle centers stained with Ziehl-Neelsen demonstrate massive clumps of bright red acid-fast bacilli.
Control & Eradication Strategy
Treatment is ineffective and prohibited due to antibiotic resistance risks. Eradication requires complete depopulation of infected flocks, thorough litter removal, topsoil replacement in outdoor runs, and restocking only all-in/all-out pullet housing systems.
Avian Tuberculosis (Mycobacterium avium): Granulomatous Pathology — Frequently Asked Questions
Related Pathologies & Differential Diagnosis
Differential diagnostic screening: Cross-reference clinical lesions and flock symptoms against these closely associated avian pathologies:
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