Tuberculosis

INTRODUCTION Tuberculosis of poultry, often termed avian mycobacteriosis, avian tuberculosis, avian TB or TB, is a contagious disease caused by Mycobacterium avium. Avian tuberculosis is a chronic infection. Persistence in a flock once established, induces unthriftiness, decreased egg production, and finally causes death.

Age of Host Commonly Affected Avian tuberculosis appears to be less prevalent in young fowl not because the younger birds are more resistant to infection, but because in older birds the disease has had a greater opportunity to become established through a longer period of exposure.

Transmission The contaminated environment, especially soil and litter, is the most important source for the transmission of the bacilli to uninfected animals. The longer the premises have been occupied by infected birds and the more concentrated the poultry population, the more prevalent the infection is likely to be. M. avium may persist in soil for up to 4 years.

Clinical Signs Clinical signs are not pathognomonic. In advanced infections, the bird will be less lively than its pen mates, will fatigue easily, and may be depressed. Although appetite usually remains good, progressive and striking loss of weight commonly occurs, evident as atrophy of breast muscles with a prominent keel.

With advanced emaciation, nodular masses can be palpated along the intestine. However, the hepatomegaly that many tuberculous birds possess may make this procedure difficult or impossible. Intestinal nodules may be ulcerative, resulting in severe diarrhea. Affected birds may die within a few months or live for many, depending on severity or extent of the disease. A bird may die suddenly as a consequence of hemorrhage from the rupture of the affected liver or spleen.

DIAGNOSIS Gross lesions Isolation and identification Tuberculin Test Serology

Differential Diagnosis These include coligranulomas (Hjarre’s disease), pullorum disease, other salmonella infections, enterohepatitis, fowl cholera, and neoplasia.

INTERVENTION STRATEGIES Management Procedures Vaccination Use of experimental vaccines containing inactivated and/or live mycobacteria for protecting chickens against tuberculosis has been evaluated

Treatment Treatment with antituberculosis drugs is impractical and is rarely done to treat domestic backyard poultry. However, combinations of antituberculosis drugs have been used to treat certain exotic birds maintained in captivity

Positive reaction in the left wattle of tuberculous chicken 48 hours after intradermal injection of avian tuberculin.

Tuberculous lesions in liver and spleen