Synonyms
Avian tuberculosis and Avian mycobacteriosis.
Aetiology
The disease is caused by Mycobacterium avium serovars 1 and 2, Mycobacterium tuberculosis or Mycobacterium bovis may also infect birds. The organism is a non motile, non spore, alcohol and acid fast when stained with ziehl neilson stain it appears beaded. The organism is very resistant thriving in the soil for as long as 4 years.
Pathogenicity of avian tuberculosis to other mammals
Cattle-only localized infections which heal early but they are sensitive to tuberculin test.
Swine-highly susceptible resulting in progressive type of the disease.
Man-highly resistant.
Dog, cat and horses-highly resistant.
Age/species affected
All species of birds are affected which includes chickens, ducks, geese, swans, peafowls, pheasants, quails, patridges, pigeons, doves, turkeys and other feral birds. Domesticated fowl and captive feral birds are more frequently affected than those living in the wild. Mycobacterium avium affects all ages but common in birds older than one year this is because in older birds, the organisms have a greater opportunity to become established through long periods of exposure.
Transmission
The most important source of infection is the infected birds, because of the prolonged survival of Mycobacterium avium in the environment, the inanimate items contaminated by droppings of such birds are means of transmission. The tubercule bacilli in offals(intestine/respiratory tracts) create a resistant source of infection. Cannibalism also plays a part in spread of the disease in poultry.
Clinical signs
High morbidity and mortality rates are variable.
Clinical signs include
Depression and easy fatigue
Severe weight loss with atrophied pectoral muscles and breast bones becoming very prominent.
Dull and ruffled feathers.
Pale and thin comb and wattles
Diarrhea as a result of ulcerations along the intestinal tract.
Unilateral lameness and the birds walk with a characteristic hopping gait.
Sporadic death.
Post-mortem lesions
Severe emaciation
Grey to yellow nodules attached to intestine
Granulomas of various sizes in spleen, liver, bone marrow and other tissues.
Diagnosis
Tentative diagnosis is based on clinical signs and post-mortem lesions. Laboratory diagnosis is by demonstration of acid-fast organisms in smears from the liver and spleen of affected birds stained with ziehl stains.
Tuberculin test can also be used. This involves intradermal injection of the wattle with 0.03-0.05ml of purified protein derivative tuberculin from Mycobacterium avium. The injection site is monitored for reaction. Positive cases give huge edematous and painful swelling may occur within 24 hours after injection. This swelling may persist for up to one week.
Rapid plate agglutination test.
Differential diagnosis
Lymphoid leukosis, mareks aand coligranuloma
Treatment
Not recommended.
Prevention
Market birds after one laying season
Proper hygiene
Proper disposal of carcass