Avian Tuberculosis (TB) in Laying H ...

Avian Tuberculosis (TB) in Laying Hens

Avian Tuberculosis (TB) in Laying Hens

Happenings / Clinical Signs

Clinical signs are not pathognomonic

Visibly sick birds

  • Birds will be less lively than its pen mates
  • Birds will fatigue easily
  • Birds may be depressed
  • Progressive and striking loss of weight commonly occurs
  • Atrophy of breast muscles with prominent keel
  • The face of affected birds appears smaller than normal


  • Low mortality or increases gradually
  • Affected birds may die within a few months  or live for many depending on severity or extend  of the disease

Dead Birds

  • Poor body fleshing condition

Head Comb Wattles Face Nostrils Sinuses Mount Beak Ear lobes

  • Comb, wattle and earlobes often appear pale and thinner than normal and have dry epidermis
  • Occasionally, the comb and wattles have a bluish discoloration
  •  Icterus of the comb and wattles is an indicative of advance hepatic damage may be noted

Neck wings breast abdomen shanks legs hocks feet joints vent skin

  • Atrophy of breast muscles with prominent keel

Lameness or unusual movement, incoordination, ataxia

  • In many instances, the birds reveals and unilateral lameness and walks with peculiar jerky hopping gait

Feather Abnormalities

  • Feathers assume a dull and ruffled appearance

Avian Tuberculosis is diagnosed rarely in commercial poultry. It has been diagnosed in small flocks and in relatively small free-range commercial flocks.

Avian Tuberculosis (TB) is a contagious disease and chronic infection. Persistence in a flock, once established, induce unthriftiness and finally causes death. Clinical signs are not pathognomonic. In advanced infections, the bird will live for a shorter period of time than its pen mates, so it may trigger them fatigue easily and possible depression. Although appetite usually remains good, progressive and striking loss of weight commonly occurs. Feathers assume dull and ruffled appearances. Comb, wattles and earlobes often appear pale and thinner than normal and have a dry epidermis. Occasionally, the comb and wattles have a bluish discoloration. In many instances, the bird reveals a unilateral lameness and walks with a peculiar jerky hopping gait. Paralysis from tuberculous arthritis can sometimes occur. There is often persistent diarrhea with soiling of the tail feathers. Avian tuberculosis appears to be less prevalent in younger birds.

Causing Agents
Bacterial Infection. Mycobacterium avium serovars 1,2 and 3. Mycobacterium avium serovar 2, the organism most frequently isolated from chickens is rarely isolated from humans.
Affected Systems/Organs
Digestive and Locomotor System. Various organs and tissues. Bones and joints.
Transmission bird to bird. Droppings. Objects or items contaminated with droppings.
Mainly Affects
Quarantine. Biosecurity, Hygiene. Disinfection and anything that might be contaminated by their excretions or faeces.
Suggested Actions
  • Can be confirmed with clinical signs and gross lesions
  • Technical assistance recommended
  • Diagnosis should be confirmed with rapid assays and/or a certified laboratory
  • Veterinary intervention is recommended
  • Can be managed with vaccination programs.
  • This is a notifiable disease, veterinary intervention is essential. It is advisable that you run DTECT again to ensure you have answered all the questions correctly. If you suspect that you may have this disease please contact your local authorities immediately.

Impact on Egg quality


Impact on Liveability


Impact on Production


Overall Economic Impact


Y.M. Saif.2008.Disease of Poultry. 12th Edition. page 944

David E. Swayne. 2013. Diseases of Poultry 13th Edition. page 1012


Mark Pattison, Paul F. McMullin, Janet M. Bradbury. Dennis J. Alexander. 2008. Poultry Diseases. 6th Edition.

Paul McMullin. 2004. A pocket Guide to Poultry Health and Disease. First Edition.

Steven Leeson, John D. Summers. 2008. Commercial Poultry Nutrition. Third Edition.

Donald D. Bell, Williams D. Weaver. 2009.  Commercial Chicken Meat and Egg Production. Fifth Edition.

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