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Also know as: '''''Avian tuberculosis — Avian mycobacteriosis — Mycobacterium avium complex (MAC) disease — Mycobacterium avium-intercellulare complex (MAIC) disease'''''

Also know as: '''''Avian Tuberculosis — Avian Mycobacteriosis — Mycobacterium avium complex (MAC) disease — Mycobacterium avium-intercellulare complex (MAIC) disease'''''

==Introduction==

==Introduction==

Tuberculosis occurs worldwide in birds as a '''contagious, chronic, bacterial disease''' caused by members of the ''Mycobacterium avium'' complex which currently consists of four subtypes:

Tuberculosis occurs worldwide in birds as a '''contagious, chronic, bacterial disease''' caused by members of the ''Mycobacterium avium'' complex which currently consists of four subtypes:

''M. avium'' subsp ''avium'' is fully virulent for birds and small mammals.

Avian tuberculosis is a '''slowly developing disease''' that leads to anorexia, emaciation, dyspnoea and death after a few months. After being established it can '''persist in the environment and bird populations for years'''.

 

''M. avium'' subsp ''hominissuis'' is found in the environment but some are virulent in birds.

 

''M. avium'' subsp ''paratuberculosis'' affects ruminants and other animals.

 

 

Avian tuberculosis is a slowly developing disease that leads to anorexia, emaciation, dyspnoea and death after a few months. After being established it can '''persist in the environment and bird populations for years'''.

==Hosts==

==Hosts==

The disease is most commonly seen in '''older poultry''' due to the greater opportunity for infection with age.  

The disease is most commonly seen in '''older poultry''' due to the greater opportunity for infection with age.  

Game birds such as '''pheasants''' are also susceptible.

Game birds such as '''pheasants''' are also susceptible. '''Cage birds''' can also be affected by avian tuberculosis but parrots and canaries can also contract tuberculosis from ''[[Mycobacterium bovis]]'' and ''[[Mycobacterium tuberculosis]]'' species. Many species of '''wild birds''' also become infected.

 

'''Cage birds''' can also be affected by avian tuberculosis but parrots and canaries can also contract tuberculosis from ''Mycobacterium bovis'' and ''Mycobacterium tuberculosis'' species.

 

Many species of '''wild birds''' also become infected.

Amongst mammals, ''M. avium'' can cause progressive disease in '''pigs, rabbits and mink''' and cause sensitivity to the skin tuberculin test in '''cattle'''.

Amongst mammals, ''M. avium'' can cause progressive disease in '''pigs, rabbits and mink''' and cause sensitivity to the skin tuberculin test in '''cattle'''.

The disease is '''zoonotic''', although infectivity for humans is very low. The disease is progressive and often fatal and particularly severe in children and immunocompromised individuals.

The disease is '''zoonotic''', although infectivity for humans is very low. It is progressive and often fatal disease that is particularly severe in children and immunocompromised individuals.

==Spread of the organism==

==Epidemiology==

The most important source of the organism is the '''infected host'''. Also infectious are the '''items contaminated with the droppings''' of infected birds, such as litter, pastures and pens, equipment and implements, and also the hands, feet and clothing of workers.

The most important source of the organism is the '''infected host'''. Also infectious are the '''items contaminated with the droppings''' of infected birds, such as litter, pastures and pens, equipment and implements, and also the hands, feet and clothing of workers.

'''Lack of hygiene''' influences the appearance of the disease due to the organism being highly resistant in the environment. It is relatively '''resistant to many antimicrobials and disinfectants''', but sensitive to ionic detergents.

'''Lack of hygiene''' influences the appearance of the disease due to the organism being highly resistant in the environment. It is relatively '''resistant to many antimicrobials and disinfectants''', but sensitive to ionic detergents.

==Clinical signs==

==Clinical Signs==

Signs can occur for a period of weeks of months before death.

Signs can occur for a period of weeks of months before death.

'''Immunological tests''' are useful in recognising infected live birds, and include:

'''Immunological tests''' are useful in recognising infected live birds, and include:

 

:'''Tuberculin test''': In chickens, avian tuberculin is injected into the wattle, and the test read 48 hours later. The two wattles are palpated simultaneously and a positive reaction is recognised by a hot, soft and oedematous swelling in the injected wattle. Sensitivity is 80% in chickens. In other species it is not as reliable and the agglutination test is preferred.

'''Tuberculin test''': In chickens, avian tuberculin is injected into the wattle, and the test read 48 hours later. The two wattles are palpated simultaneously and a positive reaction is recognised by a hot, soft and oedematous swelling in the injected wattle. Sensitivity is 80% in chickens. In other species it is not as reliable and the agglutination test is preferred.

:'''[[Agglutination]] test''': a drop of antigen is mixed with a drop of blood from the bird and a positive reaction corresponds to agglutination within 1 minute. It has a poor specificity.

 

:'''[[ELISA testing|ELISA]]''': antibodies against ''M. avium'' can be detected in serum. A positive result can indicate previous exposure to the organism, latent infection or active infection.

'''Agglutination test''': a drop of antigen is mixed with a drop of blood from the bird and a positive reaction corresponds to agglutination within 1 minute. It has a poor specificity.

 

'''ELISA''': antibodies against ''M. avium'' can be detected in serum. A positive result can indicate previous exposure to the organism, latent infection or active infection.

==Control==

==Control==

In an outbreak, to '''eradicate and maintain freedom from infection''':

In an outbreak, to '''eradicate and maintain freedom from infection''':

 

:All infected material must be removed by '''destroying infected birds''' and thoroughly cleaning the housing and equipment.  

All infected material must be removed by '''destroying infected birds''' and thoroughly cleaning the housing and equipment.  

:Stock should only be introduced if it is free from infection: negative serological tests or absence of clinical signs.

 

:Infection should be prevented from entering the stock by '''preventing contact with wild birds''' and maintaining '''high biosecurity''' levels.

Stock should only be introduced if it is free from infection: negative serological tests or absence of clinical signs.

 

Infection should be prevented from entering the stock by '''preventing contact with wild birds''' and maintaining '''high biosecurity''' levels.

Freedom from infection should be monitored with serological testing or post-mortem investigation.

Freedom from infection should be monitored with serological testing or post-mortem investigation.

|flashcards = [[Avian Medicine Q&A 05]]

|flashcards = [[Avian Medicine Q&A 05]]

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==References==

==References==

Kahn, C. (2005) '''Merck Veterinary Manual''' ''Merck and co''

Kahn, C. (2005) '''Merck Veterinary Manual''' ''Merck and co''

[[Category:Mycobacterium_species]] [[Category:Avian Bacteria]] [[Category:To_Do_-_Bacteria]]

[[Category:To Do - Major]] [[Category:To Do - Manson]]

[[Category:Mycobacterium_species]] [[Category:Avian Bacteria]] [[Category:Alimentary Diseases - Birds]]

[[Category:Zoonoses]] [[Category:Respiratory Diseases - Birds]]