Bacteria - Mycobacterium Avium

Avian Tuberculosis

1. AKA avian mycobacteriosis

2. M. avium, M intracellulare, M. genavense and others

3. MA or MAI complex (MAC, MAIC) = Mycobacterium avium intracellular infection in humans or bird

Avian TB

1. All birds can have it

   1. Especially anseriformes (duck & geese), Gruiformes (cranes) & Galliformes (chicken-types)

   2. In CAPTIVE collections most commonly

2. Not really zoonotic

   1. But young kids and immunocompromised adults can get it from the environment (not through birds)

Transmission

oral-fecal route

Signs and symptoms

Emaciation

Chronic wasting,

+/- diarrhea

Listlessness

decreased egg production

swellings around eyes

rarely respiratory signs

Much more common in adult vs young birds

Role of Stress

Stress greatly increase susceptibility

Types of stressors:

Malnutrition

Overcrowding

Drought

Extreme temperatures

Other infections

Pinioning

Sources of MAI complex

1. Ubiquitous environmental saprophyte 

2. Feces

3. Surface water (can get contaminated)

4. Soil

   1. Prefers: moist, acidic, high organic matter, contaminated with feces

5. Both wild and captive birds can be carriers (we see all three types of carriers)

Importance of Avian TB

1. Economic

   1. Disease in poultry & caged birds (& swine)

   2. Cross reactions in other LS (other types of tuberculosis tests)

      1. Cross reaction: A type of false positive reaction on a diagnostic test (similar to brucellosis suis can test positive for brucellosis arbutus) and may occur when the animal is exposed to a similar agent, was infected but has eliminated the infection (but retains antibodies), or when they are vaccinated against the agent

2. Loss of free-ranging colonies or species

   1. 18, 500 flamingos died in 1993 on 2 Kenyan lakes

Ante-mortem Dx

1. Very difficult, esp in wild birds

2. Clinical finding → clues

   1. Chronic wasting, death, emaciation, lethargy, poor quality feathers, distended abdomen (liver swelling & fluid build-up), lameness, +/- diarrhea, ocular, cutaneous or subcutaneous granulomas

3. Normal carriers → insidious Dx

   1. Subtle or hidden

4. In captive: intradermal tuberculin test, blood tests, culture

5. Wild: non practical (fecal culture?)

Post-mortem Dx

1. Liver, spleen, intestines are the best for Dx

2. Granulomas (nodules), or diffuse inflammation

3. Enlargement (liver & spleen)

4. Muscular wasting

   1. How to assess? If you can feel the bird’s keel rlly well, the bird has lost a lot of muscle

Definitive Dx

1. Necropsy: suggestive

2. Microscopic: more specific

   1. Acid-fast bacteria (acid fast test)

3. Definitive: culture or molecular identification of MAI complex bacteria

Treatment

No treatment, euthanize

Control/Prevention

1. Captive: good hygiene, ID test, remove infected birds

2. Wild: Good Luck! (Prevent contact with domestic birds?)