It is thought that mycoplasmas damage the local defence mechanisms in the respiratory tract eg damage the cilia, thin mucous secretions and also may have a mild immunosuppressive effect. This increases the sensitivity of the bird to respiratory virus infections such as infectious bronchitis, infectious laryngotracheitis, Newcastle Disease and avian pneumovirus. Mycoplasmas may also cause birds to react to live virus vaccines. The physical damage to the defensive cilia also enables bacteria to penetrate deep into the respiratory tract, especially E. coli, which causes coli-septicaemia or complicated CRD (CCRD). The bacteria penetrates deep into the lung and air sac and can penetrate into the blood stream causing severe peri-hepatitis, peritonitis and pericarditis, which may lead to the bird’s death or often condemnation at slaughter.
Other bacterial infections, such as Haemophilus paragallinarum (coryza), Pasteurella multocida (cholera) and Ornithobacterium rhinotracheale, also benefit from mycoplasmal infection or mixed mycoplasmal/viral damage and penetrate the respiratory tract more easily.
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Mycoplasmas colonise respiratory
tract . . . |
damage cilia and cells . . . |
and allow E. coli to invade |
Colibacillosis
(Colisepticaemia) |
 Mycoplasma  E. coli |
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Tiamutin – targeting mycoplasmas
Tiamutin + Tetracyclines for mixed infections
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