Respiratory Disease

Chronic Respiratory Disease (CRD)

[Chronic Respiratory Disease is an advance] manifestation of Mycoplasma gallisepticum, one of the species of mycoplasma that, as primary pathogens, can cause acute and chronic diseases at multiple sites, with wide-ranging complications (1).


There is evidence of egg transmission of CRD, and many authorities believe that the infection lies dormant in the chickens until a stress factor , such as a sudden change in environment , disease, or a vaccination reaction, triggers an outbreak of disease (2).

This is why it is relatively common for unvaccinated gamecock develops this disease whenever they are conditioned for battle.

The main problem is that parent birds infected with Mycoplasma gallisepticum can transmit the organism through the egg to their offspring (vertical transmission). In addition, infection can occur by contact or by airborne dust or droplets (horizontal transmission) (3).


Familiar respiratory signs are difficulty breathing, nasal discharge and rattling in the windpipe. Feed consumption drops off, and birds soon become weak and thin, with many razor-blade breasts appearing in advance stages of CRD (2). The face may swell as well.


Prevention by vaccination is effective in most farms. Management of stress and monitoring for signs is also a great in controlling the disease.


Mycoplasma gallisepticum is known to be susceptible to several antibiotics, including macrolides, tetracyclines, fluoroquinolones, but is resistant to penicillins or other antibiotics which act by inhibiting cell wall biosynthesis (1). Treatment … with suitable antibiotics… has been found to be of economic value, but will not eliminate MG from the flock (3).

See Antibiotic Families for the list of antibiotics that you may use to rotate.

Totalgamefowl Approach

The totalgamefowl primary approach to deal with mycoplasma gallisepticum is vaccination using live vaccine. Vaccination are complemented with stress management and monitoring for signs resulting to controlling the disease with no difficulty.

Because the symptoms of Mycoplasmosis is similar to coryza and differentiation sometimes may not be plausable, antibiotics that deals with both disease is used such as tylosin or erythromycin and rotated by enrofloxacin.


For differentiation with mycoplasma and coryza, it is good to perceive mycoplasma is as already present in dormant state and triggered with stress and commonly occurs in hot summer season whereas coryza is triggered in wet season by poor litter management.

Immune Boosters

Added to this, as stated by Levisohn & Kleven (2000), Resistance to the clinical manifestations of mycoplasma infection, and positive response to antibiotic therapy for disease require an intact immune system, immune boosters are added to the treatment activity, and those do not heal after the shifting of antibiotics are culled as this implies the immune system of the gamefowl is compromised.


  1. Levisohn, S. & Kleven, S. H. (2000). Avian Mycoplasmosis (Mycoplasma gallisepticum) Rev. sci. tech. Off. int. Epiz., 19(2). p 426
  2. Dr. Salsbury’s Laboratories. Dr. Salsbury’s Manual of Poultry Diseases. Charles. p 8
  3. MSD Animal Health (2013). Important Poultry Diseases – Keep up the defense. Whitehouse Station: Intervet International B.V.. p 27

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