Clinical Signs of Mycoplasma CRD:
- Most characteristic signs are tracheal rales
- Nasal discharge & coughing
- Reduced feed consumption
- Weight loss
- Egg production declines but maintained at lower level
- Serologically positive without clinical signs (because of infection occurs at younger age)
- Male birds are affected severely than females
- Disease is more severe in winters
- In broilers – most outbreaks at 4 week of age, frequent well marked signs
- High mortality and morbidity in broilers, esp when other concurrent infection occurs like IB or E.coli
- Visibly conjunctivitis and keratoconjunctivitis, swelling of facial skin, lacrimation are often seen
- Infection may affect all the chickens in a flock
- Disease become more severe and longer in winters
- Young birds are affected more than older
- Loss of egg production is most often seen
- Primary cause of CRD, often combined with other pathogens which results in complications
- In field severe air sac infection is seen which is designated as CRD. Its main cause is Mycoplasma gallisepticum
- ND and IB precipitates Mycoplasma gallisepticum outbreaks
- E. coli causes severe complications
- It has been ruled out tha E. coli do not effect air sacs unless it is previously infected with MG or IB/ND
- E. coli + Infectious Bronchitis + Mycoplasma gallisepticum = very severe outbreaks (airsacculitis) of CRD and CCRD
- Mortality in adults flock is negligible but egg production declined
- Mortality in broilers varies from very low in non-complicated cases to 30% in complicated cases (esp. in colder months)
Pathology of Mycoplasma CRD:
- Catarrhal exudate in nasal, paranasal sinus, trachea, bronchi and air sacs.
- Sinusitis is commonly seen
- Air sacs contain yellow color caseous cheezy exudate
- In severe cases of air sac disease – triad of air sacculitis, fibrinous or fibrinopurulent perihepatitis & adhesive pericarditis results in severe mortality. But one should be careful as these signs are also seen in chlamydiosis or septicaemia
- Commercial layer Mycoplasma gallisepticum causes keratoconjunctivitis which often seen with facial edema and corneal opacity
- Distended oviducts with marked inflammation (salpingitis) in layers and breeders
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