CRD

ChChronic respiratory Disease
(CRD) (Airsacculitis)

Cause
Mycoplasma gallisepticum

Transmission

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

Species affected
Chickens and turkeys.

Clinical signs
In chicks:
respiratory distress.
The birds frequently show a lack of appetite.
decreased weight gain and increased feed conversion ratios.
In adult birds :
sneezing,
coughing and general signs of respiratory congestion. In
laying birds a drop of egg production between 20-30 % can
occur.

Internal lesions
A reddish inflamed trachea and/or cheesy exudate in airsacs,
especially in complicated cases (e.g. with secondary E. coli
infections) are observed. In mild Mg infections the only lesion
might be slight mucus in trachea and a cloudy or light froth
in the airsacs.
Turkeys with Mg infection usually have swollen sinuses under
the eyes.
Diagnosis

Diagnosis of Mg infection can be made by blood testing of
chickens, post-mortem examination and ultimately by
isolating the causative Mg organism from tracheas or airsacs
of affected birds.

Differential diagnosis
Respiratory virus infection (Newcastle disease or infectious
bronchitis) with secondary infection (E. coli, etc.) can give
similar lesions.
Treatment
Treatment of Mg-infected chickens or turkeys with suitable
antibiotics or chemotherapeutics has been found to be of
economic value. However, control by medication or vaccination
and eradication of Mg infections has been by far the
most effective method of combating the disease. Fertile eggs
from infected birds can be treated with antibiotics such as
tylosin to eliminate the Mycoplasma gallisepticum organisms.
Methods used are the injection of fertile eggs or egg dipping.
Blood serum testing of breeder chickens for Mg antibodies
has become a routine to test flocks for a Mg infection.