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CRD/Mycoplasma Gallisepticum (MG)

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1CRD/Mycoplasma Gallisepticum (MG) Empty CRD/Mycoplasma Gallisepticum (MG) on Wed Feb 15, 2012 10:06 am


Golden Member
Golden Member
I have been doing some research into common illnesses that one could choose to guard against through vaccination. I thought it would be handy to have a thread dedicated to some of these.

Mycoplasma is way up there in the list of common poultry diseases. I have seen posts on other forums where people say "my chicken is sneezing and I think she has a cold". I guess it would be more correct to say she has CRD.

Chronic Respiratory Disease
(CRD) (Airsacculitis)

The underlying cause of CRD is Mycoplasma gallisepticum
. The condition is frequently triggered by respiratory viruses
such as ND and IB and subsequently complicated by bacterial
invasion. The main agents involved in the infection are
Mycoplasma gallisepticum and E. coli. Stress caused by
moving the birds, by debeaking or other operations or other
unfavorable conditions e.g. cold or bad ventilation, make the
birds more susceptible.

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. The incubation
period varies from 4 days to 3 weeks.
Species affected: Chickens and turkeys.

Clinical signs
Young chickens (broiler chicks or layer pullets) will show
respiratory distress. The birds frequently show a lack of
appetite, decreased weight gain and increased feed conversion
In adult birds the most common symptoms are sneezing,
coughing and general signs of respiratory congestion. In
laying birds a drop of egg production between 20-30 % can
CRD does not normally cause an alarming number of deaths.
The effect is more of a chronic nature causing reduced weight
gain and feed conversion ratios in broilers and lower egg production
in breeders and layers. In this way the overall economic
loss can be very great in broilers but less dramatic in
breeders and layers.

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 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 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.

Pericarditis, peritonitis and
perihepatitis is frequently observed
in birds with CRD

This information copied from:

Last edited by KathyS on Wed Feb 15, 2012 10:12 am; edited 1 time in total (Reason for editing : Edited to add source of info: canadianpoultry.ca)


3CRD/Mycoplasma Gallisepticum (MG) Empty Re: CRD/Mycoplasma Gallisepticum (MG) on Thu Jun 28, 2012 9:15 am

Omega Blue Farms

Omega Blue Farms
Full Time Member
Full Time Member
Thanks for posting, the following is new to me.

"Fertile eggsfrom 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."

Rather than dispose of my Malay flock for being 100% susceptable to CRD and/or Coryza, I've found an opportunity to breed for resistance. While I travel this path, a generation or two of egg dipping may become a valuable tool. Does anyone know if a similar option is available for Coryza?


4CRD/Mycoplasma Gallisepticum (MG) Empty Re: CRD/Mycoplasma Gallisepticum (MG) on Thu Jun 28, 2012 9:41 am

Country Thyme Farm

Country Thyme Farm
Full Time Member
Full Time Member

This site claims that tylosin is effective against Coryza, but also says that the disease is not egg transmitted...you'll probably want to do some further research, but it's a start.


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