Pathology of Mycoplasma Gallisepticum Infection in Laying Chicken
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Date
2015
Authors
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Publisher
TANUVAS, Chennai
Abstract
The prevalence and pathology of Mycoplasma gallisepticum and its
combined pathogens among laying chicken in Namakkal region was studied.
Sixty five commercial layer farms situated in and around Namakkal region with
the history suggesting Mycoplasma gallisepticum infection were investigated for
a period of one year (May 2014 to April 2015). Out of these, 36 farms were
positive for MG and these occurred in different combinations of pathogens. Out
of 36 farms, Mycoplasma gallisepticum alone was detected in 8 farms (22.22 per
cent). The remaining 28 farms (77.78 per cent) were affected by MG with
different combinations of concurrent infections like Escherichia coli, Avibacterium
paragallinarum, Pasteurella multocida and Ornithobacterium rhinotracheale. The
highest incidence of MG with combined infections were observed in the age
group of 19 – 30 weeks (58.33 per cent) and in the month of December- 8 farms
(22.22 per cent). The season- wise incidence of MG was highest during winter
(Dec, Jan and Feb; 50.00 per cent). The highest mortality was observed in MG
combined infection with E. coli and Pasteurella multocida (11.76 per cent). The
layer chicken affected with MG showed respiratory distress, tracheal rales,
increased lachrymation, nasal discharge, coughing and sneezing. The MG with
combined infections showed reduced feed consumption, loss of body weight,
decrease in egg production, mortality in later stage of diseases, swelling of facial
skin and eyelids, and swollen comb and wattle.
Grossly, MG affected birds showed catarrhal inflammation of trachea and
bronchi, slight pneumonic changes in lungs, cloudiness, airsacculitis and
caseous exudate in thoracic air sacs. Severely affected birds showed congestion
and haemorrhages in lungs, caseous mass in both thoracic and abdominal air
sacs and congested liver with petechial haemorrhages. In MG with E. coli
combined infection, the affected birds showed fibrinous pericarditis and
perihepatitis. Birds affected with MG and P. multocida combined infections
showed multiple miliary necrotic areas in the liver. In MG with A. paragallinarum
combined infection the affected birds showed bilateral infraorbital swelling.
Cytological smears of CRD affected lung showed increased number of
lymphocytes and macrophages.
Histopathologically, focal destruction of superficial cells, goblet cell formation,
hyperplasia of mucosal epithelium, submucosal infiltration of more number of
lymphocytes, macrophages along with haemorrhagic areas were observed in the
trachea of exclusive MG infection. Lungs revealed interstitial haemorrhage,
parabronchiolar oedema, mucosal hyperplasia of secondary bronchiole and
interstitial pneumonia characterised by thickening of interstitium. In the air sacs,
increased thickness due to proliferation of submucosal connective tissue with
fibroblasts, congested blood vessels, destruction of superficial epithelium and
neovascularization in the connective tissue area were observed. The severity of
microscopic lesions was intensified depending upon the number of combinations
of various pathogens. More severe damage to the respiratory organs and
corresponding mortality rate were noticed in MG, E. coli and P. multocida
infections, and MG, E. coli and O. rhinotracheal infections. MG positive antigen
was detected in the cilia of surface epithelium of trachea, parabronchiolar
epithelium of lungs and surface epithelium of air sacs by immunoperoxidase
tests. The positive reaction was seen as brown or red precipitates by DAB and
AEC chromogen respectively.
Description
TNV_THE_Y2015_MVN13022
Keywords
Veterinary Science, Veterinary Pathology