Sohail Khan (2013-VA-606)

Study On The Pathogenesis Of Co-Infection Of Infectious Bronchitis (Ibv) And Escherichia Coli (E. Coli) In Experimental Chickens - 2015 - 64p.;

Infectious bronchitis and colibacillosis are infectious diseases affecting chicken of all ages and breeds. They are of major economic importance in commercial chicken flocks, causing huge losses. As both in humans and animals it is well documented that preceding respiratory infection of virus predispose individual to bacterial infection. Moreover, mix infection in poultry which occur when different organisms simultaneously invade birds is a major threat to poultry industry causes highly epidemic debilitating disease with high mortality which eventually leads to economic catastrophe. In recent past prevalence studies of field, E. coli had been reported with high prevalence and exaggerated disease along with other respiratory pathogens, additionally IBV had also isolated from same flocks in same season. Although a plethora of pioneering work had been done on IBV and E. coli in the previous decades but still a window in time exist in revealing there co-infection. Looking to field scenario in our country, the present study was designed to study an ideal challenge model for IBV and E. coli, by reproducing the natural infection.
80 SPF day old broiler birds were arranged into four groups, (A, B, C and D). Each group was comprised of 20 birds. Group D served as uninoculated control while, Group A and B were challenged with IBV on 23rd day of trails, and Group B and C were inoculated with E. coli infection on day 26th. Birds, (n=3) from each group were slaughtered on various days post infection, gross and histopathological lesions were observed and serum samples for HI were taken, throughout experiment. Variable clinical signs were recorded in various groups. In IBV infected group, respiratory distress i.e., tracheal rales, coughing, sneezing and gasping were noted during early stages, later up to 10 days post infection watery diarrhea with ruffled feathers were observed. In mix infected group clinical signs manifested rapidly and were persistent with high severity. Gross lesions in mixed infection were more profound,
including; airsacullitis, tracheitis with catarrhal exudation throughout respiratory tract; severe sepicemic lesions i.e. perihepaitis, pericarditis, pneumonia and polyserositis with swollen and pale kidneys distended by urates. 5 birds died in mix infected group revealed ascites with asphyxiation of trachea with caseous exudate. While in IBV infected group lesions were mild and confined to trachea, airsac and kidneys. Mortality was high in mix infected followed by IBV in which two birds died. While in E. coli and control group mortality were not noted. Histopathological lesions in mix infected group were aggravated markedly tracheal epithelium degeneration, deciliation and sloughing; congestion, interstitial nephritis, leukocytes infiltration, tubular degeneration and necrosis while were observed. In lungs, pneumonia of peribronchiolar area and interstitium with lymphocyte and macrophages infiltration, additionally degeneration and vacuolization of hepatocytes with focal necrotic areas were also noted. In IBV and E. coli group microscopic lesions were of mild degree. GMT of both IBV and mix infected birds were high but were not significant different (P>0.05). Among the groups, statistically significant increase in FCR of birds in mix infected group was observed followed by E. coli, with IBV infected came third in the row. On the bases of these findings we might conclude that mix infection of IBV and E. coli causes severe lesions with high morbidity and mortality.

Department of Pathology


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