Study On The Pathogenesis Of Co-Infection Of Infectious Bronchitis (Ibv) And Escherichia Coli (E. Coli) In Experimental Chickens
Material type: Book ; Literary form:
Publisher: 2015 Dissertation note: 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.
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Pathological Investigation And Molecular Detection Of Avian Pathogenic E.Coli Serogroups In Broiler Birds
Material type: Book ; Literary form:
Publisher: 2016 Dissertation note: The present study was designed to identify the serogroups present in field and to study their pathological effects in experimentally infected broiler chicks. The present study was attempted to scan the rfb gene clusters in APEC predominant serotypes O1, O2 and O78 strains and to develop Multiplex PCR method for serotyping of the O-antigens. The Multiplex PCR method was used for the identification of serotypes of APEC. The second part of the study was to study the pathological lesions caused by most prevalent serogroup in experimentally infected broiler chicks.
A total of 100 tissue samples (lungs and livers) were collected from colibacillosis suspected broiler birds. Streaking was done from these samples on three different media and it was found that 80% isolates were positive on MacConkey media, 60% were positive on EMB media and 40% were found pathogenic for E.coli on Congo red media.
The colonies which were of pink color on congo red media were considered as pathogenic. DNA was extracted from these colonies by boiling method by picking single colony from each petri plate. Extracted DNA was further used for PCR to confirm the three serogroups i.e O1, O2 and O78.
The PCR results showed that 8% isolated samples were found as pathogenic as O2 strain was found dominant among all. Only two genomic DNA samples were found of O1 serogroup After confirmation of serogroups inoculum of Avian pathogenic E.coli O2 strain was prepared to experimentally infect the broiler birds. Birds were infected at the age of day 7 via intratracheal route.
Following the experimental infection of birds, they were monitored for any pathological lesions which were not present significantly while some birds were off feed, reluctant to move, head down posture and were keeping themselves in isolation.
Postmortem of dead birds was performed and pathological lesions were noted. Livers were found to be congested, enlarged and white fibrinous layer over liver was present. Lungs were also affected with the disease and white layer was present on lungs too. Lungs were consolidated and congested.
Histopathology of lungs and livers was performed. It was noted that there was mononuclear cells infiltration and thin fibrinous layer over liver. Thickening of the liver capsule was noted due to infiltration of mononuclear cells and there was marked congestion in hepatic portal areas and the central vein. There was atrophy of adjoining hepatic cords due to greatly distended and congested sinusoids. Besides these changes, hepatocytes in various stages of degeneration along with hemorrhages, areas of congestion and fatty changes in a few places could be seen.
There was infiltration of heterophils, severe congestion, lymphocytes and macrophages in the wall of the bronchus as well as in the peribronchial alveoli. There was marked presence of granuloma in lungs. Some birds displayed thickening of the pleura and consolidated areas covered with yellowish fibrin in lungs.
The experimental infection of avian pathogenic E.coli confirmed the hypothesis that it causes pronounced histopathological lesions in broiler birds.
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