In-ovo and in-vivo pathogenicity study of avain Escherichia coli isolated from cases of colibacillosis in chickens

Twenty-one isolates of Escherichia coli were recovered from clinical cases of colibacillosis in chickens of different field outbreaks. These isolates were serotyped and the pathogenicity was determined in 11-day-old embryonated chicken eggs, one-day-old and 4-week-old chicks. Of the 21 isolates, 17 were found pathogenic, whereas 4 isolates were found non-pathogenic. The predominant pathological lesions observed were perihepatitis, pericarditis and airsaculitis in one day old and 4 week old chicks. In embryos the lesions included thickening of chorio-allantoic membrane and hemorrhages in the head and appendages.