Thesis (Ph.D.) - Cairo University - Faculty of Veterinary Medicine - Department of Microbiology

A total of 200 samples representing intestinal content of apparently healthy and diseased broiler chickens showing enteric disorder symptoms and lesions suspected to be due to necrotic enteritis, were examined by conventional and molecular methods. C.perfringens was isolated with an incidence of 10% (10/100) from apparently healthy chickens, and with an incidence of 25% (25/100) from diseased chickens.Twenty isolates of C.perfringens were proved to be toxigenic with an incidence of 57.1% (20/35), while 42.8% (15/35) were non-toxigenic. Multiplex PCR was performed to toxinotype the 35 C.perfringens isolates, the result showed that all isolates were positive for the alpha toxin gene. Experimental infection with multiple doses of Clostridium perfringens toxoidtype A, C, Net B given S/C in chicken resulted in subclinical necrotic enteritis (NE) diagnosed by decreased body weight gain and. histopathological lesions in intestine and liver. Intestinal samples were collected at 3,7,14 and 37 days after vaccination for enumerating Clostridium perfringens in all groups. Vaccinated groups showed a decreas in Clostridium perfringens count compared with negative and positive groups. Immune response to vaccination by toxoid of type A, type C and type A Net B positive, was estimated. The effect of toxoid administration on intestinal secretory immunoglobuline revealed significant increase in SIgA in all vaccinated groups. Moreover, detection of interleukin 4 also gave a high level in group (2) vaccinated with toxoid A+ NetB while Net B positive type C group (3) showed a steady regulated level. Regarding interleukin 10, regulation has been shown in all immunized groups compared with control {u2013}ve group

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