الفهرس Only 14 pages are availabe for public view
 |  | from | 226 |  |  |
| | | from | 226 | | |
Abstract
A surveillance study for diagnosis of C. perfringens enteritis affecting early weaned rabbits was carried out on sixteen rabbit flocks, during the period 2012 - 2014. Two hundred and sixty seven rectal swabs from diseased rabbits suspected to be infected with C. perfringens, moreover tissue samples from intestine and liver of 48 freshly dead rabbits were aseptically collected for isolation, biochemical and molecular identification of C. perfringens. Tissue specimens from small, large intestine, liver, spleen and kidney from each examined freshly dead rabbits were processed for histopathological examination. The examined breeds were (Baladi, French, California, Bauscat, Chinchilla, New-Zealand and Dutch) with age ranged from 3-9 weeks and mortality rate 12-60%. Observed clinical signs were severe diarrhea and bloat. Postmortem lesions showed different degrees of enteritis, liver and kidney congestion with enlargement. Histopathological alterations were necrohemorrhagic enteritis in small and large intestine, portal congestion, periportal edema, sinusoidal dilatation and hepatic hemorrhage in liver, depletion and necrosis of lymphoid elements in spleen and degeneration in the tubular epithelium, vacuolization of epithelial lining of renal pelvic with perivascular edema in kidney. The recovered pathogenic C. perfringens were (118/267) 44 % from rectal swabs, (40/48) 83% from the intestine and (9/48) 18% from the liver. C. perfringens enteric infection could be detected in a higher rate in both autumn & winter seasons especially at 3-4 weeks of age. Most affected breeds were Baladi, followed by French, California, Bauscat, Chinchilla, New-Zealand and Dutch breeds with a percentage of 83, 80, 75, 70, 50, 35 and 20%, respectively. The C. perfringens isolation was high in rearing of mixed breeds than single breeds. The females showed recovery rate (99/105) 94% which more than males (68/210) 32%. Rabbits which reared on ground were more infected with C. perfringens than those reared on battery system. The isolation rate of C. perfringens in rabbit flocks used antibacterial drugs was 11 flocks out of 16 (68%). All isolated C. perfringens strains were toxinogenic to Swiss mice. The result of multiplex PCR revealed, 90 out of 167 (53.8%) C. perfringens strains were type A, 9 out of 167 (5.3%) were type B, 58 out of 167 (34.7%) were type C, 5 out of 167 (2.9%) were type D and 5 out of 167 (2.9%) were type E. Alpha gene of C. perfringens type A, B, C, D and E was sequenced and submitted on gene bank with accession numbers KJ740693, KJ740694, KJ740695, KJ740696 and KJ740697, respectively. Beta gene of C. perfringens type B and C was sequenced and submitted on gene bank with accession numbers KP742965 and KP768395, respectively. Epsilon toxin of C. perfringens type B and D was sequenced and submitted on gene bank with accession numbers KP751213 and KP751212, respectively. Iota toxin of C. perfringens type E was sequenced and submitted on gene bank with accession number KP751211. The genetic diversity of the submitted toxin genes were compared with sequences deposited in the NCBI database to infer phylogenetic relationships between them. The clinico-pathological differentiation between different types of C. perfringens was adopted in experimentally infected weaned rabbits. The results of post-mortem lesions (PM), histopathological pictures and lesion scoring in different experimental groups, revealed the probability of usage them as a differentiating tools for diagnosis of different types of C. perfringens infections in weaned rabbits. Six monovalent inactivated C. perfringens type A vaccines against rabbit enterotoxaemia were prepared, evaluated and compared with commercial vaccine. For the first time in Egypt and all over the world, four bivalent inactivated vaccines of C. perfringens type A&C and four polyvalent inactivated vaccines of C. perfringens type A, B, C and D were prepared using whole culture bacterin or toxoid with different adjuvants (Montanide ISA 206 and Alum. hydroxide gel). The prepared vaccines were used for dam vaccination. The results revealed that, toxoid prepared vaccines were more effective than whole culture bacterin. Montanide oil ISA 206 provoked efficient, protective and prolonged immunity. Maternal immunity affords good degree of protection for newly weaned rabbits as expressed by SNT, ELISA and challenge test results. The locally prepared inactivated monovalent C. perfringens vaccines were protective only for homologous strains. Bivalent vaccines were protective against homologous strains but partially protective against heterologous strains. Polyvalent vaccines were protective for newly weaned rabbits against infection with C. perfringens different types.