ABSTRACT
Sporadic outbreaks of fowl cholera have been experienced from time to time in Jos, Nigeria despite vaccination against the disease. This study was conducted from November, 2010 to October, 2011 to determine the phenotypic and genotypic profile of Pasteurella multocida isolated from chickens in Jos, Nigeria. A total of 400 oro-pharyngeal swabs from apparently healthy chickens and 2,000 samples consisting of bone marrow, heart, liver, lungs and spleen (400 each) were collected from 400 clinically sick chickens and analyzed bacteriologically for Pasteurella multocida. Swab from each sample was cultured on 7% defibrinated sheep blood, MacConkey and casein sucrose yeast agar. Presumptive colonies of Pasteurella multocida were subjected to biochemical tests. Isolates identified by biochemical tests were further subjected to Microbat 24E test and Pasteurella multocida specific Polymerase Chain Reaction. Multiplex PCR typing using specific primers for capsular types CAP A, CAP B, CAP D, CAP E and CAP F was carried out on all Pasteurella multocida isolates. Biochemical tests identified Pasteurella multocida in 1.0% of clinically sick chickens. The monthly frequency of isolation of P. multocida showed that the bacterium was isolated mostly between the months of July and October. Pasteurella multocida was isolated from 5(1.3%) apparently healthy birds. Pasteurella multocida serotypes A: 1, A: 3 and A: 4 were identified in Jos, Nigeria. Polymerase Chain Reaction recognized only 12 P. multocida isolates out of 25 isolates, showing a specific amplicon of 460 base pairs. The amplification of capsular genes in these 12 isolates by multiplex PCR showed band sizes of 1,044 base pairs signifying that all the 12 P. multocida isolates belong to capsular group A. Disk diffusion test was employed to assess the sensitivity of all P. multocida isolates confirmed by PCR. Ciprofloxacin and gentamicin were highly effective (100%) against the twelve P. vii multocida isolates. High rates resistance by P. multocida isolates were recorded for ampicillin and amoxicillin/clavulanate acid among others. The gross lesions in chickens infected with P. multocida serotypes A1 and A3 were prominent keel, congested heart, liver, kidneys and lungs. Histopathologically, moderate to severe lymphocytic, heterophilic and macrophage cellular infiltration were noticed in the lungs and heart of chickens. In Japanese quails, congested heart, liver and lungs were seen. Cellular infiltrations were noticed in the lungs and heart of infected Japanese quails. Pathogenicity study indicated that P. multocida serotypes A: 1, A: 3 and A: 4 caused (100%) mortality in mice. Moderate cellular infiltrations were noticed in the lungs and heart of mice. In conclusion, it was observed that P. multocida serotypes A: 1, A: 3 and A: 4 were identified in Jos metropolis and they caused mortality in experimentally infected chickens, Japanese quails and mice. This indicates that the antigenic component of the fowl cholera vaccine which is capsular group A and serotype 1 that is produced in the country may be limited in scope; it is therefore recommended that the vaccine should be re-validated by incorporating the prevailing serotypes of P. multocida in Nigeria such as serotypes A: 3 and A: 4 in order to widen the protection margin.
