Avian cholera: Prevalence, virulence, pathogenesis and role of vitamin A in disease induction.

摘要

Pasteurella multocida, the causative agent of avian cholera, has been recognized as one of the important infectious agents for avian species. Despite vaccination efforts, avian cholera outbreaks still occur in the commercial poultry. However, the manner in which birds become infected remains unknown. Oropharyngeal carriages of P. multocida have been reported in both domestic poultry and free-living birds. Buteo hawks carried P. multocida in their submucosal glands of the esophagus and pharynx, and lesions were found in their oropharynx. These glands also had squamous metaplasia, which is similar to the lesion caused by vitamin A deficiency. Via squamous metaplasia P. multocida could gain access to the host tissues since P. multocida enters the host through the mucus membrane. Thus, the objectives of this study were to determine the virulence of Buteo hawks' P. multocida isolates in the poultry and the role of damage mucus membrane in the pathogenesis of Pasteurella multocida.;Buteo hawks' and Otis owl's P. multocida isolates were inoculated in broiler chickens. The Buteo hawk isolates were more virulent than the Otus isolate. Route of inoculation also contributed the differences in virulence of these isolates. The oropharyngeal carriage was also studied in turkeys. Normal meat turkeys do not carry P. multocida whereas turkeys from the outbreak farms carry P. multocida. Similarity in the trends of antibiotic susceptibility were common among capsular serotype A isolates whereas variation of antibiotic susceptibility trends were found among the untypeable isolates. Pasteurelia multocida was inoculated when the mucus membrane was damaged due to vitamin A deficiency in the turkeys. Higher mortality and the faster invasion of P. multocida was faster were found in the vitamin A deficient turkeys.;These studies provide evidence that P. multocida carried by the raptorial birds are virulent for the domestic poultry. In addition, healthy turkeys do not carry the P. multocida whereas the convalescent turkeys carry the P. multocida in their oropharynx. If there was epithelial damage in the oropharynx, P. multocida could gain an access to the host and this damaged epithelium accelerate the invasion and virulence of P. multocida in turkeys.