Virulence of raptor-origin Pasteurella multocida in domestic chickens

Pasteurella multocida belonging to somatic serotype 1 and capsular type A h as been known to cause avian cholera in domestic poultry. Pasteurella multo cida serotype 1 has also been isolated from raptorial birds. However, pe ca psular type for these raptorial isolates remains unknown. Moreover, the vir ulence of these raptorial isolates for domestic poultry has not been determ ined. The objectives of this study were to determine the capsular type of r aptorial P. multocida serotype 1 isolates and to determine if these isolate s were virulent for domestic chickens. Study chickens were inoculated with one of three P. multocida isolates. Isolate WESO-1 was obtained from a west ern screech owl (Otus kennicottii) and isolates RTHA-2 and RTHA-4 were isol ated from two red-tailed hawks (Buteo jamaicensis). These isolates were giv en by either the oral, intravenous, or intraocular route. Control birds wer e given brain-heart infusion broth. The capsular serotypes of three isolate s were also determined. The RTHA-2 and RTHA-4 isolates belonged to P. multo cida capsular type A. The WESO-1 isolate belonged to capsular type F. Resul ts also demonstrated that, for the isolates examined, the intraocular route did not cause mortality in chickens. There was mortality in all groups for the intravenous route. However, Various mortality patterns were observed w hen P. multocida was given orally for the three different isolates. The RTH A-4 isolate (serotype 1:A) was the most virulent for domestic chickens. The WESO-1 isolate (serotype 1:F) was the least virulent for chickens among th e raptorial isolates examined.