Surveillance for Pasteurella multocida in Ring-Necked Pheasants (Phasianus colchicus) After an Outbreak of Avian Cholera and Apparently Successful Antibiotic Treatment.

Avian cholera is a significant disease of domestic and wild birds caused by the bacterium Pasteurella multocida (PM). In poultry, a major source of PM infection is chronic carriers, domestic birds that have become infected and recovered or had subclinical infections. Although outbreaks of avian cholera in ring-necked pheasants (Phasianus colchicus) have been reported, the potential for chronic carriers is unknown. To address this, we conducted surveillance for PM in a flock of captive ring-necked pheasants after an outbreak of avian cholera that responded positively to antibiotic treatment based on resolution of morbidity and mortality. At approximately 1 mo after antibiotic treatment, oropharyngeal swabs were collected from 300 pheasants (out of a total population of ~2300) in a single winter holding pen. All samples were tested for PM through routine aerobic bacterial culture, but none of the samples were positive. In addition, there were no additional outbreaks within this infected pen over the subsequent months. These data provide preliminary evidence to suggest that pheasants that respond to antibiotic therapy may be less likely to become chronic carriers of PM than other poultry species, such as chickens (Gallus domesticus). However, due to marked phenotypic and biologic differences between PM strains, additional studies are needed to further support or refute these findings and better understand avian cholera in this species.