Epidemiology and antibiogram of Riemerella anatipestifer isolated from waterfowl slaughterhouses in Taiwan

Introduction: Laryngeal swab samples collected from three waterfowl slaughterhouses in central Taiwan were cultured and suspected isolates of Riemerella anatipestifer were identified by API 20NE and 16S rDNA PCR. Material and Methods: Serum agglutination was used for serotyping, and antimicrobial susceptibility was tested. Results: Seventy-six R. anatipestifer isolates were detected, and the prevalences in the ducks and geese were 12.3% (46/375) and 8.0% (30/375), respectively. The positive isolation rates were 65.6% for all arriving waterfowl, 76.0% for birds in the holding area, 1.6% for defeathered carcasses, but zero for degummed carcasses. A PCR examination detected R. anatipestifer in the slaughtering area frequently. Serotype B was dominant in both duck (34.8%) and goose (46.7%) isolates, but the wide serotype distribution may very well impede vaccination development. All isolates were resistant to colistin, and 79.7% were resistant to more than three common antibiotics. Conclusion: The results proved that most ducks had encountered antibiotic-resistant R. anatipestifer in rearing, which suggests that the bacterium circulates in asymptomatic waterfowl. It is worth noting that most waterfowl farms were found to harbour R. anatipestifer, and contaminated slaughterhouses are a major risk factor in its spread. Effective prevention and containment measures should be established there to interrupt the transmission chain of R. anatipestifer.