Antigenic studies on Pasteurella anatipestifer, species incertae sedis, using slide and tube agglutination.

Comparative serological investigations including all available serotypes of Pasteurella anatipestifer, species incertae sedis, have shown that six American serotypes designated by Arabic numbers were covered already by previously described serotypes. Two out of 12 existing English serotypes designated alphabetically were shown to be identical. It is suggested that Arabic numbers are used instead of letters for sero-type designation. Consequently, two new serotypes isolated in Denmark are designated type 12 and 13. Six serotypes including types 1, 2, 3, 8, 9 and 12 were isolated from ducks suffering from P. anatipestifer infection in Denmark during the years 1976-1980. Most outbreaks, however, were caused by types 1 or 3. Occurrence of more than one serotype at the same time was often demonstrated as were changes in serotypes from year to year within a single farm. Because of the occurrence of different serotypes in cases of infection, prophylactic use of autogenous vaccines necessitates continuous surveillance of the serotypes prevalent on the respective farms.