Establishment, validation and use of the Kielstein-Rapp-Gabrielson serotyping scheme for Haemophilus parasuis

Objectives: To produce antisera to the 15 recognised reference strains of the Kielstein-Rapp Gabrielson (KRG) serotyping scheme for Haemophilus parasuis, validate those sera and use them to serotype 46 Australian field isolates of H parasuis. Design Antisera were produced in rabbits and validated by cross-testing with the reference strains and re-testing 15 Australian field isolates of H parasuis that had been previously serotyped in the United States of America. The validated antisera were then used to determine the serovar of 46 Australian isolates. Results: Monospecific antisera were produced for 14 of the 15 KRG serovars of H parasuis. Two Australian field isolates, confirmed previously as serovars 1 and 7, were used to produce monospecific antisera for serovars 1 and 7 respectively. The antiserum for serovar 4 gave a one-way cross reaction with the antigen of serovar 14. The typing antisera correctly typed all 15 H parasuis that had been previously typed by antisera produced overseas. The 46 field isolates were shown to belong to serovars 2 (two isolates), 4 (one isolate), 5 (18 isolates), 12 (two isolates) and 13 (four isolates). The remaining 19 isolates were non-typable. Conclusion: Serotyping of H parasuis isolates is now available in Australia. Hparasuis serovars 5 and 13 remain the predominant serovars present in Australian pigs