CHARACTERIZATION OF ISOLATES OF HAEMOPHILUS-PARAGALLINARUM FROM ARGENTINA

The biochemical and serological properties of Haemophilus paragallinar um isolates recovered from 11 recent outbreaks of infectious coryza in layer hens and one case of swollen-head syndrome in broilers in Argen tina are described. Twenty-four isolates had the typical biochemical p roperties of H. paragallinarum. All isolates were serotyped according to the Page scheme. Ten of the isolates were serovar A, 11 were serova r B, one was serovar C, and two isolates could not be serotyped. The i solates were also examined using a panel of monoclonal antibodies (MAb s) for Page serovars A (one MAb available) and C (three MAbs available ). The serovar B isolates all failed to react with any MAb. The serova r C isolate reacted with all three serovar C MAbs but not with the ser ovar A MAb. Only six of the 10 serovar A isolates reacted with the ser ovar A MAb. These results indicate that H. paragallinarum isolates fro m Argentina are antigenically distinct from those examined in other co untries, and it is suggested that coryza vaccines intended for use in Argentina may be more effective if based on local strains.