Prevalence of antibodies to Haemophilus pleuropneumoniae in Iowa swine.

The prevalence of complement-fixing (CF) antibodies to Haemophilus pleuropneumoniae in Iowa swine was determined by testing samples collected randomly from each of 9 crop-reporting areas (9 to 12 counties) in Iowa in approximate proportion to the number of swine marketed annually from each area. For testing, a pooled antigen composed of serotypes 1 to 5 of H pleuropneumoniae was used in a modified direct Microtiter complement-fixation test. Of 7,348 sera tested, 2,362 or 32.1% had CF antibodies (titer greater than or equal to 1:4) to the organism. On a herd basis, 417 of 597 herds or 68.8% had at least 1 animal with CF antibodies (titer greater than or equal to 1:4) to the organism. The clinical problem with H pleuropneumoniae has become significant in recent years, but by no means is the overt disease as prevalent as animals or herds with CF antibodies to the organism.