Development of a New Serological Test for SerotypingHaemophilus parasuisIsolates and Determination of Their Prevalence in North America

ABSTRACT Haemophilus parasuis causes polyserositis in swine. Fifteen serovars have been characterized by immunodiffusion test, but many field strains are not typeable. Isolates ( n = 300) of H. parasuis from animals in North America were serotyped by a new indirect hemagglutination test. The test was rapid and effective for serotyping of H. parasuis , and serovars 4, 5, 13, and 7 were the most prevalent serotypes.