An investigation of enzootic Glasser's disease in a specific-pathogen-free grower-finisher facility using restriction endonuclease analysis.

Enzootic Glassers's disease was investigated to study the epidemiology of the disease strains on a farm where it presented a problem. Restriction endonuclease fingerprinting (REF) analysis technique was used, as all strains of Haemophilus parasuis are biochemically similar and many strains are biochemically untypable. After young weaned pigs were moved from farm A to farm B, Glasser's disease routinely occurred despite the use of antibiotics and a commercial bacterin. Isolates were taken from the nasal passages and from carcasses of clinically affected cases and subjected to REF analysis. Haemophilus parasuis was not isolated from any of the pigs on farm A, but it was isolated from 7/10 and 5/10 nasal swabs taken from farm B. Two H. parasuis strains isolated from clinical cases of Glasser's disease from farm B had an identical REF pattern, but were different from the nasal swabs and the H. parasuis strain contained in the bacterin. The subsequent use of a custom autogenous bacterin made from a clinical isolate of H. parasuis reduced the mortality rate on farm B. This investigation indicates that nasal isolates of H. parasuis are different than those causing clinical disease, and not all bacterin strains are cross protective for other strains.