Experimental infections of mice and guinea pigs with Haemophilus parasuis.

The pathogenicity of Haemophilus parasuis for mice and guinea pigs was examined. Mice were inoculated intraperitoneally with 2 X 10(7) to 2 X 10(9) organisms suspended in saline or in broth containing fresh yeast extract. Most of them survived after inoculation. Death occurred only in mice inoculated with 2 X 10(9) organisms suspended in broth. The recovery rate of H. parasuis from all the dead mice varied from 28.9% of the brains to 71.4% of the lungs. There were no lesions observed in any mouse, except one. Guinea pigs were inoculated intraperitoneally with 1 X 10(8) to 1.6 X 10(10) organisms suspended in saline. Many of them died after showing septicemia and serofibrinous serositis, which were associated with purulent leptomeningitis or meningoencephalitis in some of them. H. parasuis was recovered abundantly from many organs, including the brain, in the guinea pigs. It was also recovered from guinea pigs inoculated with 1.8 X 10(9) organisms by various routes. Serositis was observed in guinea pigs inoculated intramuscularly or intrapulmonarily. These results suggested that guinea pigs might be available for investigation of the pathogenicity of H. parasuis.