Murine infection model for contagious equine metritis: a new venereal disease of horses.

An infection model in laboratory mice for studying the bacterium (proposed name Haemophilus equigenitalis) causing contagious equine metritis is described. Small porous chambers were implanted subcutaneously into mice and after 1 to 3 weeks were inoculated with H equigenitalis. Infections that persisted for > 30 days were established by direct transfer of infective chamber fluid or by injection of laboratory-grown cultures. Immunization of mice with formaldehyde-treated cells induced significant, strain-related immunity to infection and did not appear to require complement as a protection mediator. Substantial differences in staining characteristics and cell morphology were observed between bacteria grown in mouse chambers and those grown on a laboratory medium. These differences were more apparent in smears of the organism stained by a modified Gimenez method than in smears stained by the conventional Gram stain. This murine model may be a convenient and inexpensive method for studying the immunobiology of this newly discovered animal pathogen.