Immunisation of mares to control endometritis caused by Streptococcus zooepidemicus

Normal mares were immunised by the intramuscular and intrauterine administration of an antigen with adjuvant and they and unimmunised control mares were later challenged by the intrauterine instillation of pathogenic Streptococcus zooepidemicus; the response of all the mares was monitored clinically and bacteriologically for seven days. Significantly fewer S zooepidemicus were present in cervical swabs taken from the immunised mares than from the control mares (P < 0.01) and the degree of inflammation in the genital tract of the immunised mares was also significantly less (P < 0.001). This protective effect of immunisation was associated with the specific IgG response in the serum, and an IgG and IgA response in the uterine secretions. These results are the first demonstration that a previous immunisation with a suitable antigen can reduce an infection of the reproductive tract of mares.