PRESENCE OF ANTIGEN AND ANTIBODIES IN SERUM AND GENITAL DISCHARGES OFHEIFERS AFTER EXPERIMENTAL INTRAUTERINE INOCULATION WITH LEPTOSPIRA-INTERROGANS SEROVAR HARDJO

The excretion of Leptospira interrogans serovar hardjo in cervico-vagi nal mucus (CVM) or urine and the local and systemic immune responses t o the organism were monitored in eight susceptible heifers after intra uterine inoculation while six similar heifers served as controls. All the heifers were inseminated at the subsequent oestrous periods. The o verall percentage pregnancy rate (the number of pregnancies divided by the total number of inseminations) was lower in the infected heifers than in the controls though not significantly (33.3 v 50.0 per cent). Leptospires were detected, in either the urine or the CVM of six of th e eight infected heifers during the study period of 15 weeks, either b y direct immunofluorescence or dark ground microscopy; the bacteria di d not grow in culture from any of the CVM samples. The control heifers remained free from evidence of infection. In the infected heifers, me an titres of at least 1:100 in a microscopic agglutination test were m aintained for one to two weeks before declining to 1:10 to 1:30, where as in serum IgG-ELISA tests (developed by using either protein or carb ohydrate antigens), antibody titres of at least 1:100 were maintained throughout the study. During oestrous periods. IgA antibodies were det ected more frequently in CVM with titres which were usually higher tha n the titres of IgG.