ASSOCIATION BETWEEN CESSATION OF LEPTOSPIRURIA IN CATTLE AND URINARY ANTIBODY-LEVELS

The shedding of Leptospira interrogans serovar hardjo in the urine of cattle and the local and systemic response to these organisms was moni tored in experimentally and naturally infected animals. Twenty yearlin g heifers, 10 infected by the instillation of leptospires into the con junctival sac (supraconjunctival route) and 10 infected intrauterinely , shed leptospires for up to 60 weeks after infection. Five of 15 natu rally infected pregnant heifers with microscopic agglutination test ti tres greater-than-or-equal-to 1:300 continued to shed leptospires from 28 to 40 weeks after initial detection. Serovar hardjo was isolated i nfrequently from the urine of a further five naturally infected animal s during the first eight weeks of the study but no leptospires were is olated from the remaining five animals for the duration of the study p eriod (84 weeks). Cessation of leptospiruria in the 20 experimentally infected animals and in the five naturally infected persistent excreto rs was invariably associated with a sharp increase in urinary anti-lep tospiral IgG and IgA antibody levels.