Bovine leptospirosis: experimental infection of pregnant heifers with a strain belonging to the Hebdomadis serogroup.

Twenty pregnant heifers were inoculated with a leptospire of the Hebdomadis serogroup. Leptospiraemia was accompanied by pyrexia which lasted from one to five days. Sixteen animals had relapses of fever. One of these aborted and two produced weak calves, one of which was premature. In the heifers, leptospires localised in the placentae, where they were demonstrable for 14-60 days after inoculation, and in the renal tubules for as long as 174 days. They were also demonstrated in liver, kidney and lung from the aborted fetus. Antibodies were detected in susceptible heifers six days after inoculation and maximum titres of up to 1:100,000 developed between 11 and 21 days. A titre of 1:10 was demonstrated in the serum of a premature live calf. These findings indicated that leptospires of the Hebdomadis group were capable of causing abortion in cattle.