Isolation of Leptospira interrogans serovar hardjo from a viable premature calf.

A severe outbreak of agalactia in a dairy herd of 80 cows was followed by six premature calvings and an abortion. Serological and bacteriological studies identified Leptospira hardjo as the probable cause. A leptospire isolated from the kidney of a premature calf killed seven weeks post partum was identified as hardjo and it is probable that this infection was acquired in utero. The maintenance of such an infection for a considerable period after birth has not been previously described and may play a role in the transmission of hardjo to susceptible in-contact animals.