Stillbirth/perinatal weak calf syndrome: a study of calves infected with Leptospira.

Leptospiral infection has been reported in calves which were either stillborn or dead from perinatal weak calf syndrome; 356 such calves were examined for evidence of associations between leptospiral infection and macroscopic, histological and microbiological findings, and the parity of the dam. Calves in which leptospiral antigen was detected in the placenta were significantly lighter by an average of 6 to 10 kg than calves with no antigen in the placenta. Calves infected with Leptospira were more likely to be infected by Actinomyces pyogenes or Bacillus species. No other significant associations were detected. The adrenal gland, lung and placenta were the most useful organs to examine for leptospiral antigen. The placenta was the only antigen-positive tissue 8.9 per cent of the calves submitted with their placenta.