Possible role of leptospires of the Pomona serogroup in sporadic bovine abortion in the south west of England

An investigation of a small outbreak of abortion in mixed-age cows in a dairy herd in Somerset produced circumstantial evidence that a leptospire belonging to the Pomona serogroup was the causative agent. Although the initial epidemic involved more than 30 per cent of the herd, agglutination titres did not persist in the majority of animals and bacteriological monitoring produced no evidence that this leptospire could establish endemic infection in dairy cattle. An isolate recovered from the kidney of a cow which aborted was found to be similar to mozdok, a serovar maintained by free-living species in continental Europe, and it is probable that free-living species also maintain the Pomona serogroup organisms that have been isolated in England. Clinical disease caused by infection of domestic stock with Pomona serogroup organisms other than pomona has not been recognised in other countries but this may be because of the presence of endemic infection with pomona, a serovar that causes a very similar clinical and serological response.