Epidemiological and bacteriological studies of Corynebacterium equi isolates from Californian farms

Soil samples were collected from 6 horse breeding establishments in California and cultured for Corynebacterium equi. Only 3 of the farms had a history of the occurrence of pneumonia caused by C. equi. One farm had experienced an outbreak in 5 out of 6 foals just before soil sampling. Soil isolates were identified as C. equi on the basis of physical and biochemical characteristics found to be consistent with isolates of equine origin. C. equi was found in many soil samples within endemic areas where greatest concentrations were obtained in places accessible to horses. On non-endemic farms, only areas frequently inhabited by affected foals contained the organism. Pharyngeal, vaginal and faecal cultures from the dams of 4 affected foals were negative for C. equi.