Diagnosis of dermatophilosis in dairy cattle in Kerala, India

Skin scabs and scrapings from 82 dermatitis cases in dairy cattle were subjected to detailed bacteriological, mycological, parasitological and molecular studies. Microscopical examination of Giemsa or Gram’s stained smears of scab material from the lesions revealed characteristic gram positive septate branching filaments with typical tram track appearance suggestive of Dermatophilus congolensis in 72 samples (91.5%). Culture of scab materials in sheep blood agar under anaerobic condition yielded typical beta haemolytic colonies of D. congolensis in 75 samples, which were further confirmed by colony morphology, staining characters and biochemical reactions. Molecular confirmation of the isolates was carried out using polymerase chain reaction with primers based on 16S rRNA which yielded specific band of 500bp. The pathogenicity of the isolates was also proved by experimental inoculation into rabbits.