Digital dermatitis: report of an outbreak.

An outbreak of digital dermatitis in a dairy herd in the Gauteng province of South Africa is described in which 72% of the lactating herd was affected. Many of the affected cows showed a severe lameness and a drop in milk production. Other complications included heel horn erosion, under-running of heel horn and boxy claws. The diagnosis was made on the typical clinical appearance of the condition and the presence of spirochaetes on histopathological sections from biopsy material. The condition responded to spraying affected feet with an oxytetracycline mixture after cleaning with water using a high pressure hose. The prevalence was reduced to 28% after one month of therapy. A repeat outbreak occurred on the same farm 7 months later during which time 37% of the lactating herd was affected. Of the cows affected, 48% represented new cases, whereas the rest were reinfections.