Ringworm in lactating sows

A 100-sow farrow-to-feeder farm with an outdoor gestation lot had a 4-year history of ring-like skin lesions in lactating sows. On average, 90% of sows in each 5-week batch developed lesions within a week of entering the farrowing house. Lesions beginning as 2to 3-cm circles of dark, crusty skin coalesced into larger areas on the back, sides, and ventral abdomen. No etiologic agent was identified in hair shafts and skin biopsies in initial samples. A second sampling revealed diffuse fungal elements in exfoliated epidermis. The tentative diagnosis was ringworm. Control strategies were limited by cost and labor constraints defined by the producer. Goals agreed upon included reducing the number of organisms in the farrowing house and the number that entered the farrowing house on the sows, and limiting recontamination of the environment by aggressively treating lesions. Sows were thoroughly washed before entering the farrowing house. Washing and disinfecting protocols used in the farrowing house and topical treatment of lesions were improved. Prevalence of lesions in the next farrowing group was 30%, and in subsequent groups remained < 10%. The average number of lesions per sow decreased from > 20 to < 5, and lesions were much smaller.