Long-term observations on the dynamics of bovine digital dermatitis lesions on a California dairy after topical treatment with lincomycin HCl.

The objective of this study was to observe the dynamics of clinical cure and recurrence of the lesions of bovine digital dermatitis for 11 months after treatment with topical lincomycin HCl. The study was a clinical follow-up of 39 active bovine digital dermatitis lesions (from 29 cows). Cows with active, painful bovine digital dermatitis (BDD) lesions on the interdigital commissure of the rear feet were identified on day 0. On day 1, lesions in all cows were photographed and full-skin thickness 6mm punch biopsies were obtained for histological evaluation. All lesions on all cows were treated with topical lincomycin paste under a light bandage. On days 12 and 23, a subsample of 10 lesions was randomly selected, photographed, and biopsied. On day 37, all lesions on all cows were photographed and biopsied. After day 37, lesions were evaluated on a monthly basis. All lesions were photographed at each observation until day 341 (end of study) but only cows that had macroscopically active lesions were biopsied. Of the 39 lesions treated on day 1, 21 (54%) required re-treatment on at least one occasion before day 341. Macroscopic classification agreed well with histological classification when lesions were small, focal and active (M1 lesions) or large, ulcerative and active (M2), but agreement was variable for lesions that had healed macroscopically (M5) or that were chronic (M4). A transition model showed that M1 and M2 lesions were 27 times more likely to be an M2 lesion on the next observation than to be a healed (M5) lesion.