Vet Column 9-20-10
September 20, 2010
Digital dermatitis, more commonly known as footwarts, is a worldwide, contagious, painful dermatitis affecting the feet of cattle, most often seen on dairy operations. It is painful enough that it can result in clinical lameness, reduced milk production, and decreased reproductive efficiency. Although progress has been made on the exact cause, and data is available to support the role of a species of bacteria involved in the development of the disease, the exact cause remains unknown.
Common treatments include chemical disinfectants and extralabel use of antimicrobials applied under a bandage as a paste, as a topical spray, or as footbath additives. In the United States, no antimicrobials are currently approved for treatment of footwarts. About 50 percent of the time, recurrence after antimicrobial treatment occurs by 49 to 100 days after treatment according to one published study involving dairies in California.
When applied topically as a spray or under a light bandage, lincomycin hydrochloride and oxytetracyline hydrochloride are reportedly effective. To better understand some of the clinical impressions associated with treating this disease, investigators from the University of California-Davis recently published data comparing these two antibiotics for the treatment of footwarts. They also examined whether gross visual assessment of treated and untreated lesions agreed with results of microscopic examination, and whether the surface digital skin flora from affected and healthy cattle was different.
This study involved 25 cows with footwart lesions identified within a 1,200-cow Holstein, commercial, free stall-housed dairy herd with an approximately 45 percent prevalence of footwarts. An affected cow could possess single or multiple lesions. Footbaths and individual cow treatments were not used on this dairy during the study. Cows with footwarts were identified by examining the hind feet after cleaning with a water hose. Pain was determined by assessing the response to the spraying of water on the lesions.
Cows were restrained on a hydraulic chute for examination, scoring and treatment. Three cows served as controls with 11 cows treated with 10 grams of lincomycin hydrochloride soluble powder and 11 cows treated with 10 grams oxytetracycline hydrochloride soluble powder. Each treatment was created by adding three to four milliliters of deionized water to the powder, paste created and applied to gauze, which was then applied to the lesion and held in place by a bandage. All bandages were removed four days after bandaging.
Biopsies were taken on day one and day 30 for examination of the skin and cultures. All animals were examined on the hydraulic chute on day 12 or 14 to monitor progress.
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Results of this study indicate there was no difference in clinical response to lincomycin or oxytetracycline as a paste bandage, removed at four days. Visual inspection 30 days after initiating treatment, 8 of 11 lincomycin treated and 7 of 11 oxytetracycline treated lesions appeared healed. Visual assessment, however, only matched the biopsy assessment about 50 percent of the time, leaving only about a third of the initial cases responding to the one treatment of lincomycin or oxytetracycline with a four-day bandage.
This study emphasizes the need for continued diligence involving early detection, treatment, and monitoring when footwarts are diagnosed in cattle herds.