Digital Dermatitis
An emerging condition in feedlot cattle is an unwanted experience.
It's a problem more common to dairy operations, but the beef industry is gaining unwanted experience with digital dermatitis. Iowa State University (ISU) extension veterinarian Jan Shearer calls digital dermatitis an "emerging condition" among feedlot cattle. It can affect breeding stock, too, especially when kept in confinement, but the feedlot is where this malady of many monikers is becoming a significant problem.
Common names include raspberry heel, foot wart and hairy heel wart, but Shearer says digital dermatitis skin lesions really aren't warts. While warts result from viral infections, spirochetes (a type of bacteria) are believed to be the infectious cause of digital dermatitis. However, environmental conditions and animal immune status are thought to be contributing factors.
The lesions often are circular or oval in shape, with raised borders. They may become red and granular in appearance, or may develop papillae. According to Shearer, these hair-like projections actually are outgrowths of skin. Development of lesions is followed by erosion of surrounding skin, presumably due to the secretion of enzymes by the infective organism.
"Eighty to 85% of the time, it's the back feet that are affected," Shearer adds. "Typically, lesions appear on the back side of the foot, between the heels, and can cause tremendous discomfort. It's so painful, as the condition becomes more chronic, that animals try to walk on their toes."
Lesions sometimes develop on the skin between an animal's toes, or on the front of the foot, along the coronary band. Though atypical, Shearer says digital dermatitis sometimes affects the dermis under the hoof horn. Erosion of horn tissue occurs and the infection hinders new horn growth.
Treatments include topical and systemic medications, but a cure for digital dermatitis remains elusive. Veterinarians may prescribe topical application of antibiotics, but some non-antibiotic topical remedies are available commercially. Shearer says copper sulfate is one of the most popular treatments, but results from its use vary.
"Systemic treatments are used, although no data exists to suggest injectable antibiotics are very effective against digital dermatitis," Shearer explains. "It is possible for the lesions to predispose foot rot, however, and that does require systemic treatment."
Lesion location has some bearing on treatment efficacy. Antibiotic sprays are less effective when lesions exist in the cleft between an animal's toes. In such cases, immersing the affected foot in a treatment solution or walking the animal through a footbath may be most effective. Footbaths are often used by dairies for treatment and control of digital dermatitis. Shearer recommends a footbath that's 18 to 24 inches wide and 10 to 12 feet in length — long enough to allow for "two dunks" for each of the animal's feet.
Shearer says footbaths need to be easy to drain, clean and recharge with a treatment agent. A 3% to 5% solution of formalin (contains formaldehyde) and water has been popular and reasonably effective.
"Digital dermatitis vaccines have been developed and marketed, but results have been poor," Shearer states. "I know of no control data showing efficacy."
Evidence does suggest that wet conditions and the presence of manure may predispose an animal to infection. Perhaps the presence of moisture and manure are required for the causative organism to penetrate an animals' skin. Evidence also suggests that immunosuppressed animals may be more susceptible.
"Optimal results usually require a combo approach," Shearer says, "including topical treatment, maybe a footbath, injectable antibiotics in extreme cases and an emphasis on manure management."
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