Postdipping Lameness in Sheep

With time and repeated use, dipping solutions, which have little or no bacteriostatic activity, become heavily contaminated with various species of bacteria. E rhusiopathiae is a common contaminant, and its presence in the dipping vat, sometimes in enormous numbers, leads to infection of skin wounds during dipping. Small skin abrasions in the region of the hoof and fetlock joint are a common portal of entry. Lesions extending from these wounds to the laminae of the hoof cause acute postdipping lameness. Outbreaks may also occur when sheep must walk through wet and muddy areas that are heavily contaminated with the organism.

Two to 4 days after dipping, a variable number (up to 90%, but usually ~25%) of sheep in the flock may be lame in one or more limbs. Affected limbs appear normal except for the hoof and pastern regions, where the coronary band may be swollen, hot, and painful. Most sheep recover spontaneously in 2–4 wk with nothing more serious than a slight loss of body weight. In some outbreaks, however, administration of penicillin for 5 days may be necessary to salvage affected sheep. Septicemia and polyarthritis are not common with this condition.

Discarding heavily contaminated dips is the best way to prevent infection with E rhusiopathiae and the lameness associated with this condition. Using an appropriate bacteriostat in dip solutions may reduce the incidence of the condition.