Differential Diagnosis of Lameness in Sheep

Introduction.

Lameness in sheep is a major welfare and economic concern in most sheep-keeping countries. In adult sheep the most common site of lameness is in the foot and it is these conditions which will be addressed in this paper. It is important to note, however, that important systemic diseases such as foot-and-mouth disease and blue tongue also cause lameness. In younger animals, joint infections such as neonatal polyarthritis (often associated with Streptococcus dysgalactiae infection) and polyarthritis caused by Erysipelothrix rhusiopathiae can affect significant numbers of animals. The latter organism also causes post-dipping lameness. Very old animals may suffer from osteo-arthritis, particularly affecting the elbow joints. The most common types of foot lameness in the UK on a flock basis are interdigital dermatitis (often referred to as ‘scald’), footrot and the relatively newly-recognised condition contagious ovine digital dermatitis (CODD), so far only reported in UK. Although each of these conditions has been linked with particular infectious agents, it appears that the etiology of each may, at least in UK, be microbiologically somewhat more complicated (Moore and others, 2005). White line lesions are common, although cause lameness in only a minority of cases. Other common causes include soil balling, interdigital hyperplasia, toe granuloma, laminitis and sepsis of the pedal joint (Winter, 2004a). ....