POST-SHEARING MANAGEMENT AFFECTS THE SEROINCIDENCE OF CORYNEBACTERIUM-PSEUDOTUBERCULOSIS INFECTION IN SHEEP FLOCKS

Associations between the incidence of caseous lymphadenitis (CLA) in s heep and post-shearing management and environmental factors were exami ned in a prospective study. CLA incidence was measured in 126 groups o f 1- and 2-year-old sheep in 70 Western Australian Becks selected from the prevalence of cull-for-age ewes with CLA lesions at abattoirs. CL A incidence was assessed using a CLA toxin ELISA. Dichotomous and poly chotomous stepwise logistic regression methods were compared in examin ing the effects of management and environment on CLA incidence. Shower dipping sheep for ectoparasite control after shearing increased the o dds of high CLA incidence by five to six times and keeping sheep under cover for 1 h or more after shearing increased the odds of being in h igh CLA incidence categories three-fold. The seroprevalence of existin g CLA infection within each age group affected incidence more than did the overall slaughter-based flock estimate. This suggests that CLA sp reads mostly within groups of sheep shorn together.