Association between management practices and within-herd prevalence of Cryptosporidium parvum shedding on dairy farms in southern Ontario

To identify management practices associated with an increased within-herd prevalence of Cryptosporidium parvum shedding on dairy farms in southern Ontario, fecal samples were taken from 1089 calves aged 7–28 days, from 119 herds. Information on management practices was obtained by administering a questionnaire compiled using a modified Delphi technique. Data were analyzed using univariable and multivariable negative binomial regression. Overall, 30% of the calves in the study were shedding C. parvum oocysts, with at least one positive calf detected in 77% of herds. Within-herd prevalence ranged from 0 to 80%. Predictors significantly associated with an increased prevalence of shedding in multivariable modelling were the use of calf scour prophylaxis in cows (risk ratio [RR] 1.70, P < 0.01) and calves (RR 1.38, P = 0.02) and the feeding of milk replacer in the first week of life (RR 1.40, P = 0.02). In contrast, the presence of concrete flooring in calf housing areas (RR 0.59, P < 0.01) and the use of soap or detergent when washing calf feeding utensils (RR 0.61, P < 0.01) appeared to be protective.