Prevalence of and risk factors for shedding of Cryptosporidium parvum in Holstein Freisian dairy calves in central México.

A total of 31 dairy farms from three states in central México were selected for this study in order to determine the prevalence of and risk factors for Cryptosporidium parvum shedding in young Holstein Freisian calves. Fecal samples were obtained once from each calf for acid-fast staining for detection of C. parvum oocysts. Information on each calf and on each dairy's management practices regarding the maternity pen, calf hutches and calf feeding was obtained by personal interview using a standardized questionnaire. Of the 31 dairies, 29 had one or more calves shedding C. parvum oocysts. The overall point prevalence was 25% (128/512). Dairy calves from the states of Hidalgo, Jalisco, and México had overall point prevalences of 28% (51/185), 29% (33/112) and 20% (44/215), respectively. Day of age was strongly associated with the risk of shedding C. parvum oocysts, with a maximum risk of shedding at approximately 15 days of age. Using mixed-effects logistic regression with herd as the random effect, feeding starter grain to calves, sweeping out the maternity pen, and using hay bedding in the maternity pen were significantly associated with increased odds of shedding C. parvum oocysts. We speculate that the association between feeding starter grain to calves and the higher odds of shedding C. parvum is linked to an increased duration rather than a higher incidence density of shedding. In addition, the association between sweeping the maternity pen and the increased odds of shedding C. parvum may be attributable to dairy personnel using the same broom for cleaning calf hutches and the maternity pen, thereby cross-contaminating oocysts from infected to newborn calves.