Disinfection with hydrated lime may help manage cryptosporidiosis in calves.

Diarrhea is common in young calves and is often caused by Cryptosporidium parvum infection. The aim of this study was to investigate if disinfection of calf pens with hydrated lime would reduce contamination of C. parvum oocysts and improve calf health in herds with C. parvum associated diarrhea problems. Four dairy herds with ongoing C. parvum associated calf diarrhea problems each participated in the study over six to seven months. During the study period, all pens/huts for young calves were cleaned according to the usual farm routine before a new calf entered. Hydrated lime was then used to disinfect half of the pens/huts. Diarrhea incidence was recorded by the farmers and by veterinarians, who clinically examined the calves every second month. In total, 402 calves participated in the study. The farmers detected diarrhea in 214 (53%) calves, with similar proportions in calves kept in lime disinfected and control pens. Age at diarrhea onset was significantly higher in lime disinfected pens than in control pens, 9.0 days and 7.6 days, respectively. There was no difference between the groups regarding duration or severity index recorded by the farmers. The body condition score in 6-8 week old calves was significantly higher in calves that had been kept in lime disinfected pens during their first weeks of life, indicating that calves in disinfected pens/huts were less affected by their infections. Faecal samples from 5 to 21 day old calves, were collected on four occasions at each farm (n = 95). Cryptosporidium positive samples were found at all samplings in all four herds. Cryptosporidium spp. was detected in 79 (83%) samples with no difference between lime disinfected and control pens. C. parvum was the dominant species. Two different C. parvum subtypes were found; IIaA16G1R1b in three herds and IIaA16G1R1b_variant in one herd. Only one subtype was found in each herd. Disinfection of calf pens with slaked lime delayed onset of diarrhea and improved the body condition in the calves, but did not affect diarrhea incidence or duration. Although lime disinfection alone will not be sufficient to control Cryptosporidium associated diarrhea in herds with extensive calf diarrhea problems, these results suggest that it can be a valuable complement to other measures.