A Swedish study reported in the March 2013 Journal of Epidemiology & Infection indicates that there is a similar prevalence of Cryptosporidium spp. in organic and conventional dairies.
C. Silverlas and I. Blanco-Penedo sampled 221 calves and 259 cows from 13 organic and 13 conventional dairy herds, as well as gathering management information from those farms.
Their study indicates that prevalences were similar in organic and conventional calves (44.7% vs. 52.3%), as well as in cows (3.1% vs. 3.8%), P > 0·05. Cryptosporidium bovis, C. ryanae and C. parvum were identified.
The Center for Food Security and Public Health at Iowa State University says that cryptosporidiosis mainly occurs in very young animals. Among calves, one- to three-week-old animals seem to be most susceptible. Clinical signs may include anorexia, diarrhea, tenesmus and weight loss. More severe disease can occur with concurrent infections. Animals can also be colonized without symptoms.
Read the abstract in the Journal of Epidemiology & Infection.