Prevalence of Cryptosporidium parvum infection and pattern of oocyst shedding in calves in Japan

Cryptosporidium parvum infection and the pattern of oocyst shedding were observed in calves, A total of 480 fecal samples were collected from 30 calves (age. less than or equal to 30 days) over a period of 10 months from June 1998 to March 1999. A sucrose centrifugal flotation technique revealed 28/30 (93%) calves were passing Cryprosporidium oocysts. Oocyst shedding was first detected on the sixth day after birth, with 8% of the calves testing positive. This rate increased day by day and reached approximately 80% by day 15. Oocyst shedding varied from 1 to 13 days, with a mean of 7 days. Calves infected with C. parvum had a significantly higher rate of diarrhea (33%) than non-infected calves (8%) (P< 0.05), suggesting C. parvum infection as the likely cause. The mean number of oocysts excreted by calves <less than or equal to> 30 days old was approximately 6 x 10(7) per gram of feces. These results indicated that one calf would excrete some 6 x 10(11) oocysts in the first month after birth, taking both the quantity of feces in a day and the period of excretion into consideration. Accordingly, it is clear that calves are important in the spread of cryptosporidiosis to calves and humans. (C) 2000 Elsevier Science B.V. All rights reserved.