Infection pattern of Cryptosporidium and Giardia in calves.

Faecal samples were collected weekly over a 3 month period from 0- to 20-week-old calves on an Ohio dairy farm, and examined for Cryptosporidium oocysts and Giardia cysts by a quantitative direct immunofluorescence assay. Oocysts and cysts were detected as early as 4 days of age. Shedding of Cryptosporidium oocysts peaked at 1 week and was low by 3 weeks. Some calves, however, continued to pass low numbers of oocysts. Shedding of Giardia cysts peaked at 2 weeks of age with high levels maintained until 7 weeks of age. Most calves continued to pass low numbers of Giardia cysts after weaning. Cumulative infection rates for both Cryptosporidium parvum and Giardia sp. were 100%.