Environmental Load of Cryptosporidium parvum Oocysts from Cattle Manure in Feedlots from the Central and Western United States.

The article presents information on a study to quantify the environmental load of Cryptosporidium parvum oocysts in fecal material deposited by feedlot cattle from across the central and western U.S. during a 22-month period. Another objective of the study was to genotype isolates of C. parvum from feedlot cattle to help facilitate proper identification of mammalian sources of waterborne C. parvum. Veterinary Medical Officers of the U.S. Department of Agriculture, Animal and Plant Health Inspection Services, Veterinary Services, and academic faculty identified one to four cattle feedlots in their respective states for cooperation on this project for a total of 22 feedlots in 7 states of the U.S. Direct immunofluorescent microscopy (DFA) was used as the primary diagnostic procedure for detecting and enumerating C. parvum oocysts in fecal samples collected from these feedlots. In addition to DFA for routine screening of fecal samples, immunomagnetic separation of oocysts coupled with direct immunofluorescent microscopy was performed on 10 randomly chosen DFA-negative samples per feedlot.