Prevalence of Cryptosporidium muris-like oocysts among cattle populations of the United States: preliminary report.

As part of a national survey for bovine, Cryptosporidium muris oocysts, fecal smears in the form of up to 144, 3- to 5-mm dots per glass slide were prepared from pen samples at dairies and feedlots in the eastern and western United States. Acid-fast staining was followed by light microscopic evaluation at x100. Samples from 150 dairies numbered 48,810 and those from 30 feedlots, 47,064. Positive samples were found at 102 (68%) dairies and 24 (80%) feedlots. Overall, prevalence of positive samples by state was up to 4.7% (Virginia dairies), but within certain pens of cattle, 31% (Connecticut dairy) and 11.8% (California feedlot) of the samples were positive.