A comparison of dichromate solution floatation and fecal smears for diagnosis of cryptosporidiosis in calves.

Fecal samples from eleven calves experimentally infected with cryptosporidia were examined by two methods to evaluate their sensitivity and ease of use as diagnostic techniques. Comparison of a dichromate solution floatation and fecal smear techniques indicated that the former method was more sensitive. Oocysts were detected in feces earlier and for a longer period following exposure, and were easier to visualize using the dichromate solution floatation procedure. In addition, the dichromate solution floatation technique eliminated Candida albicans which can sometimes be confused with cryptosporidial oocysts in fecal smears. Another advantage was that oocysts could readily be detected in fecal samples stored as long as 120 days in dichromate solution. Using the dichromate solution floatation technique, it was shown that shedding of cryptosporidial oocysts in feces occurred from two to 20 days after oral challenge but was not always accompanied by diarrhea. Infection with cryptosporidia was confirmed in two calves at necropsy. Calves which were not sacrificed for portmortem examination recovered without treatment. The dichromate solution floatation technique is simple, rapid, inexpensive and should facilitate detection of cryptosporidia by diagnostic laboratories and some veterinary practitioners.