Detection of Cryptosporidium oocysts in fresh and frozen cattle faeces:: comparison of three methods

Aims: The aim of this study was to compare the performance of three commonly used screening tests for Cryptosporidium oocysts in fresh and frozen cattle faeces. Methods and Results: Twenty-nine freshly voided faecal samples were collected from calves from three farms in the northwest of England. Three diagnostic tests for Cryptosporidium were carried out on each sample both before and after freezing - the modified Ziehl-Neelsen (MZN) and auramine phenol (APh) stains and a commercial enzyme immunoassay (EIA) kit, the ProSpecT Cryptosporidium Microplate assay (Remel, Lenexa, KS). Twelve samples were deemed positive by the reference standard (polymerase chain reaction, PCR). There were some discrepancies between the results of the screening tests and the levels of agreement were quantified. The sensitivity and specificity of each method was determined, with PCR as the gold standard. Sensitivity and specificity of the MZN stain was optimized when samples with fewer than two oocyst-like bodies were classified as negative. Conclusions: All three screening methods used were effective in detecting Cryptosporidium infection in both fresh and frozen calf faeces. Significance and Impact of the Study: This study has highlighted the value of determining characteristics of tests used for diagnosis and epidemiological studies.