Comparison of an acid-fast stain and a monoclonal antibody-based immunofluorescence reagent for the detection of Cryptosporidium oocysts in faecal specimens from cattle and pigs.

A commercially available direct immunofluorescence (IF) assay with monoclonal antibodies (Monofluo Kit Cryptosporidium, Diagnostics Pasteur, France) was compared with the modified Ziehl-Neelsen (MZN) acid-fast technique for the detection of Cryptosporidium oocysts in faecal samples from cattle and pigs. Stool specimens individually collected from 108 bovines and 90 pigs were examined in a blind test. The results of the two procedures corresponded (both positive or negative) in 102 (94.4%) cattle samples and 80 (88.9%) pig faecal samples. However, the remaining six (5.5%) cattle specimens and 10 (11.1%) pig stool samples, all of them harboring few oocysts (0-1 oocysts per 20 x field), were negative by MZN and positive by IF. False-negative results of the acid-fast stain occurred in suckling (17.2% of discrepant results) and weaned calves (2.9%) as well as weaned piglets (43.7%) and fattening pigs (10%). Stool specimens from the remaining age groups were negative by both techniques. The MacNemar's chi-square test showed that differences between both methods were statistically significant (P < 0.05). Compared with immunofluorescence procedure, the sensitivity of MZN technique in samples from cattle and pigs was 79.3% and 67.7% and the negative predictive value was 92.9% and 85.5% respectively. The specificity and positive predictive values of the acid-fast stain were 100% in both animal species. It is concluded that the monoclonal antibody-based immunofluorescence reagent evaluated is more efficient that the MZN technique, especially for detecting a low number of Cryptosporidium oocysts, in faecal specimens from both cattle and pigs.