Comparison of nested PCR and microscopy for the detection of cryptosporidiosis in bovine calves.

The comparative efficacies of different conventional parasitological methods and nested PCR for diagnosis of bovine cryptosporidiosis in faecal samples were evaluated. Among the 100 samples collected from calves in and around Ludhiana Direct faecal smear staining technique revealed 25.0 % positivity for the oocysts of Cryptosporidium spp. with sensitivity and specificity of 68.12 and 92.98 %, respectively. Zinc sulphate solution floatation and saturated sugar solution floatation staining techniques showed sensitivity and specificity of 83.92 and 96.36; 81.03 and 98.14 %, respectively. Products of the primary PCR of Cryptosporidium spp. directed against small subunit (18S) ribosomal RNA when employed as template in nested PCR produced the amplicons of desired size (834 bp) in 47.0 % of the samples. Amplification of 834 bp fragment was also observed in positive control, while no amplification was observed in negative control. Results indicated PCR assays as highly sensitive and specific techniques for the screening of the samples for Cryptosporidium spp. but in developing countries and under field conditions where limited resources do not allow the application of PCR assays, concentration staining methods are recommended.