Sensitivity of ELISA for detecting Cryptosporidium spp. and Giardia spp. in raw waters samples

Abstract

The microscopic methods for detecting Cryptosporidium and Giardia are expensive, and a variable reproducibility and a low recovery are found. Nevertheless, a rigorous technical standardization and a quality control in the recovery testing give support to use them for analyzing the environmental samples. This study determined the sensitivity of ELISA for analyzing Giardia spp. and Cryptosporidium spp. in raw water samples. Also, it was investigated whether this assay could be used as a screening test for detecting Giardia cysts and Cryptosporidium oocysts in raw water samples; and to deduce the potential transmission of giardiasis and cryptosporidiosis from these specimens. The detection limits were high, being 98 cysts and 3.492 oocysts. Of the analyzed environmental samples, 20 % showed ELISA positive for Cryptosporidium spp., and none for Giardia spp.. Therefore, ELISA showed to be unsuitable to be used as screening assay, because in the environmental samples usually occur a lower numbers of oocysts and cysts than those regularly found in infected stool samples, for which these kits have been validated. Furthermore, the dilutions prepared from the stock solutions of cysts and oocysts in distilled water could have resulted in unfavorable reaction conditions, and it has affected the sensitivity of ELISA.