EVALUATION OF COMMERCIAL ENZYME-IMMUNOASSAY (EIA) AND IMMUNOFLUORESCENT ANTIBODY (IFA) TEST KITS FOR DETECTION OF CRYPTOSPORIDIUM OOCYSTS OF SPECIES OTHER THAN CRYPTOSPORIDIUM-PARVUM

A commercial enzyme immunoassay (EIA) (ProSpect(R) Rapid Assay), a dir ect immunofluorescence antibody (IFA) test for stool testing (MERIFLUO R(TM) Cryptosporidium/Giardia), and an indirect IFA test for environme ntal testing (Hydrofluor(TM)-Combo Cryptosporidium/Giardia) were evalu ated for detection of low public health risk Cryptosporidium oocyst is olates, and for C. parvum oocyst isolates from human and bovine feces that represent a high public health risk. There was no cross-reactivit y of the EIA with ova of eight medically important helminths, three Ei meria species oocysts, Sarcocystis cruzi sporocysts, and two Candida s p. isolates. All nine snake oocyst isolates (C. serpentis), two of sev en lizard oocyst isolates, one turtle oocyst isolate, two avian oocyst isolates (turkey, C. meleagridis), one C. wrairi oocyst isolate from guinea pigs, one C. muris oocyst isolate from hyrax, one heifer C. mur is isolate, and two C. muris-like oocyst isolates from a camel were po sitive by both IFA tests; six of these 19 oocyst isolates were EIA-pos itive. There was no difference in the sensitivity and specificity betw een direct and indirect IFA tests. The sensitivity of the EIA and both IFA tests to the C. parvum oocysts was 100%. The EIA showed less cros s-reactivity with the non-C. parvum oocysts (24%) than direct or indir ect IFA (76%), and was less sensitive to those isolates (20%) than bot h LFA tests (63%). A simulated sampling model for high and low public health risk Cryptosporidium oocysts showed that the low risk oocyst is olates may constitute up to 35% of all positive environmental samples by direct or indirect IFA determination, and up to 12% of all EIA posi tive samples. This study indicates a superiority of direct and indirec t IFA and EIA for screening of human-or-bovine-origin fecal specimens, whereas testing of environmental samples may lead to misidentificatio n of medically important isolates. The results demonstrated that the E IA kit can more accurately identify environmental samples containing o ocysts pathogenic for humans than both IFA tests. The specificity of c ommercially available diagnostic kits to C. parvum should be criticall y examined for cross-species identification before they are recommende d or adopted for use in testing environmental samples.