title: Quantitation of Giardia cysts and Cryptosporidium oocysts in fecal samples by direct immunofluorescence assay.
abstract: The lack of quick, simple, and sensitive quantitative tests has impeded studies on infection patterns and treatment of Giardia spp. and Cryptosporidium spp. A quantitative direct immunofluorescence assay (FA) using a commercial FA kit was developed and evaluated. Recovery rates of the FA for Cryptosporidium oocysts in calf feces seeded with 1,000, 10,000, 100,000, and 1,000,000 oocysts per g were 14.8, 40.8, 84.2, and 78.2%, respectively. Interassay coefficients of variation were 10.6 to 47.1%. Recovery rates of the FA for Giardia cysts in feces seeded with 1,000, 10,000, and 100,000 cysts per g were 76.4, 96.9, and 89.6%, respectively. Interassay coefficients of variation were 7.4 to 22.1%. By comparison, recovery rates of Giardia cyst by sucrose gradient flotation were only 20.5, 51.2, and 42.9%, respectively. Counts of cysts-per-gram obtained by sucrose gradient flotation with samples from calves, lambs, and ewes were only 49.1 to 54.8% of those obtained by the FA. Zinc sulfate flotation detected only 36.4% of infections when there were < or = 1,000 cysts per g. The quantitative FA offers a useful technique for epidemiological and control studies of these two parasites.
authors.affiliation: Department of Veterinary Preventive Medicine, Ohio State University College of Veterinary Medicine, Columbus 43210.
authors.forename: L
authors.initials: L
authors.lastname: Xiao
authors.forename: R P
authors.initials: RP
authors.lastname: Herd
mesh_terms: D000818:Animals; D002417:Cattle; D003458:Cryptosporidium / Q000302:isolation & purification*; D005243:Feces / Q000469:parasitology*; D005455:Fluorescent Antibody Technique; D005872:Giardia / Q000302:isolation & purification*; D010270:Parasite Egg Count / Q000379:methods*