EFFECT OF 3 CONCENTRATION TECHNIQUES ON VIABILITY OF CRYPTOSPORIDIUM-PARVUM OOCYSTS RECOVERED FROM BOVINE FECES

Bovine fecal samples (1 g) negative for Cryptosporidium sp. oocysts we re seeded with 7 x 10(4) Cryptosporidium parvum oocysts and purified b y either water-ether concentration, sucrose density flotation, or zinc sulfate flotation to evaluate oocyst recovery. The effect of these pu rification techniques on the viability of recovered oocysts was also e valuated, Significantly higher numbers of seeded oocysts were recovere d by water-ether concentration (recovery rate, 46 to 75%) than by sucr ose density (24 to 65%) or zinc sulfate (22 to 41%) flotation methods. In addition, water-ether concentration did not exert a significant ef fect: on the viability of the population of oocysts recovered, whereas sucrose density flotation and zinc sulfate flotation selectively conc entrated viable oocysts. The water-ether concentration procedure is re commended for use in epidemiological studies in which both oocyst enum eration and viability assessment are required.