DETECTION OF CRYPTOSPORIDIUM-PARVUM OOCYSTS IN FECES - COMPARISON OF CONVENTIONAL COPROSCOPICAL METHODS AND THE POLYMERASE CHAIN-REACTION

Conventional and coproscopical methods were compared with the polymera se chain reaction (PCR) for the detection of Cryptosporidium oocysts i n bovine faeces. Oocysts were not detected in samples seeded with 10 0 00 oocysts following formol ether sedimentation and examination using auramine phenol (AP) or by immunofluorescent (IF) staining. When oocys ts were concentrated using sucrose flotation the threshold of detectio n was 4000 oocysts per gram for both staining methods. Following salt flotation 4000 oocysts per gram could be reliably detected by AP stain ing but the detection limit was increased to 6000 oocysts per gram usi ng IF staining. The recovery of oocysts was significantly less than ex pected for all techniques. A specific PCR coupled with immunomagnetic particle separation (IMS) of samples detected dye oocysts per mi of di luted faeces, which corresponds to 80-90 oocysts per gram. Even allowi ng for the dilution of formed faecal samples, required for IMS, this r epresents an increase in sensitivity of several orders of magnitude ov er the conventional corpodiagnostic methods.