Significance of small numbers of Cryptosporidium sp oocysts In water

The Cryptosporidium Problem in Water and Food Supplies

“…Low concentrations may often be detected in potable water with no evidence of disease, although the waterborne route may be implicated when clusters of cryptosporidiosis cases are associated with the supply area for potable water. In one U.K. study, it was reported that on the occasions when there were detectable levels of Cryptosporidium in one particular water supply (0.002 -0.024 oocysts per L) there was no increase in cases of cryptosporidiosis in the community above background level, and in the water source, which was analysed over a period, viable oocysts occurred only rarely (29). Contamination of potable water supplies may either contribute to an endemic level of disease or an increased level of immunity in the exposed population, or both (30).…”

An outbreak of cryptosporidiosis in South London: what value the p value ?

“…New techniques to enable such discrimination are being developed [11]. Indeed in a Scottish study using Restriction Fragment Length Polymorphism (RFLP) techniques, viable oocysts were found rarely in the particular water source studied and their presence was not associated with an increased risk to health [12]. The detection of oocysts in raw water is of itself not unexpected and studies have shown oocysts in 7-8 % samples examined [13].…”

Genotype analysis of Cryptosporidium spp. prevalent in a rural village in Hwasun-gun, Republic of Korea

“…Ingestion of only small numbers of viable Cryptosporidium oocysts could cause human cryptosporidiosis (Smith et al, 1993). In the study area, water is supplied from a storage reservoir used by both villagers and domestic animals.…”