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SUMMARYOne hundred faecal specimens, randomly collected from various locations within seven public parks in the west of Scotland, were examined for the presence of Giardia sp. cysts and Cryptosporidium sp. oocysts. Eleven percent of samples contained Giardia sp. cysts and 1 % contained Cryptosporidium sp. oocysts. Occurrence data from individual parks varied from 0 to 40 % for Giardia and 0 to 2 4 % for Cryptosporidium. The occurrence of parasitic organisms in public parks, especially in the vicinity of children's playing areas is a matter of concern for public health officials and regulators of leisure and recreation amenities.

Cryptosporidium parvum oocysts were exposed to ozone using two experimental systems. The first method involved producing residual concentrations of 1, 3 and 5 mg/L of ozone in 500 ml of water in a Drechsel gas bottle, which was then inoculated with oocysts. The second method involved inoculating 7 L of water with oocysts and then applying a constant dose of 1, 3 and 5 mg/L of ozone, circulating the water in a contactor system. Viability was assessed by the inclusion/exclusion of fluorogenic vital dyes. Comparison of these two methods showed that the second method was considerably more successful at reducing oocyst viability than the first method. Experiments performed at an increased temperature using method one indicated that temperature was an influencing factor on oocyst inactivation by ozone treatment.

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