Cryptosporidium in drinking water - survey of occurrence. Final Report September 1991
Report No FR0226

D G Miller and E G Carrington

Sept 1991

SUMMARY

I OBJECTIVES

To assess the degree of occurrence, seasonal patterns and origins of cryptosporidium oocysts in a selected number of river and groundwater sources.

II REASONS

Outbreaks of cryptosporidiosis have been related to water supplies. The Badenoch Group of Experts recommended that information should be obtained on the degree of occurrence in water sources and that effort should be concentrated on an intensive survey of a few selected sources.

III CONCLUSIONS

The report presents the results of the survey of three river stretches and six groundwaters for the period of survey from January 1990 to March 1991. Over the period 1754 samples were analysed and of these 266 results were subjected to quality assurance.

The results overall show a low incidence of oocysts in the sources surveyed. Only one river stretch gave consistent positive results albeit at low levels.

On the river giving positive results correlations were found with rainfall, river flow and season.

In parallel epidemiological studies, which are still continuing, a low incidence of cryptosporidiosis was found in the communities examined.

Compared with studies on surface waters in the United States the levels found in the study are much lower, particularly when compared with the large industrialised rivers surveyed in the US work.

IV RECOMMENDATIONS

Towards the end of the study the question of continuation was discussed. In view of the largely negative results obtained and the fact that further studies were planned by the NRA on a river subject to agriculture pollution and by the Foundation for Water Research on Loch Lomond, it was agreed that the national survey would not be extended further.

Copies of the Report are available from FWR, price 15 less 20% to FWR Members.