Survival of Cryptosporidium parvum in faecal wastes and salad crops

Warnes, S. and Keevil, C.W. (2003) Survival of Cryptosporidium parvum in faecal wastes and salad crops. In, Duffy, G. (ed.) Cryptosporidium parvum in Food and Water. Dublin, IE. Teagasc, pp. 15-24.

Abstract

Cryptosporidium parvum is a protozoan parasite of man and a range of animals. An essential stage of the life cycle is the formation in the gastrointestinal tract of oocysts, each containing four infectious sporozoites. Thick wall oocysts are shed in apparently normal or diarrhoetic faeces to contaminate soil and water, providing routes into the food chain. Desiccation and snap freezing are lethal to oocysts. Nevertheless, the robust coat affords significant protection against environmental stressors such as low pH or water activity, temperatures above freezing and a range of sanitising and oxidizing agents such as chlorine. C. parvum may therefore survive in the environment for extending periods of time, posing a threat to animals and man if ingested either directly in contaminated water or in uncooked/ improperly cooked foods which are cropped from contaminated land. This threat has only partially be characterized, due in part to the difficulty in recovering oocysts and other pathogens from complex matrices such as manures and salad leaf surfaces.

Accordingly, this study describes improved methods for the recovery of oocysts from faecal waste samples and salad crops, with recovery efficiencies of 40-80%. Using these improved tools, the results of oocyst survival studies in the stored wastes and on salad leaves are presented to show the suitability and drawbacks of current practices to minimize entry and spread of C. parvum in the food chain

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Contributors

Author: C.W. Keevil

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