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Development and validation of a standard method to detect Cryptosporidium, Cyclospora and other parasitic protozoa on fruit and vegetables

Project Code: B09009

01/11/2012

Scottish Parasite Diagnostic Laboratory
Smith, H

The aim of this proposal was to develop validated standard method(s) to detect Cryptosporidium, Cyclospora and Giardia on fruit and vegetables.

Extraction of parasites from lettuce leaves and raspberries using aqueous liquid extractants was deemed to be the most variable component of the method and care was taken to optimise the extraction of seeded parasites using these extractants in order to maximise recoveries. Both molarity and pH played an important role in the release of parasites from the matrix into suspension. Of a total of 9 extractants tested, 1M glycine (pH 5.5) was selected for extracting Cryptosporidium parvum and Giardia duodenalis (oo) cysts from lettuce and 1M glycine (pH 3.5) for extracting C. parvum oocysts from raspberries. Standard Operating Procedures (SOPs) were developed to identify recovered parasites. The methods developed are user-friendly and, as far as possible, use equipment already available in accredited analytical laboratories. The methods were validated by a consortium of 8 UK accredited laboratories.

While other methods for detecting protozoan parasites on produce have been published, this is the first to be validated. The methods devised during the course of this project have been evaluated by interlaboratory collaborative trial, and the results should encourage their adoption as analytical tools. Data accrued using these sample sizes should prove useful in informing exposure assessments within risk analyses. Their development provides an important addition to the techniques and procedures available to combat the threat that protozoan parasites may pose to the food supply.

Final report

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