Isolation and enumeration of Giardia cysts, Cryptosporidium oocysts, and Ascaris eggs from fruits and vegetables

Published techniques for recovering parasites from fruit and vegetables are generally inadequate, with low and variable recovery efficiencies. Here we describe an improved methodology for analyzing fruit and vegetables for Gi ardia cysts, Cryptosporidium oocysts, and Ascaris eggs. The method includes washing procedures, sonication, and, for Giardia and Cryptosporidium, immu nomagnetic separation. Identification is by immunofluorescence (Giardia and Cryptosporidium) or brightfield microscopy (Ascaris). Recovery efficiencie s from lettuce, Chinese leaves, and strawberries were found to be approxima tely 67% for Giardia, 42% for Cryptosporidium, and 72% for Ascaris. Recover y efficiencies from bean sprouts tended to be more variable and lower. This could be due to material removed with the parasites during the washing pro cedures, which, in turn, appeared related to the age of the bean sprouts. I t is therefore recommended that fruit and vegetables should be as fresh as possible when analyzed for parasites.