This study reports further observations on encystment and excystment of the paramphistomid trematode Zygocotyle lunata. Of numerous substrates tested in the laboratory for cercarial encystment, i.e.
plastic and glass dishes, Styrofoam™,
aluminium foil, snail shells, and cheesecloth, all but cheesecloth allowed for 100% encystment within 4 h of cercarial release at 28°C. Numerous physical and chemical factors were tested to kill
cysts, and their capacity to do so was determined by the subsequent inability of
cysts to excyst within a chemical excystment medium.
Vinegar, Italian salad dressing, soy sauce and 10% solutions of
sucrose,
acetic acid and
sodium chloride were the most detrimental. Freezing, boiling and storage of
cysts for more than 2 years also killed them. Several marinades such as lemon juice, Worcestershire sauce, and various concentrations of
potassium permanganate, did not kill the majority of
cysts tested. Since Z. lunata is a potential foodborne trematode for humans and animals, it is important to determine suitable ways to control or kill these
cysts.