A Modified Digestion Procedure for Recovery of Trematode Metacercariae from Terrestrial Gastropods

Procedures for a digestion technique were modified to identify an optimum approach for recovering trematode metacercariae from large, terrestrial snails. Brachylaima thompsoni and Panopistus pricei were recovered via HCl/pepsin digestion from field-collected snails, Webbhelix multilineata and Neohelix albolabris. The incubation temperature, duration, concentration of digestion fluid, agitation, and centrifugation settings were modified until a set of procedures resulted in thorough digestion of the snail body while minimizing the required time to run the procedure and maximizing the fraction of metacercariae that remained alive and active. Most metacercariae died during lengthy digestions and/or thosewith high concentrations of HCl and pepsin. The optimal procedure identified included a 2 hr digestion in 0.7% HCl and 0.8% pepsin at 37 degrees C with initial cutting of the snail foot and periodic agitation during digestion. This method resulted in recovery of metacercariae that were nearly always alive and appeared no different than specimens recovered by direct dissection of snails. The method developed here is but one of many used for recovery of parasites, usually nematodes, from their invertebrate or vertebrate hosts, but it focuses on those characteristics that allow live trematode recovery.