Excystation of Haplorchis taichui metacercariae could be elicited by change in pH

The effect of different component of the intestinal fluid on the excystation of Haplorchis taichui metacercariae was examined in vitro. Encysted metacercariae obtained by pepsin digestion of fish muscle showed that the highest percentage of metacercariae excystation could be obtained after being treated with trypsin at pH 7.5. However, it was also observed that excystation of the metacercariae could also be effected by changing the pH to the basic condition. The most optimum pH for the metacercariae excystation was found to be 7.5. This method of obtaining the excysted metacercariae could prove to be useful for taxonomical study of trematode in general.