OVMC were isolated by artificial digestion with the pepsin and
sedimentation method, as has previously described elsewhere (Pinlaor
et al., 2013). 0.33 or 0.40 kg of pla-som from each experimental groups
1 and 2, respectively, was mixed with 0.25% pepsin–1.5% HCl in 0.85%
NaCl solution and then homogenized using a blender. Each mixture
was incubated at 37 °C in a shaking water bath for 1 h. The digested
materials were passed through sieves with different pore sizes (1000,
300, 106 and 250 μm) and then washed with 0.85% NaCl in a sedimentation
jar until the supernatant became clear. Viable OVMC were determined
by observation of the size of cysts under a stereomicroscope, as
well as by the presence of a double-walled cyst, oval shape, clearly
defined oral and ventral suckers, and display of vigorous movement
within the cyst. Degeneration of metacercariae was determined by
incomplete or destroyed str