This study was carried out to observe in vitro effect of praziquantel on the tegumental changes of Heterophyopsis continua with scanning electron microscope. Metacercariae were collected from the perch, Lateolabrax japonicus, by artificial digestion techniqne and fed to 2-week old chickens. Adult worms were recovered from small intestine of chickens 8 days after infection. For working solutions, praziquantel was diluted with TC199 medium at concentration of 0.01, 0.1, 1 and l0㎍/㎖. To each petri clish containing l0㎖ of solution, 5∼10 worms were introduced and incubated at 37℃.
For the scanning electron microscopy(SEM), the worms were fixed in cold 2.5% glutaraldehyde, dehydrated in a series of graded ethanol and freeze-dried. Dried specimen was mounted on stub and coated with gold and observed in an SEM. The results were as follows:
1. Severe tegumental alterations were recognized by scanning electron microscope. Bleb formation of tegument was observed in 5 minute group and most pronounced on anterior tegument of worms. The number and size of blebs increased as incubation time prolonged.
2. The surface destruction was more pronounced at ventral margin between the oral and the ventral suckers.
3. The sensory papillae were slightly affected, but destruction of tegumental spine was not recognized.
4. The effect of praziquantel on the worm was found dependent on the concentration and incubation time, however, the effect was more dependent upon the incubation time.
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