| Summary: | 碩士 === 國立中興大學 === 獸醫學系 === 85 === The Sun Moon Lake, located at Nan-Tou country in Central Taiwan,
is a known endemic area for clonorchiosis. From October 1995 to
March 1997, 745 specimens of Hemiculter leucisculus, 21
Cirrhinus molitorella,4 Misgurnus anguillicaudatus and 8 Tilapia
zillii collected from Sun MoonLake were examined. A total of
88,181 metacercariae was collected from the 745 H. leucisculus.
Of the 80,961 metacercariae that were examined under light
microscopy, 79,280(97.92%) were found to belong to Haplorchis
taichui, 90 (0.11%) to H. Pumilio, 73 (0.09%) to Clonorchis
sinensis and 1,518 (1.88%) to unknown species due the
metacercariae being not yet developedor immature and possibly
might have been dead and degenerated. A total of 2,168
metacercariae was collected from 21 C. molitorella. Of the 208
metacercariae that were examined, 198 (95.19%) were found to
belong to H. taichui and 10 (4.81%) to unknown. A total of 9
metacercariae was collectedfrom 3 T. zillii and the other 5 T.
zillii were uninfected with any metacercariae. Of the 9
metacercariae that were examined, they were all found to be H.
taichui. No metacercariae was found from the 4 M.
anguillicaudatus. Excystation of the metacercariae after pepsin
digestion could be accelerated by using trypsin, pancreatin or
changing the pH valueof the medium, for easy identification. No
obvious tissue reaction wasobserved around the metacercariae in
the infected fishes. In experimental infection to study
the final hosts range ofHaplorchis taichui, rodent hosts were
found to more susceptible Than feline hosts. In experimentally
infected rodent hosts, BALA/c mice were found to harbour more
trematodes than rats and hamsters. In BALB/c mice and in rats
injected with prednisolone, more trematodes were recovered than
the non-injested animals. However, injection of dexamethasone
did not increase the recovery of the worm from the
experimentally infectedrodents. Adult worm of H. taichui could
be recovered from the intestine of an experimentally infected
night heron. This shows that fish-eatingbird can serve as the
final host of H. taichui. However, no trematodecould be
recovered from Mallard duck(Anas platyrhynchos), Mule duck
andchicken (Leghorn). Thus galliform bird and fish could not
possibly serve as the final host for H. taichui. Metacercariae
just need 4 days to be gravid after infecting the final hosts.
In histopathological observationof parasitic parts in final
hosts' small intestine, it just showedpressure atrophy in the
neighbouring villi and little secretion of the mucosa between
the worm.
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