| Summary: | 碩士 === 國立臺灣大學 === 動物學系 === 84 === White spot syndrome associated virus (WSSV) is the
causative agent of a disease causing mass mortalities of
cultured shrimps. The detection of WSSV has been performed
by polymerase chain reaction (PCR). The sensitivity of two-
step PCR with nested primers was found to be higher than that
of one-step PCR alone, one-step PCR with southern blot, and
one-step PCR with dot blot, and so two-step PCR was used in
the subsequent parts of this study. Except for the
hepatopancreas and nerve tissues, WSSV was present in the other
organs of the seriously infected spawners; in the lightly
spawners only of the organs were positive in two-step WSSV
PCR; all the organs of the uninfected spawners were WSSV
negative in two-step WSSV PCR. Using a light
microscope to observe histopathological changes in
seriously infected spawners, degenerated cells were
found to be characterized by hypertrophied nuclei
being stained homogeneously in some organs. This phenomenon
was particularly distinct in the cuticular epidermis.
We used in situ hybridization to confirm that the cell
degeneration was caused by WSSV. Each cell with a clearly
hypertrophied nuclei gave a positive signal and
degenerated cells with non-obviously hypertrophied nuclei
were also positive, and were thus rendered distinguishable
from normal uninfected cells. Using in situ hybridization,
some of the follicle cells, oogonia and chromatin nucleolus
oocytes in the ovary of the seriously infected spawners
were found to be infected by WSSV. From July 1995 to February
1996, 48 broodstock specimens of P. monodon were caught from
the wild. Six of these were positive in one-step WSSV PCR and
30 were positive in two-step WSSV PCR, giving a rate of
infection of 62.5%.
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