碩士 / 國立海洋大學 / 水產養殖學系 / 84 / Outbreaks of a disease causing serious losses among
population of culturedPenaeus japonicus in Taiwan are
characterized by obvious white spots on the carapace,
appendages and the iside surface of the body.The diseased shrimp
alsodisplay signs of lethargy and reddish coloration of the
hepatopancreas.For thisreason,Chou et al.(1995) and Wang et
al.(1995)propose the name "white spot syndrome"(WSS).The present
study describes histopathological changes in tissuesfrom
diseased shrimp.Degenerated cells characterized by hypertrophied
nucleiwere observed in the cuticular epidermis and connective
tissue.Cellular necrosisand detachment of intestinal epithelium
tissue and severe atrophy of the hepatopancreasin diseased
shrimp were also observed.A non-occluded bacilliform viral
particlewas found by electron microscopy in the epidermis of
spontaneously infected shrimp.Virion were enveloped,330+20 nm in
length and 87+7nm in diameter. Filtrates prepared from the
epidermis of either diseased P. japonicus or diseasedP. monodon
were inoculated 4 established fish cell lines.Cytopathic effects
were not found in any of the 4 tested fish cell lines;the
filtrates which were used aswaterborne inocula had no
cytotoxicity.Healthy juvenile P. japonicus were immersedin
filtrates prepared from rither diseased P. monodon or diseased
P. japonicus,both exhibited marked white spot signs.Cumulative
mortalities reached 100% within5 to 7 days and white spots were
observed on the removed carapace of theseexperimentally infected
shrimp.Moribund shrimp were collected and examined by
transmission electon microscopy.The close resemblance in
extrenal signs and viralmorphology between spontaneously
diseased and experimentally infected shrimpindicated that the
bacilliform virus may be the main causative agent of the
diseasecharacterized by WSS in Taiwan.The virus was tentatively
designated as WSSV(whitespot syndrome associated virus)(Chou et
al.,1995; Wang et al., 1995). Shrimp infectivity test was
also carried out by means of oral ingestion.Obvious white spots
were observed on the exoskeleton of experimentally infectedyoung
P. mpnodon 2 days after being fed with muscle of diseased P.
monodon or P. japonicus.The results indicated that WSSV can be
transmitted orally as well asvia water across shrimp species.
Three sized groups of juvenile P. japonicus(meanweight
0.08g,0.16g and 0.26g respectively)were applied to infectivity
test of WSSV.The results revealed that the larger shrimp groups
were relatively low susceptibleto WSSV via waterborne
inoculation and the pathogenicity of WSSV were
significantlyaffected by catching and temperature stress.
Healthy P. monodon, P. japonicus and P. penicillatus were
immersed in filtratesfrom either diseased P. monodon or P.
japonicus.No difference was found in the pathogenicity of WSSV
from P. monodon and WSSV from P. japonicus.WSSV was foundhighly
pathogenic to the 3 tested shrimp species and was readily
transmitted acrossdifferent penaeid shrimp via waterborne
contant. Using PCR with a specific primer set(Lo et
al.,1996),WSSV was first detectedin the previously healthy P.
monodon immersed in filtrate from diseased P.monodon6 hours
postinoculation(HPI) and detected rate was 1/10(positive no./
tested no.).At 24 HPI and 48 HPI,the detected rates reached 9/10
and 9/9 respectively.Theappearence of WSSV in experimentally
infected P. penicillatus postlarvae was detectedat 24 HPI and
reached 100% at 72 HPI.Healthy young P. monodon fed with
diseasedP. japonicus as well as those fed with diseased P.
monodon became 70~90% WSSV-positive24 HPI and reached 100% at 48
HPI.With this specific primer and PCR,WSSV can be detected from
healthy-looking shrimp.The technique will be useful for the
screeningof carriers in shrimp larvae and parental spawners.
Pilot studies have shown that Helice tridens collected shrimp
farms are WSSV-positive by PCR with WSSV specific primer set.
| Identifer | oai:union.ndltd.org:TW/084NTOU0086015 |
| Date | January 1996 |
| Creators | Huang, Chang-Yi, 黃長義 |
| Contributors | Chou Hsin-Yiu, 周信佑 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 60 |
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