2007 Fiscal Year Final Research Report Summary
Mechanism of pathogenicity manifestation by fish parasites through host switching
| Project/Area Number |
17380114
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | The University of Tokyo |
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Principal Investigator |
OGAWA Kazuo The University of Tokyo, Graduate School of Agricultural and Life Sciences, Professor (20092174)
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| Co-Investigator(Kenkyū-buntansha) |
URAWA Shigehiko Nat. Salmon Resources Center, さけますセンター・さけます研究部, Chief Scientist (60425460)
YOSHINAGA Tomoyoshi The University of Tokyo, Graduate School of Agricultural and Life Sciences, Associate Professor (20345185)
YOKOYAMA Hiroshi The University of Tokyo, Graduate School of Agricultural and Life Sciences, Assistant (70261956)
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| Project Period (FY) |
2005 – 2007
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| Keywords | Fisheries Science / Fish Pathology / Fish parasite / Pathogenicity / Host switch |
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| Research Abstract |
In order to elucidate mechanisms of new disease outbreaks through host switch by fish parasites, infection experiments were conducted using natural and unnatural fish hosts and susceptibility among different host fish species was analysed and infection dynamics were compared.
1) Pseudodactylogyrus bini and P. anguillae (Monogenea) of eels: Infection experiments were carried out of Japanese and European eels with the two species of monogeneans and infection dynamics were compared by regular samplings. As a result, European eel, an unnatural host, was more heavily infected in terms of both prevalence and intensity than Japanese eel, and parasites grew faster on the former eel than on the latter.
2) Heterobothrium okamotoi (Monogenea) of tiger puffer: Settlement rates of hatched larvae (oncomiracidia) of the parasite on the host were compared among many marine fishes including tiger puffer, the natural host. It was revealed that the oncomiracidia selectively settled on the gills of fishes o
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f the genus Takifugu, suggesting its high host specificity upon settlement. It was also suggested that more than one factor was involved in inducing oncomiracidial settlement on the gills in the process of host selection by H. okamotoi.
3) Enteromyxum leei (Myxozoa) of tiger puffer: Infection experiments show that Japanese flounder, red sea bream and clownfish were as susceptible as tiger puffer, originally known host fish to the myxozoan, suggesting the possibility that the infection might spread to cultured fish other than tiger puffer and marine ornamental fish as well. Mortality and infection dynamics were affected by host size, salinity of rearing water and water temperature.
4) Kabatana takedai (Microsporea) of salmonid fishes: By exposing fish to water containing an unknown infectious stage of the microsporean, infection levels were compared among three strains of masu salmon, the natural host, and rainbow trout. Although no differences in the infection level were observed among the masu salmon strains, rainbow trout was more heavily infected in the heart muscle than masu salmon. It suggests the possibility that the parasite causes disease not only to masu salmon, but also to rainbow trout, an introduced fish from North America. Less
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