2005 Fiscal Year Final Research Report Summary
Worm expulsion and large intestine parasitism of Strongyloides ratti as the survival strategy
| Project/Area Number |
15590376
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Parasitology (including Sanitary zoology)
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| Research Institution | Aichi Medical University |
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Principal Investigator |
KIMURA Eisaku Aichi Medical University, School of Medicine, Professor, 医学部, 教授 (70153187)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHINO Masataka Aichi Medical University, School of Medicine, Professor, 医学部, 教授 (70046077)
ITOH Makoto Aichi Medical University, School of Medicine, Associate Professor, 医学部, 助教授 (90137117)
KADOSAKA Teruki Aichi Medical University, School of Medicine, Instructor, 医学部, 講師 (90109760)
KONDO Shigeo Aichi Medical University, School of Medicine, Instructor, 医学部, 講師 (20097786)
TAKAGI Hidekazu Aichi Medical University, School of Medicine, Assistant, 医学部, 助手 (90288522)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Strongyloides ratti / host-parasite relationship / worm expulsion / anti-oxidant |
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| Research Abstract |
It has been believed that Strongyloides ratti parasitizes only in the small intestine (SI) of rats, and expelled in ca. 2weeks. We reported that, following worm expulsion, a few parasite re-establish parasitism in the large intestine (LI), and that eggs produced by LI adults underwent the indirect way of development, producing free-living males and females. This development eventually produced far more infective larvae than SI adults. We hypothesized that S. ratti would have innate strategies to survive or even utilize host defense mechanisms.
1.LI parasitism in wild rats
The above hypothesis was questioned because no LI parasitism in wild rats has been reported. We examined wild rats captured in Nagoya, and found that 32.4% of them had infection in the LI. The average number of worms in the LI was only 4.7/rat. However, an additional experiment revealed that the 4.7 adults produced 4,638 infective larvae per day. The number of LI parasites increased in the spring, when temperature allow
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s free-living development, suggesting a biological significance of the LI parasitism.
2.Effect of anti-oxidant BHA on LI parasitism
When BHA was added to daily food for experimental rats, it abolished completely the LI parasitism without influencing the SI parasitism.
3.Transplanting SI adults of different days after infection into the LI
This study is going on. The results obtained so far suggest that regardless of the site of parasitism, host immunity seemed to reduce the number of intrauterine eggs and enhance the indirect development of eggs outside a host. The LI parasitism reduced body length of parasite and the number of intrauterine eggs.
4.Electron microscopical study
The intestinal tract of adult S. ratti parasitizing in host SI was swollen and filled with "food debris", while that of adult S. ratti in the LI was compressed and empty. Intestinal cells of SI adults had many mitochondria, while those of LI adults did not, but had plenty of rough endoplasmic reticulum. These apparent difference seems to be related to ‘fasting' of worms. Less
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