Efficacy of beta-ray irradiation in inactivating pathogenic protozoa

• Project/Area Number: 14550549
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Civil and environmental engineering
• Research Institution: Azabu University
• Principal Investigator: MORITA Shigemitsu Azabu University, Health and Environmental Sciences, Assistant Professor, 環境保健学部水環境学研究室, 講師 (50318888)
• Co-Investigator(Kenkyū-buntansha): HIRATA Tsuyoshi Azabu University, Health and Environmental Sciences, Professor, 環境保健学部, 教授 (50005493)
• Project Period (FY): 2002 – 2004
• Project Status: Completed (Fiscal Year 2004)
• Budget Amount: ¥3,400,000 (Direct Cost: ¥3,400,000); Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000); Fiscal Year 2003: ¥1,300,000 (Direct Cost: ¥1,300,000); Fiscal Year 2002: ¥1,200,000 (Direct Cost: ¥1,200,000)
• Keywords: Beta-ray / Inactivation / Protozoa / Cryptosporidium / Repair / Coexisting substances / 感染性 / 汚泥 / 動物感染性 / 生育活性

Research Abstract

Experimental studies on radioactive rays irradiation were conducted to determine the efficacy of inactivating C.parvum oocysts at various temperatures and intensities. The infectivity decreased exponentially as radiation doses increased. The gamma ray and beta ray doses resulting in a 2 log_<10> reduction in infectivity were 94 Gy and 92 Gy, respectively. Temperature and intensity did not significantly affect the efficacy of radioactive rays irradiation in reducing the infectivity of oocysts. Gamma ray and beta ray doses required for 2 log_<10> reduction in viability as evaluated using in vitro excystation were 13,000 Gy and 12,000 Gy, respectively. Thus, radioactive ray treatment resulted in oocysts that were able to excyst but not infect.
The potential of irradiated oocysts to recover infectivity by photoreactivation and dark repair was investigated.
In the inactivation of C.parvum by beta ray irradiation, high correlation was observed between number of single strand breaks and the dose of beta ray. The yield of single strand breaks formation was calculated to be 0.85/10^3bp per 100 Gy of 500 keV bata ray dose, which is in the same order as that calculated for E.Coli (0.9/10^3bp per 100 Gy of 500 keV bata ray dose).
There was no recovery in infectivity following treatment by fluorescent-light irradiation or storage in darkness.

Research Products

• [Journal Article] Inactivation of Cryptosporidium parvum oocysts by radioactive rays (2004)
  • Author(s): Morita S., Hirata T.
  • Journal Title: Proceedings of 4^<th> IWA World Water Congress and Exhibition (CD-R)
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Effect of the presence of coexisting substances on UV inactivation of Cryptosporidium parvum oocysts (2004)
  • Author(s): Morita S., Hirata T.
  • Journal Title: Proceedings of 2^<nd> Asia Conference on Ultraviolet Technologies for Environmental Applications (CD-R)
  • NAID: 130000099873
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Inactivation of Cryptosporidium parvum oocysts by radioactive rays. (2004)
  • Author(s): Morita S., Hirata T.
  • Journal Title: Proceedings of 4^<th> IWA World Water Congress and Exhibition (CD-R)
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Effect of the presence of coexisting substances on UV inactivation of Cryptosporidium parvum oocysts. (2004)
  • Author(s): Morita S., Hirata T.
  • Journal Title: Proceedings of 2^<nd> Asia Conference on Ultraviolet Technologies for Environmental Applications (CD-R)
  • NAID: 130000099873
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Inactivation of Cryptosporidium parvum oocysts by radioactive rays (2004)
  • Author(s): Morita S., Hirata T.
  • Journal Title: Proceedings of 4^<th> IWA World Water Congress and Exhibition (in CD-R)
• [Journal Article] Effect of the presence of coexisting substances on UV inactivation of Cryptosporidium parvum oocysts (2004)
  • Author(s): Morita S., Hirata T.
  • Journal Title: Proceedings of 2^<nd> Asia Conference on Ultraviolet Technologies for Environmental Applications (in CD-R)
  • NAID: 130000099873
• [Journal Article] Molecular characterization of a single Cryptosporidium oocysts in sewage by semi-nested PCR (2004)
  • Author(s): Hashimoto A., Sugimoto H., Morita S., Hirata T.
  • Journal Title: Proceedings of 4^<th> IWA World Water Congress and Exhibition (in CD-R)
• [Journal Article] Effect of ultraviolet irradiation on infectivity of Cryptosporidium parvum oocysts (2002)
  • Author(s): Morita, S., Namikoshi, A., Hirata, T., Oguma, K., Katayama, H., Ohgaki, S., Motoyama, N., Fijiwara, M.
  • Journal Title: Applied and Environmental Microbiology 68 Pages: 5387-5393
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] クリプトスポリジウムと水処理 (2002)
  • Author(s): 平田強, 森田重光, 橋本温
  • Journal Title: 用水と廃水 44 Pages: 304-312
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Development of new membrane filtration technology designed for removing Cryptosporidium parvum oocysts from at a least trans-membrane pressure (2002)
  • Author(s): Hirata, T., Morita, S., Takizawa, H., Jinbo, Y., Komatsu, K.
  • Journal Title: Proceedings of IWA World Water Congress and Exhibition (CD-R)
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Efficacy of low-pressure ultraviolet irradiation for inactivating Cryptosporidium parvum oocysts in turbid water (2002)
  • Author(s): Hirata, T., Morita, S., Sugimoto, H., Takizawa, H., Endo, T.
  • Journal Title: Proceedings of International Ultraviolet Association 1^<st> Asia Regional Conference on Ultraviolet Technologies (CD-R)
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Effect of ultraviolet irradiation on infectivity of Cryptosporidium parvum oocysts. (2002)
  • Author(s): Morita, S., Namikoshi, A., Hirata, T., Oguma, K., Katayama, H., Ohgaki, S., Motoyama, N., Fijiwara, M.
  • Journal Title: Applied and Environmental Microbiology 68, 11 Pages: 5387-5393
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Cryptosporidium and water treatment (2002)
  • Author(s): Hirata, T., Morita, S., Hashimoto, A.
  • Journal Title: Yousui to Haisui 44 Pages: 304-312
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Development of new membrane filtration technology designed for removing Cryptosporidium parvum oocysts from at a least trans-membrane pressure. (2002)
  • Author(s): Hirata, T., Morita, S., Takizawa, H., Jinbo, Y., Komatsu, K.
  • Journal Title: Proceedings of IWA World Water Congress and Exhibition (CD-R)
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Efficacy of low-pressure ultraviolet irradiation for inactivating Cryptosporidium parvum oocysts in turbid water. (2002)
  • Author(s): Hirata, T., Morita, S., Sugimoto, H., Takizawa, H., Endo, T.
  • Journal Title: Proceedings of International Ultraviolet Association 1^<st> Asia Regional Conference on Ultraviolet Technologies (CD-R)
  • Description: 「研究成果報告書概要(欧文)」より
• [Book] 紫外線消毒-水の消毒技術としての適用性 (2005)
  • Author(s): 平田強, 森田重光 他
  • Publisher: 技報堂出版
• [Book] 水系感染症リスクのアセスメントとマネジメント (2003)
  • Author(s): 金子光美, 平田強 監訳
  • Total Pages: 434
  • Publisher: 技報堂出版
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Morita S., et al.: "Efficacy of UV irradiation in inactivating Cryptosporidium parvum oocysts"Applied and Environmental Microbiology. Nov.. 5387-5393 (2002)