2002 Fiscal Year Final Research Report Summary
Studies on the transmission modes of bovine neospora and its infectivity to humans
| Project/Area Number |
12556052
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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 | 展開研究 |
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| Research Field |
Applied veterinary science
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| Research Institution | Hokkaido University |
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Principal Investigator |
TAKASHI Umemura Graduate School of Veterinary Medicine, Professor, 大学院・獣医学研究科, 教授 (00151936)
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| Co-Investigator(Kenkyū-buntansha) |
HITOSHI Chiba School of Medicine, Medical Hospital, Assistant Professor, 医学部附属病院, 講師 (70197622)
AKINORI Shimada Faculty of Agriculture, Tottori University, Professor, 農学部, 教授 (20216055)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Neospopra caninum / neosporosis / bovine abortion / persistent infection / steroid hormones / transneural infection / zoonosis / vertical transmission |
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| Research Abstract |
We isolated the persistently infected tachyzoites of Neospora (N.) caninum from the brain of seropositive cow. The protozoa inoculated subcutaneously to female mice invaded the brain via hematogenerous route and persisted in situ. The persistently-infected protozoa reactivated at pregnancy and infected fetuses transplacentally.
Seropositive cows for N. caninum were widely and densely distributed among the farms in Hokkaido and most of them were infected transplacentally from their dams.
Four of 271 human serum samples collected at medical hospital had the antibody against N. caninum. Detailed examination on the positive cases revealed that those patients were immunized with N. caninum antigen but might not be infected with the protozoa.
Neospora caninum antigens recognized by lgG of mice were analyzed by western blot at various stages of infection. Forty-three kda antigen was consistently recognized by the infected host and this antigen was best recommended for the detection kit of N. caninum antibody.
Effects of three, pregnancy-related steroid hormones (progesterone, estrabiol-17β and corticosterone) on the reactivation of N. caninum were examined using mice and Vero cells infected with the protozoa.
Physiological levels of steroid hormones did not reactivated N. caninum in the brain of the mice and cell culture. Neospora caninum was injected in the eye balls and food pad of immunodeficient nude mice, immunocompetent mice and hyperimmunized mice. The protozoa propagated mainly via hematogeneous route in the nude mice, via both hematogeneous and transneural routes in immunocompetent mice, and via transneural route in hyperimmunized mice. This experiment was the first in which transneural propagation of protozoa was substantiated by the animal experiment.
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