Experimental Infection of Isospora Hominis in Man

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  • Parasitology Laboratory (Prof. M. Koidzumi), Keio-Gijuku University Medical School, Tokyo, Japan


  1. 1.Six cases of Isospora infection in man have been found in Japan since 1939. Four of them were infected in Japan and the remaining two in China.
  2. 2.Experimental human infection with this parasite was carried on in two volunteers. The symptoms and the courses of infection were quite similar in both cases.
  3. 3.Symptoms were as follows: diarrhoea, abdominal tenderness and distention, nausea, poor appetite, headache and fever.
  4. 4.Fever and diarrhoea began one week after the infection and continued about 10 days. Oocysts appeared in the stool 10 days after the infection and were discharged for a period of more than a month.
  5. 5.Without any treatment, symptoms subsided and the parasite disappeared. That is to say, the life cycle of human Isospora appeared to be self-limited.
  6. 6.A second experimental infection on one volunteer, carried on 33 days after the disappearance of oocysts of the first infection, was not successful.