Volume 4, Issue 3
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



The observations presented indicate that the incidence of protozoan infections was lower on the floor of the Kofu Valley, Yamanashi Prefecture, Japan, where drinking water was obtainable from open wells, than in secondary valleys of surrounding mountains where the primary source of water was either a river or an irrigation stream. For the incidence tended to increase from upper to lower levels of the valley, in agreement with an expected increase in fecal pollution. Fluctuations in the incidence of and which were irrespective of valley levels, and a disproportionate increase in the rate of in the hill communities prompt the speculation that the several modes of protozoan transmission may not be equally effective for and the other amebas. Since cyst drying has been shown to be less damaging to and , the latter may be more dependent on water transmission. Although other factors such as direct and food handler transmission and flies may have contributed to the increased incidence of protozoa in hill villages, it is believed that water was the major factor of difference.


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