In the five communities of Urakawa, Sakuma-machi, Shizuoka Prefecture, we have taken measures to Prevent and exterminate ascaris infection, and at the same time studied the causes of infection chiefly from the point of view of environmental conditions. The percentages of ascaris egg-carriers showed a significant difference between 1) farmers and non-farmers; 2) families with and without night-soil; 3) amounts of detergent used for cleaning vegetables; 4) persons with and without experience of anthelmintic treatment.
The group of families that showed extremely high rate of positivity were the farmers not provided with night-soil stores, and the farmers provided with such stores showed about the same rate of positivity as non farmers a fact evidences the appreciatng effect of night-soil stores. On the other hand, the rate of positivity among familis that have no night-soil stores but are in the habit of cleaning vegetables with detergent showed no significant difference as compared with the families provided with night-soil storesa positive evidence of the good effect of detergent.