Paddy Field Dermatitis in Saitama Prefecture / 日本農村医学会雑誌

ABSTRACT

Knowledge of output of <I>Trichobilharzia brevis</I> cercariae from the snail host, <I>Austropeplea ollula</I> is important in the design of control measures of paddy field dermatitis because the level of human infection will be related to the number of freed cercariae which emerged from infected snails and the duration of the cercarial shedding period.<BR>To determine the number of cercariae emerging from a snail following exposure to a single miracidium, each of 33 snails was exposed for a 10-hour period to a miracidium of <I>T. brevis</I>. Thirteen of the exposed snails ultimately shed cercariae, which were counted at least once daily, usually at 10 a.m.<BR>The snails began to release cercariae from 24 to 35 days after exposure at temperatures ranging from 22 to 24°C. The average output per snail per day of snails examined varied from 68. 4 to 312. 3 the greatest daily output of a single snail was 911.<BR>The total output of a single snail varied from 3, 593 to 31, 091 the average for all 13 examined was 14, 159, with the cercarial shedding period ranging from 28 to 188 days.