Effects of temperature and host density on the snail-finding capacity of cercariae of Echinostoma caproni (Digenea: Echinostomatidae)

The effect of temperature (19-36 degrees C) and snail host density (0.014-10 snails/l) on the snail-finding capacity of Echinostoma caproni cercariae is described. The initial swimming speed increased whereas the length of the infective period decreased with increasing temperature. The combined effect resulted in the E. caproni cercarial snail-finding capacity being temperature independent in the range 19 to 36 degrees C at a snail density of 0.014 snails/l. A moderate temperature dependency was, however, seen at a lower snail density. The cercarial snail-finding capacity was snail-host density dependent in the density range 0.014 to 1 snail/l. The findings from this study show that a relatively low and biologically realistic snail host density must be used in experimental studies if realistic estimates of the dynamics of cercarial transmission are to be obtained.