The relationship between the density of Fasciola hepatica miracidia and the net rate of miracidial infections in Lymnaea truncatula.

Experimental studies on the dynamics of infection of Lymnaea truncatula by the miracidia of Fasciola hepatica show that there is a linear relationship between the net rate of attachment of miracidia to snail epithelium and the density of infective stages. The probability of a snail remaining uninfected after exposure to a single miracidium varies with the size class of the snail. Under the conditions of the experiment (temperature, 15 degrees C; exposure period, 30 min; water volume, 8 ml), the probability was 0.46-0.48, 0.27-0.26 and 0.13-0.19 for snail size classes, 0.5-2.9, 3.0-5.9 and 6.0-8.9 mm respectively.