The influence of temperature on the infectivity of Fasciola hepatica miracidia to Lymnaea truncatula.

Experiments were performed to study the effect of water temperature on the host-finding capacity (snail localization, attachment, and penetration) of Fasciola hepatica miracidia. Specimens of Lymnaea truncatula were exposed to miracidia labeled in vivo with radioselenium, and the radioactivity which subsequently was confined to the snails was taken as a measure of the host-finding capacity of the parasite. The minimum temperature required for host-finding was 5 to 6 C and the optimum temperature was in the range between 15 and 26 C. The lack of host-finding capacity below 5 to 6 C could be reversed experimentally by raising the temperature. A clear inverse relationship was demonstrated between the environnd 24 C the host-finding capacity ceased after 24 to 30, 20 to 24, and 13 to 20 hr, respectively.