The effect of cyclic temperatures on the growth of Fasciola hepatica and Lymnaea viatrix

The experiment aimed to measure the effect of constant and variable tempera tures on the growth of Lymnaea viatrix snails, on the development of a Peru vian isolate of Fasciola hepatica eggs and on the development off: hepatica in the snails. This was carried out by cultivating infected and uninfected snails and fluke eggs in artificial, temperature controlled chambers. L. v iatrix snails were found to develop at a rate dependent on environmental te mperature, but developed at least as well under conditions of varying tempe rature as at the same mean constant temperature. F: hepatica eggs held at c onstant or varying temperatures, developed at a rate comparable to other re ports. However, eggs developing at varying temperatures appeared to have re duced hatchability. Parasite development within the snails was slow, though within the limits calculated fr-om the literature, and varying temperature did not appear to reduce development compared to constant temperatures.