M. Luzonpena et al., THE OVERWINTERING OF EGGS, INTRAMOLLUSCAL STAGES AND METACERCARIAE OFFASCIOLA-HEPATICA UNDER THE TEMPERATURES OF A MEDITERRANEAN AREA (MADRID, SPAIN), Veterinary parasitology, 55(1-2), 1994, pp. 143-148
The survival of embryonated and unembryonated eggs, of snails with mat
ure or immature infection and of metacercariae over the winter of a Me
diterranean area was analyzed. Embryonated eggs were more resistant th
an unembryonated eggs to cold weather, leaving a residual contaminatio
n which was responsible for earlier spring infection of the snail. Ove
rwintering was similar in snail populations with both mature and immat
ure infections although the lifespan was shorter in the former. Both s
nail populations survived in the mildest winter but not in the coldest
. Only metacercariae from mid autumn were able to overwinter in an sig
nificant proportion (45%) but they were non-viable by mid spring. Our
results suggest that in very cold winters no risk for grazing animals
should be expected in spring.