Lymnaea palustris and Lymnaea fuscus are potential but uncommon intermediate hosts of Fasciola hepatica in Sweden
Abstract
Background: Lymnaea palustris and L. fuscus are members of the European stagnicolines (Gastropoda: Lymnaeidae)Results: One field-collected L. palustris (out of n = 668) contained F. hepatica as determined by PCR. On the other hand, stagnicolines artificially exposed to F. hepatica miracidia resulted in successful infection with fully differentiated cercariae, but only in juvenile snails (size, 1-2 mm at exposure) and with a prevalence of 51% and 13% in L. palustris and L. fuscus, respectively.
In contrast, 90% of juvenile (size, 1-2 mm) and 92% of preadult G. truncatula (size, >= 2-4 mm), respectively, were successfully infected. Delayed, reduced and/or no spontaneous cercarial shedding was observed in the two stagnicolines when compared to G. truncatula.
However, at snail dissection most cercariae from L. fuscus and L. palustris were able to encyst similarly to those from G. truncatula. Conclusion: Both L. fuscus and L. palustris can sustain larval development of F. hepatica but with an apparent level of age resistance.
The finding of a single F. hepatica positive specimen of L. palustris, together with infection characteristics from the experimental infection, suggest that L. palustris is a more suitable snail vector of F. hepatica than L. fuscus. The reduced growth observed in both stagnicolines was contrary to the 'parasitic gigantism' theory.
Overall, it seems that the epidemiological role of L. palustris in transmission of F. hepatica in Sweden is likely to be much lower than for G. truncatula.