Adaptation of Lymnaea fuscus and Radix balthica to Fasciola hepatica through the experimental infection of several successive snail generations

Abstract

BackgroundHigh prevalence of Fasciola hepatica infection (>70%) was noted during several outbreaks before the 2000s in several French farms where Galba truncatula is lacking. Other lymnaeids such as Lymnaea fuscus, L. glabra and/or Radix balthica are living in meadows around these farms but only juvenile snails can sustain complete larval development of F. hepatica while older snails were resistant. The low prevalence of infection (<20%) and limited cercarial production (<50 cercariae per infected snail) noted with these juveniles could not explain the high values noted in these cattle herds. As paramphistomosis due to Calicophoron daubneyi was not still noted in these farms, the existence of another mode of infection was hypothesized. Experimental infection of several successive generations of L. glabra, originating from eggs laid by their parents already infected with this parasite resulted in a progressive increase in prevalence of snail infection and the number of shed cercariae. The aim of this paper was to determine if this mode of snail infection was specific to L. glabra, or it might occur in other lymnaeid species such as L. fuscus and R. balthica.MethodsFive successive generations of L. fuscus and R. balthica were subjected to individual bimiracidial infections in the laboratory. Resulting rediae and cercariae in the first four generations were counted after snail dissection at day 50 p.e. (20°C), while the dynamics of cercarial shedding was followed in the F5 generation.ResultsIn the first experiment, prevalence and intensity of F. hepatica infection in snails progressively increased from the F1 (R. balthica) or F2 (L. fuscus) generation. In the second experiment, the prevalence of F. hepatica infection and the number of shed cercariae were significantly lower in L. fuscus and R. balthica (without significant differences between both lymnaeids) than in G. truncatula.ConclusionThe F. hepatica infection of several successive snail generations, coming from parents infected with this parasite, resulted in a progressive increase in prevalence and intensity of snail infection. This may explain high prevalence of fasciolosis noted in several cattle-breeding farms when the common snail host of this digenean, G. truncatula, is lacking.

Confirmation of Galba truncatula as an intermediate host snail for Calicophoron daubneyi in Great Britain, with evidence of alternative snail species hosting Fasciola hepatica

“…Despite the difficulties recorded in experimental infections of Radix spp. with F. hepatica [ 18 ], studies have shown that snails infected at the juvenile stage [ 19 ] or persistently exposed to F. hepatica over successive generations, are more susceptible to infection and eventual shedding [ 20 ]. These results could also explain the F. hepatica -positive P. antipodarum recorded in our study, however, it must be stressed that these infected snails were not dissected, and thus no confirmation of the patency of infection can currently be made.…”

Pseudosuccinea columella: age resistance toCalicophoron daubneyiinfection in two snail populations

“…In spite of the age resistance of P. columella to C. daubneyi infection, this situation may not be stable over the following years and a change in the susceptibility of these populations to this digenean can be expected if miracidia are permanently present in the habitats where snails are living. An argument supporting this last assumption came from the two reports by Rondelaud et al [ 34 , 35 ]. Pre-adults (4 mm in height at exposure) of three lymnaeid species ( L. fuscus , L. glabra , Radix balthica Linnaeus, 1758 [ 24 ]) are known to be resistant to F. hepatica infection [ 9 , 19 , 28 ].…”

“…Pre-adults (4 mm in height at exposure) of three lymnaeid species ( L. fuscus , L. glabra , Radix balthica Linnaeus, 1758 [ 24 ]) are known to be resistant to F. hepatica infection [ 9 , 19 , 28 ]. In contrast, the F. hepatica infection of several successive generations of pre-adults, coming from parents already infected with this parasite, resulted in a progressive increase in prevalence and intensity of snail infection [ 34 , 35 ]. If in the future, P. columella colonizes French hydrographical networks up to open drainage systems, this lymnaeid might play an active role in C. daubneyi transmission and supplant the local common snail host, G. truncatula .…”

Intermediate hosts of Protostrongylus pulmonalis (Frölich, 1802) and P. oryctolagi Baboš, 1955 under natural conditions in France

“…This approach is, however, essential for understanding the development of the parasite life cycle, and thus to evaluate the risk of dispersion and contamination of the parasite in populations of definitive hosts. Our study aims to find these hosts in natura for different species of protostrongylids previously isolated from lungs of hares in France, in order to identify the host-parasite relationship and more precisely the gastropod-nematode relationship, by using techniques previously tested for Trematodes [ 64 - 66 ].…”