Lymnaea glabra: progressive increase in susceptibility toFasciola hepaticathrough successive generations of experimentally infected snails

Abstract

Experimental infections of Lymnaea glabra (two populations) with Fasciola hepatica were carried out during seven successive snail generations, to determine if prevalence and intensity of snail infection increased over time through descendants of snails already infected with F. hepatica. Controls were descendants coming from uninfected parents and infected according to the same protocol. No larval forms were found in the bodies of control snails coming from uninfected parents. In contrast, prevalence and intensity of F. hepatica infection in snails originating from infected parents progressively increased from the F2 or F3 to the F6 generation of L. glabra. In another experiment carried out with the F7 generations of L. glabra and a single generation of Galba truncatula (as controls), the prevalence of F. hepatica infection and the total number of cercariae were lower in L. glabra (without significant differences between both populations). If the number of cercariae shed by infected snails was compared to overall cercarial production noted in snails containing cercariae but dying without emission, the percentage was greater in G. truncatula (69% instead of 52-54% in L. glabra). Even if most characteristics of F. hepatica infection were lower in L. glabra, prevalence and intensity of parasite infection increased with snail generation when tested snails came from infected parents. This mode of snail infection with F. hepatica suggests an explanation for cases of fasciolosis occurring in cattle-breeding farms where paramphistomosis is lacking and G. truncatula is absent.

The prevalence and development of digenean parasites within their intermediate snail host, Galba truncatula , in a geographic area where the presence of Calicophoron daubneyi has recently been confirmed

“…As a preferential selfer, G. truncatula snails have a high genetic differentiation between populations (Trouvé et al, 2003), a trait which could explain why G. truncatula susceptibility to F. hepatica can vary significantly between populations, with snails sourced from habitats devoid of natural contact with livestock shown to be more resistant to F. hepatica infection and its subsequent development (Rondelaud, 1993). The latter finding may be caused by incomplete adaptation between snail and parasite due to lack of contact (Rondelaud, 1993, Vignoles et al, 2002, Dreyfuss et al, 2012), with digenean/snail adaptation processes reliant on persistent contact (Boray, 1966, Rondelaud et al, 2014, Rondelaud et al, 2015). It remains unclear whether C. daubneyi is a new parasite in the UK, or has been present in the country at undetectable levels prior to its recent apparent emergence (Jones et al, 2017).…”

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

“…[19] for two populations of L. glabra infected with F. hepatica and raised according to the same protocol. In the three lymnaeids, prevalence of infection significantly increased with increasing generation of snails, even if the speed of this process over time varied with each lymnaeid species or each population in the case of L. glabra .…”

Insights into the reproductive activity ofOmphiscola (Lymnaea) glabra(Gastropoda: Lymnaeidae) in relation to soil geology in Central France

“…Mu¨ller) is a natural snail host of the parasite Fasciola hepatica (Linnaeus). Three modes of snail infection were demonstrated for this lymnaeid: (i) the infection of juveniles measuring less than 2 mm in shell height at miracidial exposure (Kendall, 1950;Busson et al, 1982), (ii) the co-infection of juveniles and pre-adults (3-6 mm in shell height) with F. hepatica and another digenean, Calicophoron daubneyi (Dinnik) and (iii) the infection of pre-adults, coming from F. hepatica-infected parents, over several snail generations (Rondelaud et al, 2015). Among these three modes, the co-infection of O. glabra with C. daubneyi and F. hepatica was the most frequent (Abrous et al, 1999(Abrous et al, , 2000.…”

“…Among these three modes, the co-infection of O. glabra with C. daubneyi and F. hepatica was the most frequent (Abrous et al, 1999(Abrous et al, , 2000. The other two modes were of minor importance and were noted only in limited cases (Rondelaud, 1980;Rondelaud et al, 2015).…”