Pseudosuccinea columella: experimental co-infections of juvenile and pre-adult snails with the digeneans Calicophoron daubneyi and Fasciola hepatica.

Abstract

Experimental co-infections of juvenile and pre-adult Pseudosuccinea columella with Calicophoron daubneyi and Fasciola hepatica (five miracidia of each digenean per snail) were carried out to determine the aptitude of this lymnaeid to ensure complete larval development of the former parasite, the latter or both. Snails infected with F. hepatica were found in the two groups of juveniles, i.e. 1 and 2mm at exposure, and the four groups of pre-adults, i.e. 3-6mm. The highest frequency of F. hepatica, i.e. 37.3%, was noted in the 4mm group. Low frequencies were noted for C. daubneyi and co-infections of both digeneans in the 3, 4 and 5mm groups. Two other groups of P. columella, measuring 3 and 4mm at exposure, were also constituted to study the characteristics of these co-infections. Compared to controls infected only with F. hepatica, the frequency of this digenean infection and the mean number of metacercariae were significantly lower in co-infected snails, while the patent period was significantly shorter. In snails harbouring C. daubneyi only or both digeneans, lower values were noted for prevalence, the patent period and the number of metacercariae. Pre-adult P. columella (3-5mm in shell height at exposure) were able to sustain larval development of C. daubneyi if they were co-infected with the sequence C. daubneyi +F. hepatica. Low values noted for the prevalence of C. daubneyi infection and the number of metacercariae would be in favour of a still incomplete adaptation between the snail population and the miracidial isolate.