Paramphistomum daubneyi and Fasciola hepatica : influence of temperature changes on the shedding of cercariae from dually infected Lymnaea truncatula

Abstract

Dual infections of Lymnaea truncatula with Paramphistomum daubneyi and Fasciola hepatica were performed to determine whether temperature changes in snails (daily water change with spring water at 6 degrees-8 degrees C, which subsequently increased to room temperature at 20 degrees C) would influence snail infection and the production of cercariae by both trematodes. At day 30 post-exposure the surviving snails were individually placed in petri dishes to constitute two groups. Snails from the first group were maintained at a temperature of 20 degrees C, and the water in the petri dishes was changed daily. The protocol was identical for the second group of snails except that the water temperature was 6 degrees-8 degrees C when changed. The interval between exposure and the first shedding of cercariae in snails immersed in cold water for a short period was longer (67-69 days instead of 48-50 days in the 20 degrees C group). In both groups, snails infected only with F. hepatica or P. daubneyi or with both trematodes were detected. In snails infected only with F. hepatica the frequency of cercaria-shedding snails and the total number of metacercariae were significantly greater in the 20 degrees C group. Inversely, in snails infected only with P. daubneyi the frequency of cercaria-shedding snails and the number of metacercariae were significantly greater in the 6 degrees-8 degrees C group. In snails harboring both trematode larval forms, no significant difference in the frequencies of cercaria-shedding snails between the two groups was noted. Metacercariae of both trematodes were obtained from these snails. In the 20 degrees C group, F. hepatica metacercariae were more numerous, whereas in the 6 degrees-8 degrees C group the number of P. daubneyi metacercariae was greater. From these results it appears that greater activity of P. daubneyi cercariae occurs in snails subjected to daily temperature changes (from 6 degrees to 20 degrees C).

Natural prevalence in Cuban populations of the lymnaeid snail Galba cubensis infected with the liver fluke Fasciola hepatica: small values do matter

“…Indeed, in G. truncatula, the higher success is obtained when the molluscs are 4 weeks old (Rondelaud et al 2009b). Moreover, well-fed G. truncatula are less susceptible to infection and exhibit a higher redial production than starved snails (Kendall 1949;Kendall and Ollerenshaw 1963;Abrous et al 1999). Stress induced by pollution can also increase the risks of infection .…”

Natural light influences cercarial emergence of Calicophoron daubneyi but not that of Haplometra cylindracea from temperature-challenged Galba truncatula

“…However, another hypothesis based on an adaptation of F. hepatica and/or C. daubneyi cercariae to exit from the snail under the same environmental factors (the thermal shock and natural light in this case) cannot be excluded. An argument supporting this last assumption was the occurrence of mixed cercarial emergence in G. truncatula co-infected with C. daubneyi and F. hepatica when the snails contained live larval forms of both digeneans (Augot et al 1996;Abrous et al 1999b). …”

Prevalence of Trematode Larval Infections in Some Red Sea Snails

“…It may also affect cercarial shedding (the release of cercariae from the host snail in nature). However, the influence of environmental elements on cercarial shedding is trematode-specific (Abrous et al 1999).…”