The influence of different food sources on cercarial production in Lymnaea truncatula experimentally infected with Digenea

Abstract

-Experimental infections of Lymnaea truncatula with a digenean species (Fasciola gigantica, F. hepatica, or Paramphistomum daubneyi) were performed under laboratory conditions to study the effect of four sources of food (microalgae, romaine lettuce, wheat germs, or modified Boray diet) on cercarial production. The mean number of F. hepatica, F. gigantica, or P. daubneyi cercariae was significantly greater when snail food was microalgae or Boray diet. The lowest cost prices for 100 metacercariae of F. hepatica (9.7-10.1 euros) were noted when algae of Boray diet were used as food for snails. In contrast, the highest prices (18.0-18.5 euros) were found in lettuce-reared snails. The choice of a source of food for breeding the intermediate hosts of F. hepatica and collecting metacercariae must take into account the importance of the commercial demand for metacercariae and will depend on the strategy the producer wishes to develop.breeding method / Fasciola hepatica / food / Lymnaea truncatula / Paramphistomum daubneyi Résumé -Influence de différentes sources de nourriture sur la production cercarienne chez des Lymnaea truncatula infestées expérimentalement par des Digènes. Des infestations expérimenta-les de Lymnaea truncatula avec un Digène (Fasciola gigantica, F. hepatica, or Paramphistomum daubneyi) ont été réalisées dans les conditions du laboratoire afin d'étudier l'impact de quatre types de nourriture (algues, laitue romaine, germes de blé, aliment modifié de Boray) sur la croissance des mollusques et la production cercarienne. La production cercarienne de F. hepatica, de F. gigantica ou de P. daubneyi était significativement plus élevée lorsque le mollusque était nourri avec des algues ou avec l'aliment modifié de Boray. Les prix de revient les plus faibles pour 100 métacercaires de F. hepatica (9,7-10,1 euros) ont été obtenus avec l'emploi d'algues ou de l'aliment modifié de Boray. Les 95 Vet. Res. 33 (2002) 95-100

Variability in the prevalence of infection and cercarial production in Galba truncatula raised on a high-quality diet

“…mainly agreed with those recorded by our team when they assessed experimental infections of local G. truncatula by local miracidia of F. hepatica (e.g. Rondelaud and Dreyfuss 1997;Rondelaud et al 2002) or of P. daubneyi (Abrous et al 1999). The absence of significant differences between the growth of cercariae-shedding snails or between their life-spans is more difficult to comment on.…”

“…Indeed, in the system Bulinus truncatus -Schistosoma haematobium, the raising of snails on a mixture of foods resulted in a better fitness in terms of snail survival and prevalence of infections (Ismail and Haroun 2001). In contrast, in two other snail-parasite models, snail mortality (Keas and Esch 1997;Rondelaud et al 2002) and the prevalence of infections (Rondelaud et al 2002) did not significantly differ among snail groups raised on a low-or a highquality diet. In contrast, little information is available on the lengths of the prepatent and patent periods in infected and well-fed snails, whatever the model studied by authors.…”

“…Kendall 1949;Boray 1969;Lee et al 1995;Keas and Esch 1997;Ismail and Haroun 2001;Rondelaud et al 2002) when snails were raised on a high-quality diet. However, in the present study, there was a variability in the intensity of cercarial shedding, as cercarial production from snails raised on lettuce+Tetraphyll was 1.9-11.3 times higher than that noted in groups raised on lettuce.…”

The presence of uninfected Omphiscola glabra in a breeding of infected Galba truncatula enhanced the characteristics of snail infections with Fasciola hepatica

“…The cost of commercial production of these larvae needs to be taken into account to propose the lowest sale price possible to researchers and/ or institutions. As the cost is closely dependent on the choice of a food source for breeding the intermediate hosts of F. hepatica (Rondelaud et al 2002), it is useful to reduce it by the selection of the best method to feed snails. Several sources of high-quality food have already been proposed by different authors (Kendall 1949(Kendall , 1965Boray 1969;Lee et al 1994;Rondelaud et al 2004) for Galba truncatula, as this amphibious snail is the most used lymnaeid in European countries for experimental infections with F. hepatica.…”

“…Several sources of high-quality food have already been proposed by different authors (Kendall 1949(Kendall , 1965Boray 1969;Lee et al 1994;Rondelaud et al 2004) for Galba truncatula, as this amphibious snail is the most used lymnaeid in European countries for experimental infections with F. hepatica. However, the use of these food sources often requires the presence of a technician, thus explaining the high cost of metacercariae (Rondelaud et al 2002).…”