A field study of natural infections in three freshwater snails with Fasciola hepatica and/or Paramphistomum daubneyi in central France

Natural infections of three freshwater snails with Fasciola hepatica and/or Paramphistomum daubneyi were studied during two periods in 1996 and 1997 (June-July and September-October) on 18 farms located in the departments of Vienne and Haute Vienne (central France), and known for low prevalences of F. hepatica infections in ruminants. A total of 1573 Lymnaea glabra and 1421 L. truncatula 6 mm high or more were collected in the meadows of 13 farms and dissected under laboratory conditions. Snails with single or concurrent infections of F. hepatica and/or P. daubneyi were found for each Lymnaea species. InL. truncatula, global prevalences of natural infections with F. hepatica (3.8% in June-July, and 3.6% in September-October) were significantly greater than those recorded for P. daubneyi (1.1% and 0.8%, respectively). In L. glabra, global prevalences of F. hepatica infections (0.4% in each investigation period) were significantly lower than those found in L. truncatula, whereas there were no significant differences between prevalences of P. daubneyi infections. A total of 2721 Planorbis leucostoma measuring at least 4 mm in diameter were collected in the meadows of the other five farms on which L. truncatula was absent. In these planorbids, global prevalences of natural infections with F. hepatica were 0.4% in each period of investigation. Contrary to fasciolosis, snail infections with P. daubneyi were not noted on all farms of the Vienne and Haute-Vienne departments. Natural single or concurrent infections with F. hepatica and/or P. daubneyi in L. glabra and a natural infection of P. leucostoma with F. hepatica were found in swampy meadows on acid soil.