Infection of Lymnaea truncatula and Lymnaea glabra by Fasciola hepatica and Paramphistomum daubneyi in farms of central France

Natural infection of Lymnaea glabra and Lymnaea truncatula by Fasciola hepa tica and/or Paramphistomum daubneyi was studied at two periods of risk (Jun e-July and September-October) in 11 French farms known for their high preva lences of F. hepatica infection in ruminants. A total of 1778 L. truncatula and 2396 L. glabra measuring 6 mm or more in height were collected to dete rmine the prevalence of natural infection with F. hepatica and P. daubneyi. The role of four factors, i.e. season, snail co-infection (F. hepatica-P. daubneyi), ruminant host and the existence of single or mixed intermediate host communities, was investigated. There were no differences in prevalence s between the two risk periods. Go-infections in L, glabra were more freque nt than expected. The prevalences of infection with F. hepatica or P. daubn eyi in L, glabra were higher in farms rearing sheep than in farms rearing c attle. A similar finding was also noted for L. truncatula infected with P. daubneyi only. L. glabra was a much better intermediate host for F. hepatic a and P. daubneyi when it was the only available snail, possibly indicating an adaptation of parasites to their less usual host in local conditions. T he two trematodes preferably developed in L. truncatula rather than in L. g labra when both host species lived in the same places. (C) Inra/Elsevier, P aris.