Changes in human fasciolosis in a temperate area: about some observations over a 28-year period in central France.

A retrospective study of 616 patients affected by fasciolosis was carried out to determine the numerical fluctuations of this disease over time, the recruitment of patients, and the modes of infection in a cattle-rearing area under a temperate climate (region of Limousin, central France). The annual number of patients showed irregular fluctuations between 1955 and 1987, after which it showed subsequent decreases until 1998. Before 1980, 66.3% of the persons under study were living in villages, whereas the others inhabited larger towns. An inverse relationship was noted after 1981: 80.8% of the individuals lived in towns consisting of > 1,000 inhabitants, whereas only 19.2% resided in smaller villages. Watercress was the infection mode in 98% of persons, with infections being attributed to four watercress species before 1980 versus only two species of Nasturtium sp. after 1981. The 235 watercress beds investigated in this study were found to contain 1 or 2 Lymnaea species as follows: L. truncatula only (84% of watering places), L. glabra only (6.3%), and both species (6.3%). In the populations of L. truncatula, natural infections of snails with Fasciola hepatica were irregular and occurred up to six times over the 28-year period in the region of Limousin. According to the authors, the decrease in human cases and the changes in the recruitment of patients might be explained by the demographic movements that occurred over several decades in the region of Limousin, with the moving of younger age groups into towns.