Lack of molluscan host diversity and the transmission of an emerging parasitic disease in Bolivia

Fasciolosis is a re-emerging parasitic disease that affects an increasing n umber of people in developing countries. The most severe endemic affects th e Bolivian Altiplano, where the liver fluke (Fasciola hepatica) and its her maphroditic snail host, Lymnaea truncatula, have been introduced from Europ e. To achieve a better understanding of the epidemiological situation and t he consequences of the colonization event of this invasive species, genetic analysis of Bolivian snail populations was needed. Here we compare the gen etic diversity and population structure of snail samples from the Bolivian Altiplano with samples from the Old World at six polymorphic microsatellite loci. Whereas some variability exists in the snail populations from the Ol d World, we observe only a single genotype of L. truncatula in the Bolivian Altiplano. We discuss the possible explanations for such a reduction in ge netic variability, and, given the high natural parasitism pressures exerted on the snail populations, we discuss the relevance of this result for host -parasite interactions.