Land snails and periods at high risk for protostrongylid infection on a sheep-grazed pasture of Northeast Tunisia

Abstract

The population density and level of infection of terrestrial molluscs, and the output by sheep of first stage protostrongylid larvae, were assessed monthly during a 1-year study. Muellerius capillaris was the predominant protostrongylid (≈80% of the larval output); Neostrongylus was also found. Eobania vermiculata, Cernuella virgata and Trochoidea elegans were the most common molluscs. Juveniles were less infected than adults. Banded E. vermiculata had a lower intensity of infection than unbanded ones. Nearly 75% of protostrongylid larvae harboured by molluscs on the studied pasture were found in E. vermiculata. The infectivity of pasture was at its lowest in the dry and hot period (June–September). Infection of snails was primarily related to temperature and the importance and frequency of rains, and secondarily to larval excretion in sheep faeces.