Influence of shell size ofLymnaea columellaon infectivity and development ofFasciola hepatica

Abstract

AbstractExperimental infections ofLymnaea columellawithFasciola hepaticawere carried out to determine the influence of shell size on the infection rate and on the outcome of rediae and cercariae. Snails were divided into seven groups according to shell size: 2–4 mm, 5–6 mm, 7–8 mm, 9–10 mm, 11–12 mm, 13–14 mm and 15 mm or more. One hundred snails in each group were infected by using four miracidia for each snail. Snails with larger shell size showed a lower infection rate, the groups presenting the highest (79%) and lowest (2%) proportions of positives being those of 5–6 mm and 15 mm or more, respectively. Cercariae were present in 21% of them at 31 days post-infection, and cercarial shedding was observed 61 days post-infection. It was concluded that there is a non-linear negative association between shell size and infection rate.