Minor Risk to Contract Metazoan Parasites via the Consumption of Edible Snails, Born and Reared in France

In a context of food security of animal consumption and diversification of protein sources, we have studied the risks to contract metazoan parasites through the consumption of 'gros-gris' snails (Cornu aspersum maximum) sampled in 12 French farms. The dissection of 361 adult snails, born and reared in France, revealed a very low parasite prevalence of 0.55% [Confidence interval: 0.15%-2.00%]. Each of the two parasitized snails harboured a single larva of the trematode Brachylaima at the metacercarial stage in its kidney. For its development, Brachylaima requires the presence of both terrestrial gastropods (first and second intermediate hosts) and vertebrates (definitive hosts) such as rodents and birds which faeces contain parasite' eggs. As for these vertebrate hosts, humans can be infected through the ingestion of parasitized snails and then harboured the parasite at an adult stage in the intestine, which could lead to digestive pathology. Our preliminary results suggest however very limited parasitological risks of the consumption of snails if they are born and reared in France, contrarily to wild snails from the subspecies C. aspersum aspersum ('petit-gris'), frequently found infected not only by Brachylaima, but also by nematodes and mites. In order to avoid snail contamination in helicicultures as much as possible, we recommend preventing intrusion of vertebrates, potentially parasitized, in the parks.