Treatment failure after multiple courses of triclabendazole in a Portuguese patient with fascioliasis

Fascioliasis is a trematode flatworm infection caused by Fasciola hepatica Humans are incidental hosts, and the infection is most often acquired by eating watercress grown in contaminated water in livestock-rearing areas. Triclabendazole is the only highly effective treatment, with a reported cure rate of >90%. Treatment failure may be due to several factors, though resistance is rare in humans and scarcely reported, most probably a reflection of the widespread use of anthelmintics in livestock. There are three papers describing cases of treatment failure, possibly due to resistance, in the Netherlands, Chile and Peru. We document for the first time one case of failure after multiple treatment courses with triclabendazole in Portugal, probably due to resistance to the anthelmintic. Our aim is to alert for the emergence of resistance across continents, with consequent predictable difficulties in the management of the disease and encourage more investigation in the field.