Helminth-Trematode: Dicrocoelium dendriticum

Abstract

Dicrocoeliosis is a rare foodborne zoonosis of the human biliary tract caused by Dicrocoelium dendriticum, commonly known as the ‘lancet fluke’ or ‘small liver fluke’. D. dendriticum is a small lanceolate trematode parasite that commonly infects the biliary tract of animals (mainly ruminants) and humans. The life cycle of this parasite is very complex since land molluscs and ants are required as first and second intermediate hosts, respectively. Infection occurs by passive ingestion of ants containing the infective stages (metacercariae), whereas pseudo-infections (presence of D. dendriticum eggs in stool in the absence of adult worms) are the consequence of eating raw or undercooked animal liver; in such a case eggs pass unchanged through the digestive tract of an uninfected patient. Dicrocoeliosis often remains clinically undetected or undiagnosed in human beings, most likely because of its subclinical nature. As with other foodborne trematode infections, diagnosis is often unsatisfactory when using the current copromicroscopic techniques and the use of new multivalent and highly sensitive copromicroscopic methods, e.g., the FLOTAC techniques, is advised. The importance of D. dendriticum is often forgotten in the food safety and hygiene community due to the rarity of human clinical cases of dicrocoeliosis. These few clinical cases, however, could represent only the tip of the iceberg. Nevertheless, since 2007, D. dendriticum has been included in the list of causative agents for which burden of disease estimates are to be derived according to the Foodborne Disease Burden Epidemiology Reference Group of the World Health Organization.