Gastrodiscoidiasis, a plant-borne zoonotic disease caused by the intestinal amphistome fluke Gastrodiscoides hominis (Trematoda: Gastrodiscidae)

Gastrodiscoidiasis is an intestinal trematodiasis caused by the only common amphistome of man Gastrodiscoides hominis and transmitted by small freshwater snails of the species Helicorbis coenosus, belonging to the family Planorbidae. Human and animal contamination can take place when swallowing encysted metacercariae, by ingestion of vegetation (aquatic plants) or animal products, such as raw or undercooked crustaceans (crayfish), squid, molluscs, or amphibians (frogs, tadpoles). Pigs appear to be the main animal reservoir of any significance in most endemic areas. Its geographical distribution covers India (including Assam, Bengal, Bihar, Uttar Pradesh, Madhya Pradesh and Orissa), Pakistan, Burma, Thailand, Vietnam, Philippines, China, Kazakstan and Volga Delta in Russia, and has also been reported in African countries such as Zambia and Nigeria. The presence of G. hominis in Africa needs further studies, to confirm that the African amphistome in question is really that species and not a closely related African species, and to ascertain its geographical distribution in this continent. In man, this amphistome fluke causes inflammation of the mucosa of caecum and ascending colon with attendant symptoms of diarrhoea. This infection causes ill health in a large number of persons, and deaths among untreated patients, especially children. Human infection by G. hominis is easily recognisable by finding the characteristic eggs of this amphistome in faeces. Although comparative assays about the efficacy of different drugs against this amphistome are lacking, there is nothing impeding to suggest Praziquantel as the drug of choice for this trematodiasis. Control methods should include (i) prevention of human contamination, (ii) actions at human level to cut disease dissemination by humans, (iii) control the disease at animal reservoir level, and (iv) actions at the level of the intermediate molluscan host.