Gastrodiscoides hominis is a trematode which belongs to the Paramphistomatidae family. It affects the colon of suids, rats, piscivore animals and primates (Strait et al, 2012).

Epidemiology

Gastrodiscoides hominis can be found in tropical regions, like the Philippines, Japan, Viet-Nam, Java islands, India, and Egypt. It has been reported in Old World Monkeys, namely macaques (Macaca spp.). Moreover, gastrodiscoidosis is the most frequent trematodosis in Old-World Primates (Strait et al, 2012).

Description

Gastrodiscoides hominis eggs are operculated and large (130-140 µm long and 80-85 µm large). Their content is granulomatous (Garcia, 2021).

Differential diagnosis

Differential diagnosis includes other trematode eggs of non-human primates, namely Fasciolopsis buski and Fasciola hepatica, as well as mite eggs. Differentiation between trematode eggs requires larva visualization after coproculture (Garcia, 2021). Mite eggs are of similar dimensions as trematode eggs. They are easy to identify when mature as embryos are clearly visible. However, differentiation is more difficult when the egg is immature (Petithory et al., 1995).

Clinical significance

Infection by Gastrodiscoides hominis is normally asymptomatic. In case of important parasite load, mucoid diarrhea and chronic colitis can appear (Strait et al, 2012).

Prophylaxis and treatment

In primates, Gastrodiscoides hominis infection can be treated successfully with praziquantel (40 mg/kg) (Johnson-Delaney, 2009). In humans, thymol, tetrachloromethane and tetrachloroethylene (Mas-Coma & Valero, 2006) and mebendazole (Dada-Adegbola et al, 2004) are efficient to treat Gastrodiscoides hominis infections.

Zoonotic transmission of this parasite does not occur in zoological park, as human contamination requires the ingestion of fresh aquatic plants on which the metacercarial forms of the parasite reside.