Opisthorchis [oʺpis-thorʹkis]

From the Greek opisthen (behind) and orchis (testicle), Opisthorchis is a genus of trematode flatworms whose testes are located in the posterior end of the body. Rivolta is generally credited with discovering the first opisthorchid, which he named Distoma felineus, in a cat in Italy in 1884. However, the fluke may have been mentioned by Rudolphi in 1819, and in 1831, Gurlt published a textbook that included a drawing of a fluke that was almost certainly Opisthorchis. By the end of the 19th century, Distoma contained so many species that Blanchard introduced the genus Opisthorchis for elongated flat flukes with testes in the posterior end of the body. He chose Rivolta’s Opisthorchis felineus as the type species.