Trichobilharzia regenti

The life cycle of T. regenti is analogous to that of human schistosomes. Adult flukes mate in a nasal mucosa of anatid birds (e.g. Anas platyrhynchos, Spatula clypeata or Cairina moschata) and produce eggs with miracidia which hatch directly in the host tissue and leak outside when the bird is drinking/feeding. Once in water, the miracidia swim using their cilia and actively search for a proper molluscan intermediate host (Radix lagotis, Radix labiata, Radix peregra). In the snail, the miracidia develop into a primary sporocyst in which secondary sporocysts are formed and give rise to cercariae later on. Cercariae, infective larvae, exit the snail and penetrate the skin of an avian host. After penetration of the host's skin, they shed the immunogenic surface glycocalyx and transform to schistosomula (subadult stage, sg. schistosomulum). Schistosomula then look for peripheral nerves to use them to get to the spinal cord. Through it they continue their migration to the brain and, finally, the nasal tissue in a bill. Here, they mature, copulate and lay eggs while causing pathology (inflammatory infiltration, haemorrhages). If mammals are infected by cercariae (instead of birds), the parasites die in the skin being entrapped by immune response. The clinical manifestation of such infection is known as a neglected allergic disease called cercarial dermatitis (or swimmer's itch). …