Trichobilharzia regenti is a nasal parasite of bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s that causes cercarial dermatitis in humans.

Life cycle

The life cycle for avian schistosomes is similar to that of human schistosomiasis. Adult flukes mate and produce eggs which are usually excreted with the bird's feces. Once in the water, the eggs hatch, liberating many miracidia

Miracidium

Trematodes are small parasitic flatworms that use vertebrates as their definitive host, and molluscs as their intermediate host. In order to accomplish this, they have several varied lifecyle stages....

. The miracidia, using their cilia, swim around eventually finding a molluscan intermediate host, usually a snail. In the snail, the miracidium develops into a sporocyst, which in turn develops into a daughter sporocyst or redia. Eventually, the sporocysts and rediae develop into cercariae. The cercariae exit the snail through feces and penetrate the skin of new avian hosts, migrating to blood vessels of the bird to mature into adults and complete the cycle. Humans become infected with cercarial dermatitis when they are exposed to the dermatitis-producing cercariae.