metaceraria

A metaceraria is a type of larval stage in the life cycle of certain trematode (flatworm) parasites, which include flukes and liver flukes. The term "metaceraria" specifically refers to the infective stage of the parasite that is released from the first intermediate host and is capable of infecting the definitive host. This stage is characterized by its ability to penetrate and establish within the tissues of the definitive host.

The life cycle of trematodes typically involves two intermediate hosts and one definitive host. The metaceraria is released from the first intermediate host, such as a snail, and then seeks out and infects the second intermediate host, often a crustacean or fish. Once the metaceraria has established in the second intermediate host, it undergoes further development into the cercaria stage, which is then capable of infecting the definitive host.

The definitive host, usually a mammal or bird, ingests the infected second intermediate host, and the cercariae penetrate the intestinal wall, developing into adult worms. The adult worms then reproduce sexually, producing eggs that are excreted in the host's feces. These eggs can then hatch into miracidia, which infect the first intermediate host, completing the life cycle.

Metacerariae are significant in the context of human and animal health, as they can cause various diseases, including schistosomiasis, fascioliasis, and clonorchiasis. Control and prevention of these diseases often involve strategies to disrupt the life cycle at the metaceraria stage, such as controlling the populations of intermediate hosts.