Which life stage is involved in the infection of pigs by Macracanthorhynchus hirudinaceus?

The involvement of the cystacanth stage in the lifecycle of Macracanthorhynchus hirudinaceus is critical for the infection of pigs. The adult worms reside in the intestines of pigs and produce eggs that are excreted in their feces. These eggs can then be ingested by an intermediary host, commonly a beetle. Inside the beetle, the eggs develop into the cystacanth stage, which is an infective larval form. When pigs consume these infected beetles, they ingest the cystacanths, leading to their subsequent development into adult worms within the pig's intestines.

Understanding this lifecycle highlights the importance of intermediate hosts in the transmission and infection process of certain parasites, including Macracanthorhynchus hirudinaceus. Therefore, recognizing the cystacanth stage in beetles as the point of infection for pigs is essential in the context of managing and preventing parasitic infections in swine.