Taenia asiatica

Taenia asiatica, commonly known as Asian taenia or Asian tapeworm, is a parasitic tapeworm of humans and pigs. It is one of the three species of Taenia infecting humans and causes taeniasis. Discovered only in 1980s from Taiwan and other East Asian countries as an unusual species, it is so notoriously similar to Taenia saginata, the beef tapeworm, that it was for a time regarded as a slightly different strain. But anomaly arose as the tapeworm is not of cattle origin, but of pigs. Morphological details also showed significant variations, such as presence of rostellar hooks, shorter body, and fewer body segments. The scientific name designated was then Asian T. saginata. But the taxonomic consensus turns out to be that it is a unique species. It was in 1993 that two Korean parasitologists, Keeseon S. Eom and Han Jong Rim, provided the biological bases for classifying it into a separate species. The use of mitochondrial genome sequence and molecular phylogeny in the late 2000s established the taxonomic status. T. asiatica causes intestinal taenisis in humans and cysticercosis in pigs. There is a suspicion that it may also cause cysticercosis in human. Like other taenids, humans are the definitive hosts, but in contrast, pigs, wild boars, as well as cattle can serve as intermediate hosts. Moreover, SCID mice and Mongolian gerbil can be experimentally infected. The life cycle is basically similar to those of other taenids. Humans contract the infection by eating raw or undercooked meat – a practice common in East and Southeast Asia – which is contaminated with the infective larva called cysticercus. Cysticercus develops into adult tapeworm in human intestine, from where it releases embryonated eggs along faeces into the external environment. Pigs acquire the eggs from vegetation. The eggs enter the digestive tract, which they penetrate to migrate to other body organs. Unlike other Taenia they preferentially settle in the liver, where they form cysticerci.