TAENIA

Taenia is a genus of tapeworm that includes some important parasites of livestock. Members of the genus are responsible for taeniasis and cysticercosis in humans. There are more than 100 species recorded. They are morphologically characterized by a ribbon-like body composed of a series of segments called proglottids; hence the name Taenia (Greek tainia meaning ribbon, bandage or stripe). The anterior end of the body is the scolex. Not all members of the genus Taenia have an armed scolex (hooks and/or spines located in the "head" region), for example, Taenia saginata has an unarmed scolex, while Taenia solium has an armed scolex.  Proglottids have central ovary, with a vitellarium (yolk gland) posterior to it. As in all cyclophyllid cestodes, there is genital pore on the side of the proglottid. Eggs are released when proglottid deteriorates, and so a uterine pore is unnecessary.

SELECTED SPECIES

Taenia asiatica  Asian Taenia. Humans as definitive hosts, pigs and rarely cattle, as intermediate hosts. Taenia crassiceps Taenia gonyamai, parasite of antelope (larval-) and lions (adult forms). Taenia mustelae, which infects small carnivorans. Taenia pisiformis, which is common in wild dogs and in rabbits, who serve as intermediate hosts. Taenia rileyi, which infects bobcats. Taenia saginata  beef tapeworm. Infects cattle and humans, and can only reproduce while in the human gut. Taenia solium  Pork Tapeworm. Like T. saginata humans serve as its primary host, and it can only reproduce by the dispersal of proglottids while in the gut. These reinfect pigs when human faeces is improperly disposed of. This infection is most common in parts of Africa. Taenia taeniaeformis, which uses rodents as intermediate hosts and then inhabits cats as the definitive host.

LIFE CYCLE

The life cycle begins with either the eggs or the gravid proglottids being passed in the feces, which can last for days to months in the environment (1). Then, cattle or pigs ingest the contaminated vegetation with eggs or proglottids (2). The oncospheres hatch in the small intestine of the cattle or pig (3) and invade the intestinal wall to travel to the striated muscles to develop into cysticerci. Humans can become infected when eating raw beef or pork meat (4). In the human, the cysticercus develop into adults in two months in the intestines. Using their scolex, they attach to the small intestine (5) where they reside(6). Taenia saginata are about 1,000-2,000 proglottids long with each gravid proglottid containing 100,000 eggs, while Taenia solium contain about 1,000 proglottids with each gravid proglottid containing 50,000 eggs.

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