Pork Tapeworm

***Taenia solium*** is the **pork tapeworm** belonging to cyclophyllid cestodes in the family Taeniidae. It is an intestinal zoonotic parasite found throughout the world, and is most prevalent in countries where pork is eaten. The adult worm is found in humans and has a flat, ribbon-like body, which is white in color and measures 2 to 3 m in length. Its distinct head, the scolex, contains suckers and a rostellum as organs of attachment. The main body, the strobila, consists of a chain of segments known as proglottids. Each proglottid is a complete reproductive unit; hence, the tapeworm is a hermaphrodite. It completes its life cycle in humans as the definitive host and pigsas intermediate host. It is transmitted to pigs through human feces or contaminated fodder, and to humans through uncooked or undercooked pork. Pigs ingest embryonated eggs called morula, which develop into larvae, the oncospheres, and ultimately into infective larvae, cysticerci. A cysticercus grows into an adult worm in human small intestines. Infection is generally harmless and asymptomatic. However, accidental infection in humans by the larval stage causes cysticercosis. The most severe form is neurocysticercosis, which affects the brain and is a major cause of epilepsy.

Human infection is diagnosed by the parasite eggs in the faeces. For complicated cysticercosis, imaging techniques such as computed tomography and nuclear magnetic resonance are employed. Blood samples can also be tested using antibody reaction of enzyme-linked immunosorbent assay. Broad-spectrum anthelminticssuch as praziquantel and albendazole are the most effective medications.

## Description

Adult *T. solium* is a triploblastic acoelomate, having no body cavity. It is normally 2 to 3 m in length, but can become much larger, sometimes over 8 m long. It is white in colour and flattened into a ribbon-like body. The anterior end is a knob-like head called a scolex, which is 1 mm in diameter. The scolex bears four radially arranged suckers (acetabula) that surround the rostellum. These are the organs of attachment to the intestinal wall of the host. The rostellum is armed with two rows of spiny hooks, which are chitinous in nature. The 22 to 32 rotelllar hooks can be differentiated into short (130-µm) and long (180-µm) types. The elongated body is called the strobila, which is connected to the scolex through a short neck. The entire body is covered by a special covering called tegument, which is an absorptive layer consisting of a mat of minute hair-like microtriches. The strobila is divided into segments called proglottids, 800 to 900 in number. Body growth starts from the neck region, so the oldest proglottids are at the posterior end. Thus, the three distinct proglottids are immature proglottids towards the neck, mature proglottids in the middle, and gravid proglottids at the posterior end. A monoecious species, each mature proglottid contains a set of male and female reproductive systems. The numerous testes and a bilobed ovary open into a common genital pore. The oldest gravid proglottids are full of fertilised eggs.

The infective larvae, cysticerci, in humans, have three morphologically distinct types. The common one is the ordinary "cellulose" cysticercus, which has a fluid-filled bladder 0.5 to 1.5 cm in length and an invaginated scolex. The intermediate form has a scolex, while the "racemose" has no evident scolex, but is believed to be larger and much more dangerous. They are 20 cm in length and have 60 ml of fluid, and 13% of patients can have all three types in the brain.

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