Taenia solium, better known as the pork tapeworm, is a parasite of humans that, upon infection, can result in cysts, blurred vision, blindness, headaches, seizures, hydrocephalus, and even death. It is common in developing countries, but has been observed in the United States as well.
How does it reproduse.
Taeniasis is a tapeworm (cestode) infection acquired by the
ingestion of raw orundercooked meat of infected animals.
Although many species exist, two species, Taenia saginata
and Taenia solium, cause pathology in humans. T. saginata
is associated with the ingestion of the worm's larval form
found in infected beef while T. solium is associated with that
of infected pork.
STEP 1. Infected humans (definitive host) excrete the eggs or gravid proglottids in their feces,passing the parasite from the gastrointestinal tract onto nearby vegetation. In egg or gravid proglottid form, T. solium is able to remain viable anywhere from days to months. T. solium can be diagnosed at this point in the life cycle.
Note: Autoinfection can also occur at this point in the life-cycle via fecal-oral contamination. In this case, eggs or gravid proglottids re-enter the body through themouth and often travel to the central nervous system (CNS), the muscles or the eye, where they develop into cysticerci. The presence of cysticerci in these locations leads to the pathogenesis of cysticercosis (neurocysticercosis in the CNS).(4-5)
STEP 2. Pigs (intermediate host) acquire infection by eating and digesting the eggs or gravid proglottids along with the parasitized vegetation.
STEP3. The eggs or gravid proglottids migrate to the pig's intestine and as oncospheres, break through the intestinal wall. Then, via the circulatory system, they embed themselves in the muscles of the pig and develop into cysticerci (the infective form of T. solium). Cysticerci have the ability to persist in the muscle for many years.
STEP 4. Humans acquire the infection by eating the undercooked orraw flesh of an infected animal.
STEP 5,6. Cystercerci migrate to the small intestine of the human host and develop into their adult tapeworm form normally within two months. By attaching to the intestinal wall with their scolices (hooked structures), these adult tapeworms may persist for long periods of time, even years.
Like all members of the Cestoda, T.solium lacks a digestive system,and feeds by absorbing nutrients (in the form of carbohydrates) from the digestive system of its host across its membrane. This requires T.solium to maximize its surface area: volume ratio. T. solium has adapted in several ways to accomplish this goal. The tapeworm has a flattened body, which maximizes the area available for nutrient absorption while minimizing the volume these nutrients musttravel to reach each of the organism’s cells. Cestodes also have microtriches, which are tiny projections that cover the entire body. These serve to increase the surface area even more.
T. solium has a very similar life cycle to Taenia saginata,. The Humans usually infect through eating infected pork, fostering adult tapeworms in the intestine, and passing eggs through feces, but autoinfectionis also possible. In that case, a cysticercus (a larva sometimes called a "bladder worm") develops in the human and the human acts like an intermediate host. This happens if eggs get to the stomach, usually as a result of contaminated hands, but also due to retroperistalsis. Cysticerci often occur in the central nervous system, which can cause major neurological problems like hydrocephalus,paraplegy, meningitis, convulsions and even death. The condition of having cysticerci in one's body is called cysticercosis.
Eggs can be diagnosed only to the family (biology) level, but if a proglottid's uterus is stained with India ink, the number of visible uterine branches can help identify the species: unlike the Taenia saginata uteri, T. solium uteri have only five to ten uterine branches on...
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