Wednesday, March 14, 2012

Taenia solium: Its Eating Your Brain!

Taenia solium, more commonly know as the Pork Tapeworm, is a parasitic worm that uses humans and pigs (go figure) as its major hosts. [1] It is most commonly found in the warm climates regions of the world, and is very similar to Taenia saginata, the Beef Tapeworm. [2] We usually think of adult parasitic worms as tiny organisms with quick generation times, however T. solium can live to be up to a few years old and usually grow to be a dozen feet long. It is spread via human feces (i.e. the pig consumes the feces of the human beings containing the Pork Tapeworm eggs, where the worm eggs develop and move to the muscle tissue, to be ingested by humans). [2] When its larval stage is ingested by a human, it generally develops in their intestines and releases eggs into the feces. Sometimes situations differ, in which case the Pork Tape worm can cause an infection known as Cysticercosis (sis-tis-err-coh-sis), a severe tissue infection. This is one parasitic monster you don't want to mess with. [3]

Symbiont Description: 
Starting from domain and working towards genus, T. solium belongs to Eukarya, Animalia, Platyhelminthes, Cestoda, Cyclophyllidea, Taeniidae, and Taenia. Morphologically, the adult Pork Tapeworm is reminiscent of every other adult tapeworm--consisting of many proglottid segments and a scolex. [1] Each proglottid has a genital opening on one side and on its scolex are four suckers. Its cysticerci (larval form) differs in that the scolex is invaginated. Typically, humans are parasitized by the organism through ingestion of under-cooked pork, however, we have to capability for autoinfection. [2] In this situation, the entire life cycle of the Pork Tapeworm is contained within the human. Instead of the larval stage of the tapeworm migrating from a pig's intestines to its muscle tissue, the larva migrate from the human intestines to other parts of the body; most commonly the brain.

Host Description: 
Generally, the intermediate host is a domesticated pig. Because the pig is domesticated, it is in close contact with humans, the other species needed for completion of the full life cycle. The pig is able to ingest fecal matter of the humans containing the eggs of the Pork Tapeworm. The eggs hatch inside the pig and burrow through its intestinal wall, stopping in the pigs muscle tissue where they can then develop into larvae. [1]

Life Cycle:

The adult T. solium lays its eggs into human feces. When either the eggs or gravid (pregnant) proglottid segments inside the feces are consumed by a pig (or a human in the case of autoinfection), T. solium has reached its intermediate host. Here the Pork Tapeworm eggs will hatch within the pig's intestinal tract and migrate to its muscle tissue where it will develop into its larval stage, called cysticerci. When the pig is killed, processed, and eventually eaten by humans, the infected muscle tissue can further develop in the intestines of said humans (generally only when the meat is under-cooked). The T. solium use their scolex suckers to physically attach themselves to the walls of the intestines, where they can begin to significantly grow in length. After the Pork Tapeworm has developed into a fully grown adult, it will then lay eggs in the person's excrement, starting the process over again. [2] 

The distribution of T. solium is very common in urbanized communities where livestock are in close and frequent contact with humans. This is especially so in third world countries where there are few, if any cooking regulations, and under-cooked or unsanitary pork is a commonality. The knowledge of disease causing tapeworms in pigs dates back to Ancient Egypt and is considered the major reason why consumption of pigs are against Jewish and Islamic dietary laws. [4] The effects it has on humans can be fatal, and the prescription medication used to treat it can be costly. The effects of Pork Tapeworm and other parasites like it are a major reason why pork production is so closely scrutinized in the United States.

Example of:

T. solium exemplifies fecal-oral transmission. In fecal-oral transmission, eggs of the parasite are laid in the fecal matter of the primary host, where they are then consumed by an intermediary host. Because of humans close contact with livestock throughout history, parasitic tapeworms like T. solium adapted long ago to develop a life cycle that utilized fecal-oral transmission and allowed for a high level of reproductive success. [5]


[1] "Taenia solium (Pork Tapeworm)" Standford.
[2] "Taeniasis" Laboratory Identification of Parasites of Public Health Concern.
[3] "Cysticercosis" Center For Disease Control and Prevention.
[4] "Ancient Hebrew Medicine" Health Guidance.
[5] "Zoonoses and Veterinary Public Health" World Health Organization.


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