That is to say, I was assigned tapeworms for my report on pathogenic eukaryotes in my microbiology class. Fun stuff.
Taenia saginata is medically important as a parasitic infection of the small intestines. It is of the Kindom Animalia and of the Class Cestoidea. It is commonly referred to as a tapeworm, specifically the “beef tapeworm” because the species also infects cows as an intermediate host. Humans are the definitive host, meaning it is in humans where infection produces a sexually mature adult worm, and T. saginata’s life cycle is completed.
T. saginata is extremely well adapted as an intestinal parasite. Having no digestive system of its own, it absorbs nutrients from its host directly through its skin. The worm’s flat shape maximizes the surface-to-volume ratio which allows for the most efficient absorption of nutrients. The proximal end of the worm attaches itself to the intestinal wall via a structure called the scolex. As the worm grows, it produces a body of proglottids called the strobila and produces, at full maturity, up to 2,000 proglottids reaching a length of 25 meters. The proglottids contain both male and female organs, as well as musculature that allows for some motility. As the strobila grows in length the proglottids fertilze themselves, producing up to 1,000 eggs each. Once the proglottids are gravid (i.e. filled with fertilized eggs), they detach themselves from the end of the strobila where they and their eggs are passed along in the feces of the host into the environment. The eggs have a protective coating called an oncosphere that allows it to remain intact in the environment for up to a month and allows it to survive digestion of the bovine host. Once inside the intestines, the eggs hatch, and the larva migrate to the striated musculature where they encyst themselves and wait to be eaten. This stage of the disease is commonly known as “bovine measles.”
Cooking the meat will kill the cysts; raw or undercooked meat is the primary means of infection. If a viable cyst is ingested, it passes through the host to the small intestines where the host’s own digestive enzymes cause the cyst to hatch into a larva. The larva will attach by the scolex to the epithelial cells of the intestine and mature into an adult, and the life cycle begins again.
T. saginata is infectious worldwide, but it is more prevalent in rural and developing nations where proper treatment of human waste is an issue. It is especially prevalent in places where eating raw meat is culturally widespread, and also places where human feces are used a fertilizer. The single best preventative measure is ensuring your beef is thoroughly cooked.
Surprisingly, infection is often asymptomatic. Because the worm is attached to the host by the scolex at one small point, immune response is limited. Sometimes there are vague symptoms such as mild stomach pain, change in appetite, diarrhea or constipation. Appendicitis may occur in complicated cases. The most diagnostic symptom is proglottids in the feces. Because the eggs are morphologically identical to other species of tapeworm, a proglottid must be observed to verify the diagnosis. Proper diagnosis is extremely important because the related swine tapeworm causes a condition called Neurocystercosis in which cysts form in the brain. This condition may be fatal.
T. saginata is typically treated with niclosamide, a drug that inhibits oxidative phosphorilation in the parasite, usually killing it in a single dose. The worm is then excreted by the host. This drug is the preferred method of treatment because it has a rate of successfully curing the patient above 95%.
As a postscript, I'd just like to mention that as I was researching this report, I discovered mountains of youtube videos about parasites, many of them both fascinating and disgusting, like this video of a squirming tapeworm proglottid, or this video of a girl with a bot fly maggot in her head.
Taenia saginata is medically important as a parasitic infection of the small intestines. It is of the Kindom Animalia and of the Class Cestoidea. It is commonly referred to as a tapeworm, specifically the “beef tapeworm” because the species also infects cows as an intermediate host. Humans are the definitive host, meaning it is in humans where infection produces a sexually mature adult worm, and T. saginata’s life cycle is completed.
T. saginata is extremely well adapted as an intestinal parasite. Having no digestive system of its own, it absorbs nutrients from its host directly through its skin. The worm’s flat shape maximizes the surface-to-volume ratio which allows for the most efficient absorption of nutrients. The proximal end of the worm attaches itself to the intestinal wall via a structure called the scolex. As the worm grows, it produces a body of proglottids called the strobila and produces, at full maturity, up to 2,000 proglottids reaching a length of 25 meters. The proglottids contain both male and female organs, as well as musculature that allows for some motility. As the strobila grows in length the proglottids fertilze themselves, producing up to 1,000 eggs each. Once the proglottids are gravid (i.e. filled with fertilized eggs), they detach themselves from the end of the strobila where they and their eggs are passed along in the feces of the host into the environment. The eggs have a protective coating called an oncosphere that allows it to remain intact in the environment for up to a month and allows it to survive digestion of the bovine host. Once inside the intestines, the eggs hatch, and the larva migrate to the striated musculature where they encyst themselves and wait to be eaten. This stage of the disease is commonly known as “bovine measles.”
Cooking the meat will kill the cysts; raw or undercooked meat is the primary means of infection. If a viable cyst is ingested, it passes through the host to the small intestines where the host’s own digestive enzymes cause the cyst to hatch into a larva. The larva will attach by the scolex to the epithelial cells of the intestine and mature into an adult, and the life cycle begins again.
T. saginata is infectious worldwide, but it is more prevalent in rural and developing nations where proper treatment of human waste is an issue. It is especially prevalent in places where eating raw meat is culturally widespread, and also places where human feces are used a fertilizer. The single best preventative measure is ensuring your beef is thoroughly cooked.
Surprisingly, infection is often asymptomatic. Because the worm is attached to the host by the scolex at one small point, immune response is limited. Sometimes there are vague symptoms such as mild stomach pain, change in appetite, diarrhea or constipation. Appendicitis may occur in complicated cases. The most diagnostic symptom is proglottids in the feces. Because the eggs are morphologically identical to other species of tapeworm, a proglottid must be observed to verify the diagnosis. Proper diagnosis is extremely important because the related swine tapeworm causes a condition called Neurocystercosis in which cysts form in the brain. This condition may be fatal.
T. saginata is typically treated with niclosamide, a drug that inhibits oxidative phosphorilation in the parasite, usually killing it in a single dose. The worm is then excreted by the host. This drug is the preferred method of treatment because it has a rate of successfully curing the patient above 95%.
As a postscript, I'd just like to mention that as I was researching this report, I discovered mountains of youtube videos about parasites, many of them both fascinating and disgusting, like this video of a squirming tapeworm proglottid, or this video of a girl with a bot fly maggot in her head.
