There are two members of the Taenia species which are of clinical importance to humans, Taenia solium and Taenia saginata. With few exceptions the two organisms are similar in most respects.The distribution of Taenia saginata and Taenia solium correlates directly with areas of the world where the inhabitants do not practice sanitary conditions and where beef or pork is eaten regularly.Taenia saginata occurs mainly in these cosmopolitan areas, while Taenia solium occurs worldwide.Both organisms need an intermediate host, a cow or a pig, depending on the species.
Morphology of Taenia species
The eggs of Taenia solium and Taenia saginata are indistinguishable. The size is between 28 and 40 µm around 18 to 30 µm. egg measures 33 by 23 µm. The egg consists of a hexacanth embryo including the standard three pairs of hooklets.The embryo is surrounded by a yellow – brown envelope located on selected tapeworm eggs known as embryophores on which radial stripes are found. These eggs may be non embryonated or embryonated.
Taenia Species Egg: Typical Characteristics
|Size range||28-40 µm by 18-30 µm|
|Hooklets||Three pairs; hexacanth embryo|
|Other features||Radial striations on yellow brown embryophore|
The typical Taenia spp. scolex has a diameter of 1 to 2 mm and is equipped with four sucker.The main difference between those of T.saginata and T.Solium is that the latter contains a fleshy rostellum and a double crown (row) of precisely defined hooks, while the former lacks these structures.
Taenia spp. Adult: Typical Characteristics
The average number of segments (proglottids) of typical T.saginata and T.solium adult worms is 1048 and 898, respectively.There are two main differences between the internal structures in the proglottids of both Taenia organisms, appearance and number of uterine branches on each side of the uterus. A T. saginata proglottid saginata proglottid is usually rectangular and has an average of 17.5x 5.5 mm. There are usually 15 to 30 uterine branches on each side of the uterus.In contrast, T.Solium has a square appearance and contains only 7 to 15 uterine branches on each side of the uterus.
Life Cycle of Taenia species
Infection with Taenia spp.occurs after ingestion of raw or undercooked beef (T.saginata) or pork (T.solium) contaminated by a cysticercus larva, a type of larva that consists of a scolex surrounded by a thin – walled bladder-like cyst and filled with fluid.The attachment of the Scolex to the intestinal mucosa takes place after the Larvae develop in the small intestine where they mature into adult worms.The resulting adult reproduces and produces numerous eggs, some of which can get into the faeces.These eggs are then eaten by the right animal species (cow or pig) in which the oncosphere hatches.The oncosphere then migrates via the blood to the animal tissue and transforms into the stage of the infectious Cysticercus larva.A new cycle begins with the human intake of the infected animal meat.
Clinical symptoms of Taeniasis
Most people with Taenia spp infection. Remain typically asymptomatic.
Taeniasis: Beef or Pork Tapeworm Infection
Patients infected with taenia may experience nondescript symptoms such as diarrhea, abdominal pain, changes in appetite and slight weight loss.Symptoms such as dizziness, vomiting and nausea may also develop.Laboratory tests often show moderate eosinophilia (elevated eosinophils).The outlook is usually good.
Laboratory Diagnosis of Taeniasis
Stool is the preferred specimen to recover taenia eggs and gravid proglottids.The scolex can only be seen after the patient has received antiparasitic drugs.There is also evidence that specimens collected around the perianal area using the cellophane tape (scotch tape) preparation procedure lead to a very high recovery rate of Taenia eggs.It is important to note that Taenia ‘s eggs are identical.To specify a gravid proglottid or scolex in the laboratory, it must be recovered and examined.
Treatment of Taeniasis
tapeworm treatment involves a total eradication of the scolex is the most important and in some cases difficult aspect of the treatment of Taenia infections.Fortunately,tapeworm medicine like praziquantel has been shown to be effective against the whole adult worm, but is not used when the eye or central nervous system (CNS) is involved.Alternative treatments may also be used for paromomycin and quinacrine hydrochloride (Atabrine).
Prevention and Control of Taeniasis
tapeworm prevention involves three measures to alleviate Taenia spp.: proper sanitation, thorough pre-consumption cooking of beef and pork and prompt treatment of infected people.While each of these measures breaks the life cycle of the organism by itself, a combination of all three ensures a cleaner environment and a healthier population.
Notes of Interest and New Trends
Human beings have been known to contract a Taenia solium-related human tissue infection called cysticercosis.This happens when a human ingests the Taenia Solium eggs accidentally and are passed through human feces,Contamination of food, water and soil is probably a way to transmit the eggs from person to person.Once in the body, the eggs lose their external cover, allowing the oncosphere to invade the bloodstream and tissues, mainly the voluntary muscles.While some patients remain asymptomatic, symptoms may vary depending on where the infection is located.Brain infection manifestations (neurocysticercosis) are common and may involve headache, convulsions, confusion, ataxia and even death.Treatment, including surgical removal and medication, is available.Immunological tests, including indirect hemagglutination and the enzyme-linked immunosorbent test (ELISA), are available for the diagnosis of cysticercosis.Prevention measures are similar to those for the species of Taenia, thorough pork cooking and proper sanitation.
Infections with Taenia saginata asiatica (Asian Taenia) or Taenia asiatica have been reported in different places in Asia.The majority of cases reported were acquired by eating raw pig liver, although bovine and goat consumption was also involved.Morphologically, Taenia asiatica contains, unlike Taenia saginata, a sunken rostellum and two rows of hooklets.Molecular studies have shown that Taenia saginata and Taenia solium differ from the organism.In contrast to Taenia saginata or Taenia solium infections, multiple adults may be present in Taenia asiatica.Infected people can be asymptomatic or have abdominal pain, nausea, weakness, loss of weight, and headaches.The choice of treatment is praziquantel.