Taeniasis Saginata Infection: Morphology And Lifecycle, Clinical Features, Diagnosis, Treatment And Prevention
Is That A Tapeworm?
Taeniasis Saginata (Beef Tapeworm, Unarmed Tapeworm)
Taeniasis saginata is infection caused by Taenia Saginata. This is the commonest among the large tape worms found in man and is distributed worldwide. Prevalence is highest in areas where beef is a major source of meat. The adult worm grows to a length of 10 meters and may consist of over 2000 segments. It lies free in the jejunum and ileum, the head being attached to the mucosa. The Scolex is 2 mm in diameter and bears no hooklets, but has four suckers. The gravid segments are actively motile and they come out in chains along with feces or wriggle out singly due to their intrinsic muscular action. The uterus has about 20 lateral branches.
The eggs are spherical measuring 30 to 45u in diameter and the eggshell is thick, striated and bile stained. The embryo or onchosphere bears six hooklets and it remains viable for 4 to 8 weeks. The adult worm may live for 10 to 25 years.
Life Cycle Of The Taeniasis Saginata
Man is the definitive host and cattle and Llamas form the intermediate hosts. Eggs passed in feces contaminate soil to be ingested by grazing cattle. The onchospheres are liberated in the intestine and they penetrate the mucosa, enter the blood stream and reach various muscles, mainly those of the heart, tongue, shoulder, neck and loins. On reaching thse sites, the onchospheres lose their hooks and grow into the cystic stage known as cysticercus bovis in 60 to 70 days. The cysticercus is ovoid, measures 8X5 mm and contains a single sprouting scolex. Cysticercus remains viable for 1 to 3 years within the muscles. Heavily infected meat is easy to distinguish by the presence of numerous cysts.
On ingesting undercooked meat, the cyst wall is digested and the head attaches itself to the mucosa and rapidly grows to reach the adult stage in 6 to 8 weeks. A host usually harbours only one or two worms.
Clinical features: Majority are asymptomatic, though vague symptoms such as abdominal pain, diarrhea and increased appetite may occur in a few. The motile segments emerging out of the anus may cause pruritus and anxiety to the host. Appendicitis and biliary obstruction have been reported rarely.
How To Prevent Tenia Saginata Infection
Diagnosis, Treatment And Prevention
Diagnosis: History of passing segments and seeing the segments in feces confirms the diagnosis. The species can be identified by observing the number of lateral branches. An easy method is to press the segment between two glass slides and holding it against light. Taenia saginata segment has more than 15 lateral branches, whereas taenia solium has only less than 13.
Eggs can be demonstrated by microscopic examination of the feces or by examining perianal scotch tape swab. The eggs of T. saginata, T. Solium and T. echinococcus cannot be differentiated from each other.
Treatment: Niclosamide (Yomesan) is the drug of choice. It kills the scolex and segments on contact. Four tablets, each of 0.5g are given as a single dose to be thoroughly chewed in the morning with a gulp of water. The worm is passed partially digested 24 to 36 hours later. If the whole worm including the scolex is not passed, the worm re-grows and segments reappear in stools within 3 months. In this case, the drug is repeated in the same dose.
Prevention: Taenia saginata infection can be prevented by avoiding infected beef, inspection of slaughter houses, and proper disposal of excreta.
© 2014 Funom Theophilus Makama