Taeniasis Solium And Cysticercosis: Morphology, Lifecycle, Clinical Manifestations, Treatment And Prevention
Taeniasis Solium And Cysticercosis (Pork Tapeworm, Armed Tapeworm)
The adult of Taenia solium inhabits the small intestine of man; occasionally the larval stage of T.solium may remain encysted in several tissues. This condition is called cysticercosis. Taenia solium is seen all over the world, especially in those countries where pork is a major source of meat. With the availability of CT scanning of brain, more and more cases of cysticercosis are being reported. In India, T. solium is present in all areas, though, it is less common than T. saginata.
Morphology: The adult worm is 3 meters in length and the proglottides are less than a thousand in number. The scolex is globular and 1 mm in diameter. It bears a restellum with a row of hooklets and four suckers. The name solium is derived from the shape of the rostellum which resembles the conventional figure of the sun. The gravid uterus has a main stem with 8 to 10 compound lateral branches on either sides. The worm has a long lifespan extending up to 25 years. Eggs are indistinguishable from those of T. saginata. Larvae are found encysted in tissues. The cyst is oval in shape (5x20mm) and contains an invaginated scolex.
Life cycle: Man is the definitive host. Pigs and occasionally, man form the intermediate hosts. Segments containing eggs passed in human feces are eaten up by pigs. The hexacanth embryos liberated in the intestine of the pig penetrate the gut wall and reach several tissues through the blood stream. Muscles of limbs, tongue and neck are affected more. Within 60 to 70 days, the embryos develop into cysts called cysticercus cellulosae (bladder worm). The cysticerci live up to 8 months after which they die. Heavily infected pork is known as ‘measly pork’. Man gets the infection by eating undercooked infected pork. The larva is liberated in the intestines. It attaches to the jejuna mucosa and grows into adult worm in 2 to 3 months after which segments are passed in stools.
Clinical Manifestations Of Taeniasis Solium: Intestinal infection leads to minimal symptoms or none at all. The patient may complain of passing segments in strips and this may lead to anxiety.
The Clinical Manifestations Of Cysticercosis
When man ingests the eggs or the gravid segments with ova reach the small intestine by reverse peristalsis, the eggshell is digested and larvae escape. The liberated embryo penetrates the mucosa. The larvae are disseminated to various tissues in the circulation and they develop into cysticerci. The cysts are found mostly in the subcutaneous tissues, eyes, brain and bones and they remain viable for three years. Viable cysts do not cause any tissue reaction. When they die, the cysts swell up and provoke foreign body reaction in the tissues and general symptoms in the form of fever, eosinophilia, arthralgia and muscular pain. Ultimately, the cysts get calcified and can be seen in X-rays.
The cysts developing in the nervous system cause focal or general neurological manifestations such as epilepsy, focal neurological deficits referable to brain or spinal cord, rise in intracranial tension and progressive or intermittent hydrocephalus. The commonest presentation is late onset epilepsy. The cysts in the brain do not calcify readily as in other tissues. In the eyes, the cysts provoke uveitis and retinal hemorrhage and they can be seen by ophthalmoscope. In the skin and muscles, they are palpable as small nodules. Sometimes affected muscles undergo pseudohypertrophy.
Diagnosis: It is made by observing the gravid segments or eggs in feces. Cysticercosis is suspected by history and clinical examination. Calcified cysts may be seen by radiological examination of soft tissues. Cysts in the central nervous system can be detected by scanning. Cysticercosis complement fixation test helps in diagnosis in endemic areas.
Drugs To Treat And Prevent Tenia Solium Infection
Treatment And Prevention
- Nicolsamide is effective in killing the adult worms in a dose of 2g, but the worm is disintegrated and this may liberate the ova. Due to the risk of cysticercosis, this drug is better avoided.
- Mepacrine is preferable since it does not cause the danger of cysticercosis. The patient is advised to take a liquid diet for 48 hours. On the previous evening, a Ryles tube is passed and kept in situ. Next morning, at 6a.m, 10 tablets (0.1g each of mepacrine) are dissolved in 100ml of water and introduced through the tube. After 30 minutes, 30 ml concentrated magnesium sulphate is given through the tube and the tube is withdrawn. This is followed by a warm drink. Within 2 hours the entire worm is passed intact. If the scolex is passed, it ensures cure. Mepacrine may colour the mucous membranes yellow and simulate jaundice. At times vomiting may be troublesome, but this is easily prevented by giving any anti-emetic drug.
- Filix mas (male fern) is an age-old remedy for T. solium. After 48 hours of bowel preparation with liquid diet, 2.5ml of fresh extract of filix mas is given early morning in three capsules, one each at 6a.m, 6:15a.m and 6:30a.m. At 7a.m, 60ml concentrated sodium sulphate solution is given. By 9a.m, the worm is expelled. If not, a soap and water enema is given. Food is allowed only after 9:30a.m.
Treatment of cysticercosis is unsatisfactory. For those with epilepsy, treatment is the same as for idiopathic epilepsy with longterm anticonvulsants. The symptoms improve with time when the inflammatory reaction subsides. Operative intervention is needed rarely when focal symptoms or obstructive features develop. There are reports of successful treatment of human cysticercosis with prolonged use of praziquantel. In a dose of 50 mg/Kg for 15 days.
Prevention: The infection can be prevented by cooking pork thoroughly and by proper disposal of human excreta.
© 2014 Funom Theophilus Makama