helminthic infection

Taenia saginata (Beef Tapeworm)

In adult stage, T. saginata inhabits the upper jejunum where it may survive for as long as 25 years. It causes intestinal infection, Taeniasis. It has worldwide distribution. These are one of the true and segmented tapeworms. Their body is divided into three regions;
1. Scolex: the hold fast organ
2. Neck: posterior to the scolex
3. Strobilla: the main bulk, made up of proglottids.

Morphology:
Adult worm measures 5-10 meters in length. The pyriform scolex has 4 suckers but no rostellum. The mature segments have irregularly alternate lateral genital pores. The ovary is in the posterior part of the proglottid and has two large lobes. The follicular vitellaria (which produce the eggshell and nutrient yolk cells) lie in a band behind the ovaries. The numerous follicular testes are scattered throughout the anterodorsal part of the proglottid. The vas deferens opens through the muscular cirrus at the common genital pore, which is situated irregularly on alternate lateral margins.
Each of the terminal segments contains only a uterus made up of a median stem with 15-30 lateral branches.

Life cycle
The adult worm lives in the small intestine of man. Gravid segments pass out in the stool and become disintegrated and eggs come out to the soil. The gravid proglottid uterus contains about 100,000 eggs. The egg of T. saginata is round, about 40 microns in diameter. The 6-hooked embryo is enclosed in a radially striated embryophore. Eggs are ingested by an intermediate host, cattle. The 6-hooked embryo escapes from its shell, penetrates through the intestinal wall into the blood vessels and is carried to the muscles where it develops into a larval stage, cysticercus bovis (made up of an invaginated /inverted head and spherical body). Infection to man takes place by the ingestion of raw or insufficiently cooked beef. In the small intestine of man, the head of the cysticercus gets invaginated and the body becomes segmented.




Pathogenecity
Infected persons may complain of epigastric pain, abdominal discomfort, diarrhea, weight loss, hunger sensation, vomiting, these symptoms and signs are possibly caused by toxic products produced by the worms or are allergic reactions, and are characteristically alleviated by taking food.


Treatment:
Praziquantel at a single oral dose of 5–10mg/ kg is usually completely effective.
Niclosamide: Four tablets chewed in a single dose.
Mebendazole 100mg twice daily for three days

Prevention:
-Thorough cooking of meat (above 57?C).
-Proper disposal of human excrete



Taenia solium (Pork Tapeworm)

The adult worms of T. solium reside or inhabit the upper jejunum. Infection has worldwide distribution.

Morphology:
Adult worm measures about 3 meters in length. The globular scolex has rostellum with 2 rows of hooklets. The scolex measures 1 mm in diameter with four large suckers and a conspicuous rostellum with two rows of alternating large and small hooks. There are 25–30 of these hooks, There are less than 1000 proglottids.
The neck region is thin and measures 5–10 mm. Gravid proglottid liberates about 30,000-50,000 eggs. The mature proglottides are roughly square and are super?cially identical to those of T. saginata. There are 7–12 main branches and this is the feature used to differentiate the gravid proglottides in faeces from those of T. saginata .


Life cycle
Embryonated eggs passed with stool are ingested by pig and the embryo is released. It penetrates the intestinal wall and is carried by vascular channels to all parts of the body. After a period of 2-3 months of development the encysted larval stage called cysticerci or bladder worm occurs in the striated muscles of the tongue, neck, trunk brain, eye, and the nervous system. The cysticercus survives for 5 years. Humans become infected by eating pork containing larvae, cysticercus cellulosae. When improperly cooked cysticercus infected meat is eaten by man, the scolex remains undigested and attaches itself to the intestinal wall and chain of proglottids begin to grow to adult worm.

Clinical manifestations
Resembles that of T. saginata infection


Treatment
Praziquantel at 5–10 mg/ kg in a single oral dose is usually completely effective against adult worms.
Niclosamide at an oral dose of 2 g for an adult given in a divided dose over 2 days is effective.

Prevention:
- Treatment of infected persons.
- Thorough cooking of pork and proper processing
- Proper disposal of human excreta (good hygiene/sanitation).


Comparison between Taenia saginata and Taenia solium species

Taenia saginata Taenia solium
Length (m) 5-10 2-3
Proglottid number 1000-2000 800-900
Hooklets Absent Present
Suckers Pigmented Non- Pigmented
Uterus branch 15-30 7-12













Life cycle of Taenia saginata and Taenia solium


















Taenia saginata























Taenia solium