Parasitology

Topics: Digenea, Fasciolopsis buski, Digestion Pages: 6 (1634 words) Published: August 26, 2013
INTESTINAL FLUKES

Fasciolopsis buski

Fasciolopsis buski is a genus of trematodes. It is a notable parasite of medical importance in humans and veterinary importance in pigs. The term for infestation with Fasciolopsis is fasciolopsiasis. Fasciolopsis buski is commonly called the giant intestinal fluke, because it is an exceptionally large parasitic fluke, and the largest known to parasitize humans. Its size is variable and a mature specimen might be as little as 2 cm long, but the body may grow to a length of 7.5 cm and a width of 2.5 cm. It is a common parasite of humans and pigs and is most prevalent in Southern and Southeastern Asia. Fasciolopsis buski generally occupies the upper region of the small intestine, but in heavy infestations can also be found in the stomach and lower regions of the intestine.

In London, George Busk first described Fasciolopsis buski in 1843 after finding it in the duodenum of a sailor. After years of careful study and self-experimentation, in 1925, Claude Heman Barlow determined its life cycle in humans. The giant intestinal fluke F. buski is found in China (including Taiwan), Vietnam, and Thailand, and parts of Indonesia, Malaysia, and the Indian subcontinent. Adult worm live attached to the bowel wall, primarily in the duodenum and jejunum, in heavy infection they may be found throughout the intestinal tract. Their lifespan seldom exceeds 6 months. An estimated 10 million infection occur annually.

Infection is acquired by ingestion of the metacercariae, encysted on fresh-water vegetation such as bamboo, shoots or water chestnuts, which may be consumed raw or peeled with the teeth. Reservoir hosts include pigs, dogs and rabbits.

Adult worms are seen only following purgation after specific anthelminthic treatment. They are fleshy worms, 2 to 7.5 cm long by 0.8 to 2 cm wide. The ellipsoid eggs are yellow-brown in color. The shell is transparent, with a small operculum at the more pointed end. Eggs are unembryonated when first passed, containing early cleavage stages; they measure 130 to 140 um by 80 to 85 um.

Life cycle

Adults produce over 25,000 eggs every day which take up to seven weeks to mature and hatch at 27–32 °C. Immature, unembryonated eggs are discharged into the intestine and stool. In two weeks, eggs become embryonated in water, and after about seven weeks, eggs release tiny parasitic organisms called miracidia, which invade a suitable snail intermediate host. The definitive hosts are humans and pigs, while the intermediate host is the Segmentina.

Symptoms and Pathogenesis

The attachment of these large worms to the mucosa of the bowel causes local inflammation and ulceration, sometimes accompanied by hemorrhage. Few worms do not give rise to any symptoms but heavier infections leads abdominal pain, duodenal ulcer disease and diarrhea. The stools profuse light yellow in color. Vitamin B12 absorption is impaired. Intestinal obstruction may occur. Edema and ascites develops, hypoalbuminema resulting from long-continued malabsorption from a protein-wasting enteropathy. Marked eosinophilia is usually seen

Treatment

The drug of choice is paraziquantel (biltricied), sn isoquino-linepyrazine derivative, it is administered orally, 23mg/kg body weight three times in 1 day

The Echinostomes

They are a number of medium sized intestinal flukes belonging to the genus Echinostima. The live attached to the wall of the small intestine, they average under 1 cm in length and 0.2 cm in width and are distinguished by a collarette of spines on a disk surrounding the oral sucker. The most important species is Echinostoma ilocanu. The adult worms are seen only after treatment.

Symptoms and Pathogenesis

May produce inflammation and mild ulceration, with diarrhea and abdominal pain

Treatment

The drug of choice is praziquantel 25 mg/kg body weight three times in a single day. tetracholorehtylene, doe is 0.1 ml/kg...
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