Fasciolopsis is a genus of trematodes. It consists only of two species, F. buski and F. Magna, of which, F. buski,is more notable in terms of prevalence and pathogenicity as it causes the disease fasciolopsiasis.


Fasciolopsis buski is commonly called the giant intestinal fluke, being the largest known parasitic fluke in humans. The body can be up to 7.5 cm in length and 2.5 cm in width. It is a common parasite of humans and pigs and is most prevalent in Asia, mainly central and southeast Asia. It belongs to the class Trematoda, family Fasciolidae. The reason for its common name is due to the fact that it is one of the largest flukes to infect humans. The worm inhabits the upper region of the small intestine and, when abundant, can also be found in the lower areas of the intestine and the stomach. Fasciolopsis buski is the cause of the disease fasciolopsiasis. In London, George Busk first described F. buski in 1843 after finding it in the duodenum of a sailor. In 1925, Barlow first determined its life cycle in humans.

F. buski is a large leaf-shaped, dorso-ventrally flattened worm that is characterized by a blunt anterior end, undulating, unbranched ceca (sac-like cavity with a single opening), tandem, dendritic testes, branched ovaries, and ventral suckers to attach itself to the host. The acetabulum is larger than the oral sucker. It has extensive vitelline follicles. It can be distinguished from other fasciolids by a lack of cephalic cone or "shoulders" and the unbranched ceca.

Most infections are light and asymptomatic. In heavy infections, symptoms can include abdominal pain, chronic diarrhea, anemia, ascites, toxemia, allergic responses, sensitization caused by the absorption of the worms allergenic metabolites (may eventually cause death of patient), and intestinal obstruction.

Microscopic identification of eggs, or more rarely of the adult flukes, in the stool or vomitus is the basis of specific diagnosis. The eggs are indistinguishable from those of Fasciola hepatica.

Treatment Praziquantel is the drug of choice for treatment. Treatment is effective in early or light infections. Heavy infections are more difficult to treat. Studies of the effectiveness of various drugs for treatment of children with F. buski have shown tetrachloroethylene as capable of reducing faecal egg counts by up to 99%. Other anthelmintics that can be used include thiabendazole, mebendazole, levamisole and pyrantel pamoate. oxyclozanide, hexachlorophene and nitroxynil are also highly effective.

Black walnut green hull is proven effective against this trematode on his adult phase, for the larvae wormwood is known to help, and for the eggs cloves are used. Flemingia vestita and Lysimachia ramosa are used by the Khasi tribes of India, and the extracts were shown to effectively obliterate F. buski. Alpinia nigra, used by many tribals of north-east India for deworming also caused significant efficacy.

Prevention can be easily achieved by immersion of vegetables in boiling water for a few seconds to kill the infective metacercariae, avoiding the use of nightsoil as a fertilizer, and maintenance of proper sanitation and good hygiene. Additionally, snail control should be attempted.

F. buski is endemic in Asia including China, Taiwan, South-East Asia, Indonesia, Malaysia and India. It has a prevalence of up to 60% in India and mainland China and has an estimated 10 million human infections. Infections occur most often in school-age children or in impoverished areas with a lack of proper sanitation systems. A study revealed that F. buski was an endemic in central Thailand, effecting approximately 2,936 people due to infected aquatic plants called water caltrops and the snail hosts which were associated with them. The infection, or the eggs which hatch in the aquatic environment were correlated with the water pollution in different districts of Thailand such as Ayuthaya Province. The high incidence of infection was prevalent in females and children ages 10-14 years of age.


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. Several species of genera Segmentina and Hippeutis serve as intermediate hosts. In the snail the parasite undergoes several developmental stages (sporocysts, rediae, and cercariae). The cercariae are released from the snail and encyst as metacercariae on aquatic plants such as water chestnut, water caltrop, lotus, bamboo, and other edible plants. The mammalian host, or the final host, becomes infected by ingesting metacercariae on the aquatic plants. After ingestion, the metacercariae excyst in the duodenum in about three months and attach to the intestinal wall. There they develop into adult flukes (20 to 75 mm by 8 to 20 mm) in approximately 3 months, attached to the intestinal wall of the mammalian hosts (humans and pigs). The adults have a life span of about one year.

Life cycle of Babesia microti


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