Significations et usages de Fasciolopsis_buski

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Fasciolopsis is a genus of trematodes. It consists of two species, one of which, Fasciolopsis buski, ^[1] is notable for causing the disease fasciolopsiasis.

Fasciolopsis buski

Fasciolopsis buski is commonly called the giant intestinal fluke. It is a common parasite of humans and pigs and is most prevalent in Asia, mainly central and southeast Asia. It is in 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 Fasciolopsiasis.

Morphology

F. buski is a large leaf-shaped 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. The size of an adult worm can reach up to 3 inches in length and 1 inch in width.

Life Cycle

Adults produce over 25,000 eggs every day which take up to seven weeks to mature and hatch at 27 degree Celsius to 32 degree Celsius. 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 parasites undergo 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. (CDC)

Geographic Distribution

Fasciolopsis buski is mostly found in the continent of Asia. 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.

Symptoms

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.

Laboratory Diagnosis

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 preferable drug 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 anthelminths that can be used include thiabendazole, mebendazole, levamisole and pyrantel pamoate.^[2]

Natural Cure

Black Walnut Green Hull is proven effective against this trematode on his adult phase, for the larvae wormwood is known to help and the eggs cloves are used.

Prevention

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.

Studies

A study conducted by Sadan, E.H. and C. Maiphoom in 1953, has shown that Fasciolopsis 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.

References

 This article incorporates public domain material from the Centers for Disease Control and Prevention document "Fasciolopsiasis".

• Sadun, E.H. and C. Maiphoom. "Studies on the Epidemiology of the Human Intestinal Fluke, Fasciolopsis Buski in Central Thailand." American Journal of Tropical Medicine and Hygiene. 2(6), (1953): 1070-1084.
• Roberts, Larry S. and John Janovy, Jr. "Foundations of Parasitology" New York: McGraw Hill, 2009. (272-273)