Fascioliasis is caused by the trematodes Fasciola hepatica (the sheep liver fluke) and Fasciola gigantica, parasites of herbivores that can infect humans accidentally. In agriculture, Fasciola infections cause billions of dollars of losses due to poor meat quality and loss of milk production and condemnation of livers.

Geographic Distribution

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Fascioliasis occurs worldwide. Human infections with F. hepatica are found in areas where sheep and cattle are raised, and where humans consume raw aquatic plants like watercress, including Europe, the Middle East, and Asia. Infections with F. gigantica have been reported, more rarely, in Asia, Africa, and Hawaii. Specific species of snails as intermediate hosts have to be present also (Pulmonata, Genera Lymnaea, Fossaria, Galba, Radix ).

Clinical Features

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During the acute phase (caused by the migration of the immature fluke through the hepatic parenchyma), symptoms include abdominal pain, hepatomegaly (enlarged liver), fever, vomiting, diarrhea, urticaria and eosinophilia, and can last for months. In the chronic phase (caused by the adult fluke within the bile ducts), the symptoms are more distinct and reflect intermittent biliary obstruction and inflammation. Occasionally, ectopic locations of infection (such as intestinal wall, lungs, subcutaneous tissue, and pharyngeal mucosa) can occur.

Laboratory Diagnosis

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Microscopic identification of eggs is useful in the chronic (adult) stage for diagnosis. Eggs can be recovered in the stools or in material obtained by duodenal (small intestine) or biliary drainage. They are morphologically indistinguishable from those of the fluke F. buski. False fascioliasis (pseudofascioliasis) refers to the presence of eggs in the stool resulting not from an actual infection but from recent ingestion of infected livers containing eggs. This situation (with its potential for misdiagnosis) can be avoided by having the patient follow a liver-free diet several days before a repeat stool examination. Antibody detection tests are useful especially in the early invasive stages, when the eggs are not yet apparent in the stools, or in ectopic fascioliasis.

Treatment

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Unlike infections with other flukes, F. hepatica infections may not respond to Praziquantel. The drug of choice is triclabendazole with bithionol as an alternative.

High prevalence in the Bolivian Altiplano

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In the high plane of Bolivia, about 15% of the population is infected with Fasciola hepatica:

• "Case-control analysis indicated that the only factor associated with illness was eating kjosco (an aquatic plant) while tending animals in the fields; 27 (52%) of the 52 case-patients vs. 9 (14%) of the 66 controls ate kjosco (OR = 6.84; 95% CI = 2.60, 18.44)...... Fascioliasis is a significant human health problem and is highly endemic in the Aymara Indian community in the Bolivian Altiplano. Efforts to prevent fascioliasis should include educating people to avoid eating uncooked aquatic plants such as kjosco." cited from: An outbreak of acute fascioliasis among Aymara Indians in the Bolivian Altiplano. (1996) ^*.

• "Humans are infected by drinking contaminated fresh or field water, or by consuming uncooked aquatic plants, especially watercress (berro), algae (algas), tortora (corr.:Totora), and kjosco." cited from: Hypereosinophilia and liver mass in an immigrant, 2002, ^*.

• "Contamination with Fasciola metacercariae of herbage and semi-aquatic plants grown in a swamp in one of these areas was biologically assessed, using guinea pigs. Plants of Compositae and Eleocharis spp. were contaminated most intensely and those of Senecio sp. and Vallisneria sp. carried a fairly large number of cysts, while plants of Scirpus sp. and Ranunculaceae carried only a few cysts. No signs of Fasciola infection were observed in any animal given the plants of Liliaceae." cited from: Inst Anim Health Q (Tokyo). 1975 Summer;15(2):61-7. Fascioliasis of livestock and snail host for Fasciola in the Altiplano Region of Bolivia. Ueno H, Arandia R, Morales G, Medina G.

External links

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• Extensive Paper on: The Life cycle of Fasciola hepatica, Stewart J. Andrews Pdf, 205 Kb (only missing a clarification if drinking water could be infective: "Encystment may also take place upon the surface of the water (Wright, 1927)")
• Fascioliasis @ CDC
• http://www.emedicine.com/ped/topic760.htm :"When humans consume contaminated plants or water....."

Parasitic diseases

Großer Leberegel | Fascioliasi umana | Leverbotziekte | Fasciolíase