History
Approximately 15% of the infected patients are symptomatic; the majority are asymptomatic. [12]
The clinical course of fascioliasis can be divided into four phases. [22]
Incubation period: The period from ingestion of metacercariae to appearance of first symptom. This period can range from a few days to a few months.
Acute phase: The period of migration of larvae from the peritoneal cavity to the biliary tree and liver. This period ranges from 2-4 months. Localized or generalized allergic and toxic reactions mark this phase characterized by fever, generalized or right upper quadrant pain, hepatomegaly, loss of appetite, flatulence, nausea and diarrhea, cough, shortness of breath, chest pain, and urticaria.
Latent phase: This asymptomatic phase involves the period of maturation of the parasite and beginning of oviposition. This period can range from months to years. It is marked by eosinophilia and rarely do relapses of GI symptoms of the acute phase occur in this phase.
Chronic phase: This phase is marked by inflammation, hyperplasia and thickening of the bile ducts and gall bladder, leading to obstruction. The symptoms of this phase such as biliary colic, nausea, intolerance to fatty food, right upper quadrant pain, epigastric pain, obstructive jaundice, and pruritus, are the result of a blockade in the biliary tract and inflammation in the gall bladder. Biliary lithiasis is another manifestation of the chronic phase.
Ectopic fascioliasis can occur due to migration of the larvae to sites other than liver. Commonly involved organs are GI tract, abdominal wall subcutaneous tissue, pancreas, spleen, heart, lungs, and skeletal muscles. Neurofascioliasis and ophthalmofascioliasis has also been reported. [23]
Patients may present with painful or pruritic subcutaneous nodules, although this condition is rare. Halzoun/marrerra manifests with severe pharyngitis, dysphagia, foreign body sensation, and/or airway obstruction.
Physical Examination
Physical examination typically reveals no specific signs of infection.
Abdominal tenderness may be general or may be localized to the right hypochondrium, right upper quadrant, gall bladder, mid epigastrium, or left upper quadrant.
Tender or non-tender hepatomegaly may occur.
Patients often have fever, pallor, and/or evidence of weight loss.
Less often, patients present with urticaria, wheezing, subcutaneous nodules as large as 6 cm in diameter, or other manifestations of ectopic larval migration to the skin, lungs, heart, brain, eye, intestine, and genitourinary tract.
Patients with halzoun/marrerra may have severe pharyngitis and/or laryngeal edema.
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Life cycle of Fasciola hepatica. Immature Fasciola eggs are discharged in the biliary ducts and in the stool (1). Eggs become embryonated in water (2), eggs release miracidia (3), which invade a suitable snail intermediate host (4), including the genera Galba, Fossaria and Pseudosuccinea. In the snail, the parasites undergo several developmental stages (sporocysts (4a), rediae (4b), and cercariae (4c)). The cercariae are released from the snail (5) and encyst as metacercariae on aquatic vegetation or other surfaces. Mammals acquire the infection by eating vegetation containing metacercariae. Humans can become infected by ingesting metacercariae-containing freshwater plants, especially watercress (6). After ingestion, the metacercariae excyst in the duodenum (7) and migrate through the intestinal wall, the peritoneal cavity, and the liver parenchyma into the biliary ducts, where they develop into adult flukes (8). Courtesy of the CDC's DPDx, Division of Parasitic Diseases and Malaria.
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Adult Fasciola hepatica fluke stained with carmine (30 mm by 13 mm). Courtesy of the CDC's DPDx, Division of Parasitic Diseases and Malaria.
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Fossaria bulamoides, a snail host for F hepatica in the western United States. Courtesy of the CDC's DPDx, Division of Parasitic Diseases and Malaria (Conchology, Inc, Mactan Island, Philippines).
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Fasciola hepatica egg in an unstained wet mount (400x magnification). F hepatica eggs are broadly ellipsoidal, operculated, and measure 130-150 μm by 60-90 μm. Courtesy of the CDC's DPDx, Division of Parasitic Diseases and Malaria.
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Adult of F hepatica observed with ERCP imaging in the common bile duct of a human patient. Courtesy of the CDC's DPDx, Division of Parasitic Diseases and Malaria (Dr. Subhash Agal, Kokilaben Dhirubhai Ambani Hospital, Mumbai, India).
