Fascioliasis is a zoonotic infection caused by the foodborne trematode, Fasciola hepatica, with global prevalence, especially endemic in sheep and cattle-raising areas of South America, the Caribbean, northern Africa and western Europe [1]. Adult flukes are flat, brown, leaf shaped worms, measuring up to 3 cm in length. Sheep liver fluke infestation results from ingestion of larvae encysted on uncooked watercress or other fresh aquatic vegetation like water caltrops, water lettuces, mint or parsley, typically found near infected animals, or through consumption of metacercariae-contaminated water [2]. These cercariae can remain viable on vegetation for months.
The infective metacercariae excyst after being swallowed. The juveniles penetrate the intestinal wall, migrate through the peritoneal cavity and liver capsule, and feed on liver parenchyma before entering the biliary tract, where they mature and release 20,000 to 24,000 eggs per fluke per day [1,3]. The acute hepatic migratory phase of the life cycle occurs within 6 to 12 weeks of ingestion of metacercariae. After 3 to 4 months, the worms enter the biliary tract where they mature and remain as adults. Adult flukes can live for as long as 10 years in humans, who are accidental final hosts [1].
F. hepatica in the acute hepatic migratory phase can cause right upper quadrant pain, intermittent high fever, weight loss, urticaria, jaundice, anemia and eosinophilia. Interestingly, this patient had high absolute eosinophils, which is uncommon during the biliary chronic phase of the F. hepatica infection. In the chronic phase, F. hepatica infection may be subclinical or may cause progressive inflammation with bile duct dilatation and fibrosis related to mechanical obstruction of the ducts and the activity of proline, which the fluke excretes to facilitate movement through the narrow ducts [2]. Anemia may result from blood loss through bile duct lesions. The origin of this patient’s anemia likely resulted from chronic Fasciola infestation. Case reports suggest mortality from hematobilia more commonly in children [1].
The diagnosis of fascioliasis is often difficult due to non-specific clinical symptoms and low suspicion due to its rarity in the West. Computerized tomographic scan and ultrasonographic findings may suggest biliary pathology that prompts further endoscopic evaluation, as in this patient who underwent MRCP showing a mass-like lesion suggestive of cholangiocarcinoma. Definitive diagnosis of fascioliasis can be made by visual detection of living flukes by laparotomy or endoscopic imaging and observation of eggs in the stool. The presence of F. hepatica ova in this patient’s stool confirmed chronic infection, as only mature adult flukes will release eggs. Fasciola specific serological response occurs within 2 to 4 weeks of infection and is helpful to detect active infection [2]. Serology should revert to negative within one year of successful treatment.
A single dose of triclabendazole, which is a well-tolerated benzimidazole used in veterinary practice, is the regimen of choice against fascioliasis. Triclabendazole is highly effective against mature and immature flukes with high cure rates (reportedly 78% to 99%) [1, 4]. Treatment should be repeated with a second dose if radiologic findings or eosinophilia fail to resolve or serologic titers do not decrease. This patient was treated with two doses of triclanbendazole given severity of anemia, eosinophilia and jaundice associated with high worm burden. Concurrent administration of the anti-spasmodic agent hyocyamine appeared to mitigate abdominal pain associated with fasciolicide [4].
Prevention of fascioliasis involves strategic treatment or immunization of herbivorous animals that maintain the life cycle as well as health education to discourage the consumption of raw watercress and other edible water plants [2]. Our patient reported enjoying raw watercress salads weekly for many years, even prior to immigration from Mexico to the United States one year ago.
ID week Fellows' Day 2018 - oral presentation
This case was contributed by:
Erin N. Dizon, MD (1), Paul Holtom, MD, FIDSA, FSHEA (1) and Susan M. Butler-Wu, PhD, D(ABBM) (2)
(1) Los Angeles County + University of Southern California Medical Center, Los Angeles, CA
(2) Clinical Microbiology Laboratory, LAC-USC Medical Center, Los Angeles, CA
The case was originally presented at ID Week 2018, a joint effort of Infectious Diseases Society of America (IDSA), HIV Medical Association, Pediatric Infectious Diseases Society (PIDS), and the Society for Healthcare Epidemiology of America (SHEA), during an interactive session on Fellows' Day. Copyright Infectious Disease Society of America (IDSA), 2018. Used with permission.
Last reviewed: 9 March 2019