Found in over 50 countries where people engage in sheep and cattle production, fascioliasis is caused by two types of parasitic flatworm, or trematode (Fasciola hepatica and Fasciola gigantica). The disease affects the liver and bile ducts. Chronic fascioliasis infection causes abdominal pain, inflammation, and the formation of scar tissue and fibrosis in the bile duct. While not fatal in people, fascioliasis can cause significant economic damage for farmers who lose their livestock as a result of liver damage. The disease occurs much more frequently in animals; however, the CDC estimates that more than 2 million people are infected worldwide. The Andean highlands of Bolivia and Peru have the highest known rates of human fascioliasis infection.
Here are some of the most common questions about detecting and treating fascioliasis:
1. How is fascioliasis spread?
Fascioliasis is a zoonotic disease, meaning it can be transmitted from animals to people. While the life cycle of the Fasciola parasite is complex, infection essentially spreads through the consumption of aquatic plants (such as watercress) or water contaminated with Fasciola cysts. Such contamination occurs when an infected animal defecates into a water source. People can also contract the disease by eating the livers of infected animals or through the fecal-oral route.
2. What are the symptoms of fascioliasis?
Fascioliasis often does not present with symptoms in the early stages of infection, but some people and animals will experience nausea, vomiting, abdominal pain and inflammation, fever, gastrointestinal bleeding, and diarrhea. As the infection progresses, it causes scar tissue to build up in the bile ducts, leading to fibrosis and obstruction of the ducts. Chronic infection can also cause inflammation of the liver, gallbladder, and pancreas.
3. How is fascioliasis diagnosed?
Since Fasciola parasites are visible to the naked eye, the most common way to test for fascioliasis involves looking for eggs in a stool or bile sample. However, this method does not work 100 percent of the time, as infected hosts do not begin passing eggs until they have been infected for several months. In the earlier stages of infection, the disease can be diagnosed through blood tests to detect the presence of immunoglobulin (IgG) or immunoglobulin M (IgM) antibodies to the Fasciola parasite. Sometimes several rounds of blood or fecal testing is necessary to confirm a diagnosis.
4. How is fascioliasis treated?
Once a firm diagnosis of fascioliasis has been made, treatment centers on the use of Triclabendazole, an anthelmintic (a drug that expels parasitic worms from the body). Most patients will only require a single oral dose of the drug. While veterinary resistance to Triclabendazole is spreading, there have not yet been any reports of human resistance to the drug.
5. What can I do to protect myself (or my livestock) from fascioliasis?
There is currently no vaccine for fascioliasis for either humans or animals, so proper preventive measures need to be taken. In areas where the Fasciola parasite is endemic, public health programs can be put in place to limit the spread of the disease. These include vector control by chemically treating water sources, restricting the growth and sale of aquatic plants like watercress for human consumption, limiting animals’ access to aquatic plants, and enforcing adequate separation between humans and livestock. You should avoid eating raw watercress, particularly from areas where infection is endemic, and you should always thoroughly cook vegetables grown in fields that may have been irrigated with contaminated water. In addition, never eat raw liver or other viscera.
Center for Disease Control (CDC). “Parasites- Fascioliasis (Fasciola infection).” Available at https://www.cdc.gov/parasites/fasciola/.
Tewoderos, S. and D. Scott Smith. 2006. “Fascioliasis.” Stanford University. Available at https://web.stanford.edu/group/parasites/ParaSites2006/Fascioliasis/facioliasis.html.
World Health Organization (WHO). “Fascioliasis diagnosis, treatment, and control strategy.” Available at http://www.who.int/foodborne_trematode_infections/fascioliasis/fascioliasis_diagnosis/en/.