What is fascioliasis? In what parts of the world if fascioliasis found? How do people get infected with fascioliasis? What are the signs and symptoms of Fasciola infection, and when do they begin? How is Fasciola infection diagnosed? Can Fascioliasis be treated? How can fasciola infection be prevented?

1. FASCIOLA
CDC: DECEMBER 31, 2018

2. FASCIOLAABOUT
•Fascioliasis is a parasitic infection typically caused by Fasciola hepatica, which is
also known as “the common liver fluke” or “the sheep liver fluke.” A related
parasite, Fasciola gigantica, also can infect people. Fascioliasis is found in all
continents except Antarctica, in over 70 countries, especially where there are
sheep or cattle. People usually become infected by eating raw watercress or other
water plants contaminated with immature parasite larvae. The young worms
move through the intestinal wall, the abdominal cavity, and the liver tissue, into
the bile ducts, where they develop into mature adult flukes that produce eggs.
The pathology typically is most pronounced in the bile ducts and
liver. Fasciola infection is both treatable and preventable.

3. IMAGES ABOVE :
LEFT: 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.
CENTER: ADULT FASCIOLA HEPATICA FLUKE STAINED WITH CARMINE (30MM X 13MM).
RIGHT: FOSSARIA BULAMOIDES, A SNAIL HOST FOR F. HEPATICA IN THE WESTERN UNITED STATES.

4. WHAT IS FASCIOLIASIS?
•Fascioliasis is an infectious disease caused by Fasciola parasites, which are flat
worms referred to as liver flukes. The adult (mature) flukes are found in the bile
ducts (the duct system of the liver) of infected people and animals, such as sheep
and cattle. In general, fascioliasis is more common in livestock and other animals
than in people.
•Two Fasciola species (types) infect people. The main species is Fasciola hepatica,
which is also known as “the common liver fluke” and “the sheep liver fluke.” A
related species, Fasciola gigantica, also can infect people.

5. IN WHAT PARTS OF THE WORLD IF FASCIOLIASIS FOUND?
•Fascioliasis is found in more than 70 countries, especially where sheep or cattle
are reared. Fasciola hepatica is found in all continents except Antarctica. Fasciola
gigantica has been found in some tropical areas. Except for parts of Western
Europe, human fascioliasis has mainly been documented in developing countries.

6. HOW DO PEOPLE GET INFECTED WITH FASCIOLIASIS?
•People get infected by accidentally ingesting (swallowing) the parasite. The main
way this happens is by eating raw watercress or other contaminated freshwater
plants. Another way people might get infected is by ingesting contaminated
water, such as by drinking it or by eating vegetables that were washed or irrigated
with contaminated water.

7. CAN FASCIOLA BE SPREAD DIRECTLY FROM ONE
PERSON (OR ANIMAL) TO ANOTHER?
•No. Fasciola cannot be passed directly from one person to another. The eggs
passed in the stool of infected people (and animals) need to develop (mature) in
certain types of freshwater snails, under favorable environmental conditions, to
be able to infect someone else.
•Under unusual circumstances, people might get infected by eating raw or
undercooked sheep or goat liver that contains immature forms of the parasite.

8. WHAT ARE THE SIGNS AND SYMPTOMS OF FASCIOLA
INFECTION, AND WHEN DO THEY BEGIN?
•Some infected people don’t ever feel sick.
•Some people feel sick early on in the infection, while immature flukes are passing (migrating)
from the intestines through the abdominal cavity and liver. Symptoms from the acute
(migratory) phase can start as soon as a few days after the exposure (typically, <1–2 weeks) and
can last several weeks or months.
•Some people feel sick during the chronic phase of the infection, when adult flukes are in the bile
ducts (the duct system of the liver). The symptoms, if any, associated with this phase can start
months to years after the exposure. For example, symptoms can result from inflammation and
blockage of bile ducts.
•During both phases of the infection, clinical features can include fever, malaise, abdominal pain,
eosinophilia, hepatomegaly (an enlarged liver), and abnormal liver tests.

9. HOW IS FASCIOLA INFECTION DIAGNOSED?
•The infection typically is diagnosed by examining stool (fecal) specimens under a
microscope. The diagnosis is confirmed if Fasciola eggs are seen. More than one
specimen may need to be examined to find the parasite. Certain types of blood
tests also may be helpful for diagnosing Fasciola infection.

10. CAN FASCIOLIASIS BE TREATED?
•Yes. Fascioliasis is a treatable. Triclabendazole is the drug of choice. It is given by
mouth, usually in twodisease doses. Most people respond well to the treatment.

11. HOW CAN FASCIOLA INFECTION BE PREVENTED?
•People can protect themselves by not eating raw watercress and other water
plants, especially from Fasciola–endemic grazing areas. As always, travelers to
areas with poor sanitation should avoid food and water that might be
contaminated. No vaccine is available to protect people against Fasciola.

12. EPIDEMIOLOGY & RISK FACTORS
•Fascioliasis occurs in many areas of the world and usually is caused by F. hepatica, which is a
common liver fluke of sheep and cattle. In general, fascioliasis is more common and widespread
in animals than in people. Even so, the number of infected people in the world is thought to
exceed two million.
•Fasciola hepatica is found in focal areas of more than 70 countries, in all continents except
Antarctica. It is found in parts of Latin America, the Caribbean, Europe, the Middle East, Africa,
Asia, and Oceania. Fasciola gigantica is found in fewer geographic regions. Human cases have
been reported in the tropics, in parts of Africa and Asia, and also in Hawaii.
•In some areas where fascioliasis is found, human cases are uncommon (sporadic). In other areas,
human fascioliasis is very common (hyperendemic). For example, the areas with the highest
known rates of human infection are in the Andean highlands of Bolivia and Peru.

13. Infective Fasciola larvae (metacercariae) are found in contaminated water—
typically, stuck to (encysted on) water plants or, potentially, floating in the
water—such as in marshy areas, ponds, or flooded pastures. The main way
people (and animals) become infected is by eating raw watercress or other
contaminated water plants (for example, if the plants are eaten as a snack or in
salads or sandwiches). Some data suggest people also might get infected by
ingesting contaminated water, such as by drinking it or by eating vegetables
that were washed or irrigated with contaminated water. Under unusual
circumstances, infection might result from eating raw or undercooked sheep or
goat liver that contains immature forms of the parasite.
The possibility of becoming infected in the United States should be
considered, despite the fact that few locally acquired cases have been
documented. The prerequisites for the Fasciola life cycle exist in some parts of
the United States. In addition, transmission because of imported contaminated
produce could occur, as has been documented in Europe.

14. CAUSAL AGENT
•The trematodes Fasciola hepatica (also known as the common liver fluke or the
sheep liver fluke) and Fasciola gigantica are large liver flukes (F. hepatica: up to 30
mm by 15 mm; F. gigantica: up to 75 mm by 15 mm), which are primarily found in
domestic and wild ruminants (their main definitive hosts) but also are causal
agents of fascioliasis in humans.
•Although F. hepatica and F. gigantica are distinct species, “intermediate forms”
that are thought to represent hybrids of the two species have been found in parts
of Asia and Africa where both species are endemic. These forms usually have
intermediate morphologic characteristics (e.g. overall size, proportions), possess
genetic elements from both species, exhibit unusual ploidy levels (often triploid),
and do not produce sperm. Further research into the nature and origin of these
forms is ongoing.

16. LIFE CYCLE:

17. DISEASE
•Human fascioliasis is usually recognized as an infection of the bile ducts and liver, but infection
in other parts of the body can occur.
•In the early (acute) phase, symptoms can occur as a result of the parasite’s migration from the
intestines to and through the liver. Symptoms can include gastrointestinal problems such as
nausea, vomiting, and abdominal pain/tenderness. Fever, rash, and difficulty breathing may
occur.
•During the chronic phase (after the parasite settles in the bile ducts), the clinical manifestations
may be similar or more discrete, reflecting inflammation and blockage of bile ducts, which can
be intermittent. Inflammation of the gallbladder and pancreas also can occur.

18. DIAGNOSIS
•The standard way to be sure a person is infected with Fasciola is by
seeing the parasite. This is usually done by finding Fasciola eggs in stool
(fecal) specimens examined under a microscope. More than one
specimen may need to be examined to find the parasite. Sometimes eggs
are found by examining duodenal contents or bile.
•Infected people don’t start passing eggs until they have been infected for
several months; people don’t pass eggs during the acute phase of the
infection. Therefore, early on, the infection has to be diagnosed in other
ways than by examining stool. Even during the chronic phase of infection,
it can be difficult to find eggs in stool specimens from people who have
light infections.
•Certain types of blood tests can be helpful for diagnosing Fasciola
infection, including routine blood work and tests that detect antibodies
(an immune response) to the parasite.
FASCIOLA HEPATICA EGG IN AN
UNSTAINED WET MOUNT
F. HEPATICA EGGS ARE
BROADLY ELLIPSOIDAL,
OPERCULATED, AND MEASURE
130–150 ΜM BY 60–90 ΜM.

19. TREATMENT
•The first step is to make sure the diagnosis is correct. For more information,
patients should consult their health care provider. Health care providers may
consult with CDC staff about the diagnosis and treatment of fascioliasis.
•The drug of choice is triclabendazole. The drug is given by mouth, usually in two
doses. Most people respond well to the treatment.

20. PREVENTION & CONTROL
•No vaccine is available to protect people against Fasciola infection.
•In some areas of the world where fascioliasis is found (endemic), special control programs are in
place or are planned. The types of control measures depend on the setting (such as
epidemiologic, ecologic, and cultural factors). Strict control of the growth and sale of watercress
and other edible water plants is important.
•Individual people can protect themselves by not eating raw watercress and other water plants,
especially from Fasciola-endemic grazing areas. As always, travelers to areas with poor sanitation
should avoid food and water that might be contaminated (tainted). Vegetables grown in fields
that might have been irrigated with polluted water should be thoroughly cooked, as should
viscera from potentially infected animals.