Liver Fluke: What You Need to Know About This Parasitic Infection

What are liver flukes?

Liver flukes are leaf-shaped parasitic flatworms that infect the liver, gallbladder, and bile ducts in humans. They belong to the class Trematoda and are a type of trematode infection. Adult flukes can grow up to 10-30mm in length and live for years within the liver, feeding on bile and blood. If left untreated, liver fluke infections can lead to serious complications.

What are the types of liver flukes?

Several liver fluke types or species can infect humans:

• Clonorchis sinensis (Chinese or oriental liver fluke): Found in Asia, especially Korea, China, and Vietnam
• Opisthorchis viverrini: Prevalent in Southeast Asia, particularly Thailand, Laos, and Cambodia
• Opisthorchis felineus: Occurs in Eastern Europe and the former Soviet Union
• Fasciola hepatica (common liver fluke or sheep liver fluke): Found worldwide in temperate climates
• Fasciola gigantica: This liver fluke type is distributed in tropical regions of Africa and Asia

What are the symptoms of liver fluke infections?

Liver fluke symptoms can vary depending on the stage and severity of infection. In the acute phase, as immature flukes migrate through the intestines to the liver, common symptoms include:

• Abdominal pain
• Fever
• Nausea and vomiting
• Diarrhea
• Hives or itchy rash
• Cough
• Muscle aches

As the infection becomes chronic, adult flukes inhabit the bile ducts and cause liver fluke symptoms such as:

• Jaundice (yellowing of skin and eyes)
• Indigestion
• Fatty food intolerance
• Weight loss
• Enlarged liver
• Bile duct obstruction
• Gallstones
• Pancreatitis

Many people with liver fluke have no symptoms for years, while the parasites slowly damage the biliary system. When symptoms do occur, they are often similar to other digestive disorders, making diagnosis challenging.

What causes a liver fluke infection?

Liver fluke causes centres around consuming food or water contaminated with fluke larvae. The microscopic larvae are released from infected snails into freshwater habitats. They then encyst on aquatic plants or within the flesh of freshwater fish and crustaceans. When humans eat these contaminated foods raw or undercooked, the larvae are ingested.

How do you get a liver fluke?

You can contract liver flukes by:

• Eating raw, undercooked, dried, salted, or pickled freshwater fish that contains larvae of Clonorchis sinensis or Opisthorchis species.
• Consuming water plants like watercress contaminated with encysted larvae of Fasciola hepatica or Fasciola gigantica.

Are liver flukes contagious?

No, you cannot get liver flukes directly from an infected person. Liver fluke eggs passed in human faeces must reach freshwater and infect snails to continue their lifecycle. It's only by ingesting cysts in contaminated fish or water that humans acquire the infection. However, poor sanitation allows the flukes to spread between humans, snails and fish in an ongoing cycle.

What are the risk factors for liver fluke infection?

Factors that increase your risk of liver fluke include:

• Eating raw or undercooked freshwater fish in fluke-endemic areas
• Consuming water plants grown in contaminated water
• Travelling to or living in regions where liver flukes are common, such as parts of Asia, Africa, Eastern Europe, and South America
• Being an immigrant from a country with high liver fluke prevalence

Where are liver flukes found?

Liver flukes are parasitic flatworms primarily found in developing regions with abundant freshwater habitats, where consuming raw or undercooked fish is common.

• High-risk areas include parts of Southeast Asia, particularly Thailand, Laos, Vietnam, and Cambodia, where infection rates may exceed 70%.
• Additionally, southern China and the Korean Peninsula are significant regions for liver fluke exposure.
• In Africa, the Nile Delta region of Egypt is known for liver fluke cases, while in South America, countries like Peru, Ecuador, and Brazil are also affected.
• Eastern Europe, including Russia and Ukraine, reports cases as well.

Liver fluke symptoms can range from mild abdominal pain to severe liver complications, with liver fluke treatment typically involving specific anti-parasitic medications guided by local health recommendations for those in high-risk areas.

What are the complications of liver flukes?

Without treatment, chronic liver fluke leads to progressive liver damage and biliary obstruction. Complications may include:

• Recurrent cholangitis (bile duct infection)
• Gallstones and cholecystitis
• Intrahepatic stones
• Liver abscesses
• Cirrhosis and liver failure
• Cholangiocarcinoma (bile duct cancer)

Studies show that infection with Opisthorchis species increases the risk of bile duct cancer by 15 times. It's estimated that liver fluke causes over 5000 cases of cholangiocarcinoma per year in Southeast Asia alone.

How are liver flukes diagnosed?

Diagnosing liver fluke usually involves:

• Stool tests to detect fluke eggs (repeated samples may be needed)
• Blood tests for antibodies to the parasite
• Imaging tests like ultrasound or CT scan to visualise the bile ducts
• Endoscopic retrograde cholangiopancreatography (ERCP) to examine the biliary system directly

Your doctor will also ask about your travel history, dietary habits and exposure to untreated water. Because liver fluke symptoms can mimic other digestive diseases, a high index of suspicion is needed to make the diagnosis.

How do we get rid of liver flukes?

Liver fluke treatment typically involves oral medications that kill the adult flukes:

• Treatment varies by fluke species, with different dosages and durations.
• In advanced cases with bile duct blockage, surgery may be necessary.
• Antispasmodic drugs can help relieve abdominal pain.

To prevent reinfection, avoid eating raw freshwater fish and aquatic plants in areas where liver flukes are found.

Can we prevent liver fluke infections?

Yes, you can greatly reduce your risk of liver fluke by following these guidelines:

• Cook freshwater fish and shellfish thoroughly to at least 63°C for 15 seconds
• Freeze fish for 24 hours at -20°C to kill fluke larvae
• Avoid eating raw watercress or aquatic plants, especially in endemic areas
• Don't drink untreated water from lakes, ponds or streams
• Wash hands with soap and water after using the toilet and before handling food
• When travelling, drink only bottled or boiled water and avoid street food

Health authorities recommend screening and treating high-risk populations to control liver fluke transmission. Improving sanitation and hygiene is also crucial to stop eggs from reaching snail habitats.

What can we expect if we have a liver fluke infection?

With prompt treatment, the outlook for liver fluke is generally good. Most people respond well to a single dose of medication, and symptoms resolve within a few weeks. However, chronic infections that have caused significant liver damage may require long-term monitoring and management of complications.

When to see a doctor?

See your doctor if you have unexplained digestive symptoms that persist for more than a few days, especially if you live in or have travelled to an area where liver flukes are prevalent. Fever, jaundice, severe abdominal pain or signs of bile duct obstruction warrant immediate medical attention.

Are liver flukes common in humans?

Liver flukes infect over 40 million people globally, with the highest rates in Southeast Asia and some South American countries. Worldwide, C. sinensis affects 35 million people, while 10 million have O. viverrini. Fasciola liver flukes infect 2.4-17 million individuals. Although less frequent in developed nations, liver flukes remain a significant health concern for millions worldwide.

Why is it called a liver fluke?

The term "fluke" comes from the Old English "floc", meaning flatfish. Liver flukes are called flukes because they are flattened, leaf-shaped worms resembling small fish. The word "fluke" is also used more generally for any parasitic flatworm or trematode. "Liver fluke" specifically refers to those species that infest the liver and biliary system.

Conclusion

Liver flukes may be tiny, but their impact on health can be profound. By understanding how these parasites spread, recognising liver fluke symptoms, and taking precautions with food and water, you can safeguard yourself and your loved ones.

At Metropolis Healthcare, we offer comprehensive diagnostic services to detect liver fluke infections through stool examination and blood tests. Our skilled technicians can collect samples from the comfort of your home, with reports delivered online. Take charge of your liver health today – book a test with Metropolis and get the answers you need.