The Link Between Liver Flukes and Bile Duct Cancer

If you were to find out that more than 35 million people are infected with liver fluke, wouldn’t you be worried that you’re one of them? What makes it even scarier is that these parasites can live inside our bodies for as long as 20 to 30 years before manifesting through various symptoms. Even if you are one of the lucky ones whose infection is asymptomatic, isn’t it unsettling to know that wrigglers are living inside you that may cause you pain and sickness any minute? At times, liver flukes can even cause terminal diseases at their late stages. That is what happened to some US Vietnam war veterans who have been diagnosed with liver flukes and are now suffering from cholangiocarcinoma or bile duct cancer.

A blood testing conducted among Vietnam war veterans by the US Department of Veterans Affairs (VA) found out that more than 20% of the veterans tested are positive for antibodies against liver flukes. This type of liver fluke epidemic is even more common in Asian countries. In 2001, for example, a 9.4% prevalence was reported in Thailand, which means that over 6 million people were infected at that time. In Vietname, it is estimated that 75% of the population are infected with liver flukes.

In the case of the US veterans, it is alarming that about 700 Vietnam veterans have suffered from bile duct cancer in the past 15 years. This type of cancer is supposedly rare in developed and western countries, with only seven casualties for every 1 million people. As many as 8,000 people are diagnosed with bile duct cancer yearly in the US alone. Among the diagnosed cases, a few are caused by liver flukes.

What are liver flukes?

As adults, liver flukes are flat, leaf-like parasites measuring 8-10 mm. That’s 5/16 to 3/8 of an inch. They cause inflammation and dilation of the bile ducts and also thickening of the bile duct walls. Flukes can be ingested through the consumption of fluke-infested, uncooked fish, watercress, or other freshwater animals (like snails, frogs, and mussels). Infection can also be initiated if water contaminated by cattle or sheep excrements will be used for cooking or drinking. Liver flukes may be found globally, but they are most common in Asia and Eastern Europe. 

There are three most well-known species of liver flukes that cause human infection. These are Clonorchis sinensisOpisthorchis viverrini, and Opisthorchis felineus, causing clonorchiasis and opisthorchiasis. Infections are often diagnosed through complete blood count (CBC) tests and checking antibody levels for the parasite. Stool examination and imaging tests like ultrasound, CT scan, MRI, and ERCP may be done.

Oftentimes, liver fluke infection is asymptomatic and some people can live full lives despite the existing parasitic infestation. In others, symptoms manifest, including abdominal pain, nausea, fever, diarrhea, hives, and loss of appetite. Jaundice may also occur if the sheer multitude of flukes in the bile ducts is already blocking the bile flow.

Liver flukes cause several complications:

1. Recurrent Pyogenic Cholangitis – Acute suppurative (i.e., pus-producing) cholangitis (inflammation of the bile ducts) may happen when the bile ducts are blocked by masses of dead worms, ova, and mucin. This condition can be aggravated by the decreased bile flow caused by parasites’ abundance and excretion.

2. Gallstone and Bile Duct Stone Formation – Bile duct stones can be the consequence of bile stagnation due to the obstruction of the ducts. Bilirubin stones can also form as the bilirubin undergoes mechanical and chemical changes during cholangitis (bile duct inflammation).

3. Cholangiohepatitis – inflammation of the liver and bile ducts

4. Fluke infection in various body parts such as the brain, the liver, lymph nodes, skin, or spinal cord.

5. Gallbladder perforation

6. Pancreatitis

7. Bile Duct Cancer

Bile Duct Cancer

Bile duct cancer or cholangiocarcinoma is a rare type of cancer that affects the biliary system. It is commonly associated with Clonorchis sinensis and Opisthorchis viverrini. Bile duct cancer is considered very difficult to diagnose and treat due to its wide variation and the condition’s rarity. It also usually presents in its late stages, increasing mortality risk.

Three types of Cholangiocarcinoma

  • Intrahepatic – which forms in the bile ducts within the liver
  • Extrahepatic – also called distal bile duct cancer
  • Perihilar bile duct cancer – forms at the point where the hepatic ducts join together to exit the liver

Symptoms of Bile Duct Cancer (Cholangiocarcinoma)

  • Jaundice
  • Pale stools
  • Dark urine
  • Pruritus
  • Malaise
  • Nausea and vomiting
  • Abdominal pain
  • Weight loss
  • Other symptoms depend on the infection type, location of the tumor, and the susceptibility of the individual

Other risk factors for bile duct cancer include the following:

  • Chronic ulcerative colitis
  • Primary sclerosing cholangitis or PSC
  • Cysts in the bile ducts
  • Cirrhosis of the liver
  • Hepatitis B or C virus
  • Diabetes
  • Obesity
  • Genetic factors

Liver Flukes and Bile Duct Cancer

There are various ways liver fluke infection can escalate to bile duct cancer. One is through mechanical injury from the feeding and migration of the flukes combined with the excrement. The tissue damage and scarring caused by the suckers of the fluke hook and its other activities can lead to bile duct cancer. Secondly, persistent inflammation and prolonged infection with liver fluke may contribute to the development of cholangiocarcinoma. The liver flukes can also induce biliary cell damage through the actions of oxygen radicals causing oxidative DNA damage to the biliary system.

 

Liver Fluke Prevention

Liver flukes are not prevalent in developed countries, but it is still better to be safe than sorry. Prevention is critical, especially while traveling or consuming unfamiliar food.

Since C. sinensis and O. viverrini are acquired through ingestion, ensure that your drinking water is treated or boiled, especially when traveling in the countryside. If uncertain, it is better to purchase sealed distilled water bottles that guarantee your safety. Aside from being wary of the liquids you intake, it is important to be cautious about the food you eat. Even vegetables grown and drawn near infested areas can be carriers.

It is always best if you cook your food at home. But at times when you can’t, avoid consuming raw food, especially animal liver and fish. Also, choose reputable eating places to be confident about their food handling and safety during preparation and serving. And on the topic of cleanliness, washing your hands with soap and clean water always goes a long way.

Liver Flukes Diagnosis and Treatment

So what do you do if you already are infected with liver fluke? Nothing beats regular consultation with a medical practitioner. With that, you can have the peace of mind that your condition is being monitored. The infection is not fatal, but complications arising from it can be. So upon discussion with your doctor, you may be given the following treatment options:

1. Medication – Some pharmaceutical drugs such as triclabendazole, praziquantel and tribendimidine may be prescribed for 2-7 days, depending on the dosage. After the medication, stool examination will be repeated, and patients will be recommended for retreatment if an infection is still present.

2. Alternative treatment – There are a few alternative treatments for those suffering from liver flukes. Examples are colonic irrigation, parasite cleanses, goldenseal, natural liver fluke detox formulas, bowel cleaners such as Premier Cleanse, and bile movers like  Beet Capsules. A word of caution though, it is best to consult your doctor before taking any supplements or doing these treatments to make sure that it does not counteract any medications you are taking or that it will not worsen any other physical condition you may have.

3. Paratosin  – This botanical blend provides gastrointestinal and immune support for patients with liver fluke and other related parasitic infections.

4.BiliVen  – BiliVen is purported to expand the bile ducts to allow for the easier exit of the flukes and offer general gallbladder and bile support.

 

References: 

American Cancer Society (2016) What Are the Risk Factors for Bile Duct Cancer?

Chan, C. W., & Lam, S. K. (1987). 5 Diseases caused by liver flukes and cholangiocarcinoma. Bailliere’s clinical gastroenterology1(2), 297-318.

Fox News (2017) VA study shows parasite from Vietnam may be killing vets.

Khan, S. A., Thomas, H. C., Davidson, B. R., & Taylor-Robinson, S. D. (2005). Cholangiocarcinoma. The Lancet, 366(9493), 1303-1314.

Kim, T. S., Pak, J. H., Kim, J. B., & Bahk, Y. Y. (2016). Clonorchis sinensis, an oriental liver fluke, as a human biological agent of cholangiocarcinoma: a brief review. BMB reports49(11), 590.

Lim, J. H. (2011). Liver flukes: the malady neglected. Korean journal of radiology12(3), 269-279.

Sithithaworn, P., Haswell-Elkins, M. R., Mairiang, P., Satarug, S., Mairiang, E., Vatanasapt, V., & Elkins, D. B. (1994). Parasite-associated morbidity: liver fluke infection and bile duct cancer in northeast Thailand. International journal for parasitology24(6), 833-843.

Sripa, B., & Pairojkul, C. (2008). Cholangiocarcinoma: lessons from Thailand. Current opinion in gastroenterology, 24(3), 349.

Sripa, B., Brindley, P. J., Mulvenna, J., Laha, T., Smout, M. J., Mairiang, E., … & Loukas, A. (2012). The tumorigenic liver fluke Opisthorchis viverrini–multiple pathways to cancer. Trends in parasitology28(10), 395-407.

Sripa, B., Kaewkes, S., Sithithaworn, P., Mairiang, E., Laha, T., Smout, M., … & Bethony, J. M. (2007). Liver fluke induces cholangiocarcinoma. PLoS medicine, 4(7), e201.

US Department of Veterans Affairs (2017) Bile Duct Cancer (Cholangiocarcinoma) and Liver Fluke Infection.

Watanapa, P. (2002) Liver fluke-associated cholangiocarcinoma. British Journal of Surgery. Volume 89, Issue 8. Pages 962–970.