In the Western world, we rarely think about parasitic creatures living inside us. Surely such a thing doesn’t happen in our modern society? Except it can and does. There are many types of parasitic worms out there, and they cause illness in millions of people worldwide. Every so often, we hear stories of people who have experienced severe illness due to microscopic organisms that have somehow burrowed into the human body and set up residence. One of these parasites is the humble liver fluke.
You may not have heard of flukes before—or maybe you have, in a high school biology classroom. However, they are usually not the first thing we think of when it comes to stomach discomfort. Do you know enough about flukes to see the signs and prevent permanent liver damage?
What Is a Liver Fluke?
A liver fluke is a parasitic flatworm, commonly found in Southeast Asia. The most common types of flukes are Clonorchis sinensis, Opisthorchis viverrini and Opisthorchis felineus.
Humans usually become infected with liver flukes after eating raw or undercooked freshwater fish and in some cases watercress. Once the liver flukes have been ingested, they travel from the intestines to the bile ducts in the liver (hence the name). About four to six months after settling in the bile ducts, an adult fluke can begin producing eggs, which are passed into the intestines and then excreted in the feces. One adult fluke can lay between 2000 and 4000 eggs in a day. The parasites can live in the bile ducts for a long time—sometimes as long as 20 or 30 years!
Approximately 35 million people worldwide are infected with liver flukes. While they are not common in the United States, they are most commonly found in Southeast Asian countries like China, Vietnam, Taiwan, South Korea, and Laos. People living along rivers may be prone to fluke infection due to a habit of eating raw or undercooked freshwater fish.
Even if you do not live in an area where flukes are common, you could still become infected if you eat undercooked freshwater fish. Your chances of contracting flukes also go up if you travel to places where it is more common.
Liver flukes are not contagious between humans. You cannot catch liver flukes by interacting with someone who has been infected.
Most people who are infected with liver flukes may not even know. Although flukes can cause long-lasting inflammation of the bile ducts, in many cases people may not show symptoms that are easily recognized. However, there are a few symptoms you can keep an eye out for:
In some cases, symptoms of liver fluke infection can be mistaken for stomach ailments such as irritable bowel syndrome.
Chronic liver fluke infection, even if there are no symptoms, can cause serious damage to the liver, such as cirrhosis. Severe infection can also cause an enlarged liver or jaundice (yellowing of the skin or eyes) due to the obstruction of the bile ducts.
While not every person who is infected with flukes may show symptoms, there are complications that can occur. Rare complications include stone formation, infections of the biliary system (bile ducts), and cholangiocarcinoma (bile duct cancer).
If you live in areas where liver flukes are common, you may want to have screening tests on a regular or semi-regular basis. If you have recently traveled to a part of the world where flukes are common, you also should be screened as a precaution.
Common screenings tests include stool ova tests, where a person's stool is checked for fluke eggs, and liver ultrasound scans or computed tomography (CAT) scans. Ultrasound or CAT scan images may show dilation of the bile ducts, which can indicate flukes.
Your healthcare professional may recommend additional tests to confirm a diagnosis of liver flukes. A full blood count can indicate the elevation of a particular type of white blood cell called eosinophils. Some immunological techniques, which test the blood or stool for worm-specific antibodies or antigens, can also detect flukes. However, these immunological tests do not give evidence of whether the infection is current, recent, or occurred a long time ago.
Treatment and Prevention
Once your doctor has confirmed a diagnosis of liver flukes, you’ll want to discuss your treatment options. Most of the time, flukes are successfully treated with medication, but there are a few other options you may consider.
Liver flukes can be completely cleared through treatment with medication. However, it can take a long time depending on how many flukes are in the liver. In some cases, people report passing several hundred flukes a day in their stool during treatment to eradicate the parasites.
There are several medications available to treat flukes, known as antihelmintic medications. They go by several names, but two that are commonly used are praziquantel and triclabendazole. There is research showing that tribendimidine is highly effective in treating flukes as well. Triclabendazole is specifically recommended by the World Health Organization for the treatment of flukes.
Older drugs such as artemether, artesunate, and mefloquine, while effective, are not as effective as the newer medications, and are not recommended.
If the infection is caught too late, then sometimes the damaged tissue in the liver must be surgically removed. The sooner the flukes are found and treated, the less harm they can do to the liver and bile ducts.
During treatment, as the flukes die, they detach from the liver and are passed out of the body through the stool. If you are experiencing symptoms, you may notice that your symptoms clear up as the flukes pass from your system. The only sure way to tell if you are fluke-free is to visit your doctor, who can run tests to verify whether there are fluke eggs present in your stool.
Over time, parasites can grow accustomed to the drugs, and become resistant to treatment, which is why it is important to continue research to develop new drugs and treatments to combat flukes.
While medication is the most effective treatment, there are alternative treatments you can try. Some people recommend taking the herb goldenseal for parasitic infections. Others have reported positive effects after undergoing colonic irrigation and parasite cleanses.
If you are looking for relief from the symptoms, such as fever or abdominal pain, you can take over-the-counter pain relievers such as acetaminophen (Tylenol). If you are suffering from nausea and vomiting, you can try anti-nausea medication.
However, it is important to note that if you are only treating the symptoms, you are not treating the underlying cause. It is a better and more effective cause of action to treat the actual fluke infection to avoid further complications and continued symptoms.
People who are infected with liver flukes generally have a good prognosis, especially if the parasites are caught early. Flukes by themselves are not fatal. However, they may cause serious complications that, if left untreated, can cause further infections and possibly contribute to cancer. People with flukes may also experience discomfort from inflammation in the bile ducts, but many people live years without experiencing any symptoms at all. If symptoms do occur, they are treatable. As with many conditions, early detection is important for the best outcome and prevention of complications.
The potential complications of liver flukes are perhaps the most problematic part of the infection, but even mild complications are treatable. Cholangiocarcinoma is the most severe complication that can arise as a result of liver flukes although it is rare. If caught early, the five-year survival rate of this particular cancer ranges between 20 and 50%.
Luckily, liver flukes are easily prevented with thorough cooking and sanitation. Ensure that any freshwater fish or watercress you consume are thoroughly cooked before you eat them. If you are traveling to an area where flukes are common, or an area with poor sanitation, avoid consuming food and water that might be contaminated.
There is no vaccine to prevent liver fluke infections, so carefully watching what you eat and drink is the most effective way to make sure you avoid these parasites.
Liver flukes are uncommon in the Western world, but not impossible. If you consume raw or undercooked freshwater fish, you still have a chance of becoming infected. The best way to make sure you do not have liver flukes in your system is to make sure that your fish is always cooked properly.
If you have a fluke infection, it is important to catch it early. If you live or travel to areas where flukes are common, and you experience symptoms, consult your healthcare provider as soon as possible for a stool test. Early detection can help prevent complications that can have a serious negative impact on your health.
With more research, it is possible we will see a vaccine for flukes in the future. Until then, focusing on prevention is your best bet.