Opistorchiasis, infection with sucking worms

Opistorchiasis is an infectious disease caused by flukes. Sucker worms are flatworms that live on a host. Contamination occurs through undercooked food. The disease mainly occurs in the Far East. People who go on holiday to Asia or China, among others, are more likely to contract this disease. However, it sometimes also occurs in the Netherlands and Belgium. What are the symptoms?


Sucker worms of the genus Opistorchis are responsible for the disease Opistorchiasis. These are parasitic flatworms. A parasite is an organism that lives off its host. A flatworm is characterized by an elongated and flat body. Opistorchis is a liver fluke. This means that they live in the liver of their host. They move through the blood and the eggs of these worms are excreted through the urine or feces.

Infectious disease

The disease opistorchiasis is an infectious disease: the patient becomes infected with the worm through contaminated food. This mainly concerns fish and rarely meat. Ruminants, sheep or fish can be infected with the flatworm. If the meat or fish is not heated sufficiently or is eaten raw, the larvae are not killed. In this way, the infection enters through the mouth.

Life cycle

This flatworm has a complicated life cycle. The host will excrete eggs through feces or urine. When the right (freshwater) snail finds and eats the eggs, the eggs hatch within the snail. The eggs that end up in the water can also hatch, after which the larvae enter a suitable snail. The larvae leave the snail and end up in a fish by penetrating through the skin, where they develop further.


It is estimated that more than 50 million people are infected with this infectious disease. The majority come from Asia, where a lot of raw fish is eaten. Often no symptoms occur at all, meaning that the majority of infections go unnoticed. In some cases, abdominal pain occurs accompanied by diarrhea or constipation. This can also alternate. Sometimes the eggs are visible in the stool. In severe cases, reduced functioning of the liver or bile ducts may occur. Liver disease is characterized by pain in the upper abdomen (right), nausea, weight loss, fever and/or jaundice. In countries where the disease is common, there has also been an increase in the number of patients with liver cancer. The disease opistorchiasis is probably related to this.

Netherlands, Belgium and other countries

The disease is very rare in the Netherlands and Belgium. If it is found in a patient, it is often an imported infection. The disease is then contracted during a holiday or stay in another country. Places where the disease is common include Thailand, Cambodia and other Southeast Asia. A lot of raw fish is eaten in these places. The infection can be prevented by not eating raw fish and choosing well-done fish. If this is not possible, it is better not to eat fish at all. You should also be careful when eating raw or undercooked meat. Fish and meat are sometimes prepared together, resulting in cross-contamination. This means that contaminated fish can ultimately also contaminate uncontaminated meat due to unhygienic work. The hygiene and quality requirements in these types of countries are much lower than in the Netherlands or Belgium. In Europe, fish is generally much less contaminated with parasites. On the one hand, this has to do with the living environment, and on the other hand, with quality requirements and better food preparation. More fish is also farmed here for consumption. Farmed fish is more often free of parasites. In the Netherlands, herringworm disease is more common due to eating raw herring.


Many infections go unnoticed because no complaints arise. The infection will eventually disappear. Sometimes the infection remains for a long time or is serious. In these cases, symptoms do occur. These are often confused with a stomach flu or food poisoning. The doctor can check the stool for the presence of eggs of the genus Opistorchis. The stool must be collected and sent to a laboratory. there it is viewed under the microscope. A definitive answer can be given quite quickly. In case of infection, an anti-worm medication is administered that kills the worms. The disease will disappear quickly, sometimes the wormer is not sufficient and the patient remains ill. A drug will then be prescribed again. If it appears that the liver is not functioning sufficiently, this will be treated. In severe cases, liver cancer is the result. This form of cancer also occurs in our own countries, but is never actually the result of this infectious disease. In the Far East we see liver cancer occurring much more often after an infection with flatworms.

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