Suction worms or Trematoda

Suction worms are flat worms that mainly occur in the (sub) tropics. They live in a moist environment. Sheep and cattle contamination is common in these areas. The intermediate host of the suction worm is a freshwater snail. Eating raw fish, aquatic plants such as watercress or swimming in contaminated water can cause humans to become infected with the suction worm. The suction worm causes diseases such as liver fluke, schistosomiasis and cercarian dermatitis.

Suction worms

Suction worms are also called Trematoda. These belong to the flatworms. The mouth opening with a suction worm is at the front. They have one or two suction cups. Parasitize worms. This means that they live from a host. Most suction worms enter the human body because the host eats aquatic plants, in particular watercress. Watercress is a plant that grows in more humid places and is offered as a vegetable. Eating raw freshwater fish can also cause suction worms.


Many sheep or cattle are infected with suction worms. The adult suction worm lays eggs, which come out with the faeces of the animal. The eggs are eaten mainly by the freshwater snail. From the snail comes the young stage of the suction worm, which forms cysts on aquatic plants. When humans eat these aquatic plants, they become infected with the suction worm. Within the body of the human host, the immature suction worm grows into an adult specimen. There they will produce eggs in organs.
Another way of contamination is by eating raw freshwater fish. Many freshwater fish are infected with the immature version of the suction worm. If fish is not heated sufficiently, the parasitic suction worms live and infect humans. Swimming in water in which the suction worm is located is also a source of contamination. The suction worm can penetrate the body through the skin.
The suction worm can live a long time. Suction worms are sometimes found that have been present in the body for 20 to 25 years. Suction worms continue to produce eggs during their stay in the host. This ensures the suction worm of the survival of its species.


Suction worms are not harmless. They cause diseases that can sometimes cause serious symptoms. They are sometimes deadly among cattle, not always in humans. Infection with suction worms is very difficult to combat. In addition, the infection and therefore the disease persist for many years. In countries where hygiene is poorer, these diseases are more common.

Liver fluke disease

This disease does not actually occur in the Netherlands. It is mainly used in countries such as Lebanon, Peru and Egypt. The cause of the liver fluke is the suction worm Fasciola hepatica. The adult liver bone is located in the bile ducts of the liver. There he produces eggs that come out through the faeces with the bile. When the environment is moist enough, larvae develop from the eggs and penetrate a water snail. There the larvae multiply into a different type of larvae. These leave the snail and attach themselves to aquatic plants. A host eats the aquatic plants, after which the larvae have entered the body. They pierce the intestinal wall in the intestines and look for the liver. They grow in the liver, after which they end up in the bile ducts to lay eggs there.
Symptoms of the liver-bone disease are: abdominal pain, nausea, fever and weight loss. Anemia sometimes develops with weak people. Treatment of the liver fluke disease consists of worm agents, which are often used for cattle. Fighting is very difficult. Good hygiene for prevention is therefore recommended.


Another disease caused by worms is schistosomiasis. This is caused by the suction worm schistosoma. The disease does not occur in the Netherlands, but is contracted in the (sub) tropics by coming into contact with contaminated fresh water. The adult suction worm lays eggs in the host, which end up in the water through the faeces or urine. In the water, larvae hatch from the eggs. These penetrate a freshwater snail. There they multiply and leave the snail like a different species of larvae. These larvae invade the skin of their final host.
Symptoms often only occur a few months after infection. However, blisters may develop on the skin after the larvae have entered the skin. The symptoms often resemble flu: fever, chills, muscle aches and cough. Later nausea, diarrhea, joint pain, abdominal pain, headache and weight loss develop. Often these symptoms resume after a few weeks. Then other complaints arise. Inflammation in the bladder or intestines is a common complaint. Depending on where the suction worm is located, organs are permanently damaged. Often that is the bladder, intestines, lungs or liver.
Treatment is also difficult now. When the suction worm is still alive as a larva, it is easier to treat. Damage caused to the organs will not be repaired automatically after treatment.

Cercarian dermatology

The cercarian dermatitis disorder is also caused by schistosoma and also occurs only in the (sub) tropics. The life cycle is therefore the same as contamination. The larvae penetrate the skin, causing itching. This is often noticeable within one hour after the invasion. Blisters appear on the skin, headache and fever. Most symptoms disappear after 1 to 3 weeks. This condition disappears again and is a reaction of the skin to the invasion of the larvae. It is also called swimmer's itch.

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