Schistosomiasis (Bilharzia)

Schistosomiasis or bilharzia is a tropical disease caused by flukes (trematodes). The main distribution areas of the worm larvae are the inland waters of the tropical and subtropical areas of Africa, South and Central America and Asia.

Schistosomiasis (Bilharzia)

What is schistosomiasis?

The worm disease schistosomiasis can affect both humans and animals. It is estimated that around 200 million people worldwide suffer from schistosomiasis. There are four different Schistosoma pathogens that can cause schistosomiasis of the urinary tract, the intestine or the liver. See bittranslators for About Faecal Impaction.

For their development as an intermediate host, the schistosomes need a specific freshwater snail, in which they go through various stages of development from the egg to the tail larva.

The pathogen was discovered in 1852 by the German doctor Theodor Bilharz, after which the disease was named. Schistosomiasis causes acute and chronic symptoms, including serious organ damage. Left untreated, the disease can lead to death. With timely treatment with wormers, there are good chances of recovery.


Humans and animals infected with schistosomiasis shed trematode eggs in stool and urine. If the excretions get into surface water, the eggs are ingested by freshwater snails (intermediate host), in which they develop into larvae within a few weeks before being excreted again.

In the tail larva stage, they swim in inland waters and, upon contact, attach themselves to the skin of humans and animals (final host). The larvae then penetrate the human body through the skin and the cycle begins again.

Causes of the widespread occurrence of schistosomiasis are poor hygienic conditions of sanitary and water treatment facilities in the affected areas.

Symptoms, Ailments & Signs

The first sign of schistosomiasis is usually an itchy rash that appears a few days after the larvae penetrate the skin. About three to ten weeks later, the second phase of the disease begins with chills, fever, headache, muscle and body aches, swelling of the lymph nodes, liver and spleen are also possible.

Occasionally, this so-called Katayama syndrome can be life-threatening, but in many cases the affected person does not feel any significant symptoms even in this second phase. If left untreated, the disease goes into a third phase after several weeks, which is known as chronic schistosomiasis. The symptoms depend on which organs are affected by the schistosomes: mild cases of intestinal schistosomiasis are manifested by abdominal pain, a general feeling of illness and unwanted weight loss, bloody-slimy diarrhea suggests intestinal inflammation.

Blood in the urine, often associated with an increased urge to urinate and a burning sensation when urinating, can indicate involvement of the urinary and genital organs. In the worst case, damage to the bladder mucosa can result in bladder cancer. If worm eggs get into the portal vein system of the liver, internal bleeding is sometimes the result. A functional disorder of the liver can lead to an accumulation of water in the abdominal cavity (ascites) in the advanced stage. Occasionally, involvement of the nervous system causes neurological deficits and convulsions.

Diagnosis & History

The incubation period for schistosomiasis is between three and ten weeks from the time the larvae penetrate until the first signs of the disease develop. The tail larvae have special adhesive organs with which they adhere to the skin of the definitive host.

After attaching to the skin, the larvae manage to penetrate the skin and underlying tissue layers within a few minutes. The intrusion itself is usually not noticed. Sometimes small itchy spots form at the point of entry due to the secreted enzyme of the larvae, but these soon disappear again.

Once in the definitive host’s blood and lymphatic system, they reach the liver, where they develop into sexually mature flukes within a few weeks. In this phase, various symptoms such as fever, abdominal pain, headache and body aches occur. Swollen lymph nodes, liver and spleen are often palpable.

The released eggs travel through the bloodstream to other organs (bladder, intestines, lungs, kidneys, and central nervous system), where they cause inflammation that makes the disease chronic.

The diagnosis of schistosomiasis is relatively simple. As soon as the trematodes begin to lay eggs, they are microscopically visible in the final host’s excrement. The immune system forms antibodies that can also be detected in the blood. If the disease has already manifested itself, the eggs of the trematodes can also be detected by biopsies of affected organs such as the intestinal mucosa, bladder wall or liver.


If there is insufficient or no treatment, various complications can occur in the course of schistosomiasis. If the initial fever rises above 41 degrees Celsius, this can lead to serious circulatory problems. There is an acute danger to life for children, the elderly and the sick. If left untreated, schistosomiasis develops into a chronic infection.

Depending on where the worms lay their eggs, different symptoms can occur. Liver involvement can lead to the formation of varicose veins in the esophagus. The formation of fistulas in the intestine and bladder is conceivable. This can be accompanied by watery or bloody diarrhea, which carries the risk of dehydration or anemia.

In addition, in the acute phase of the disease, the intestine is extremely susceptible to other pathogens and tends to form mucosal proliferation. Malignant degeneration of the bladder is also possible and subsequently leads to bladder cancer. If the course is particularly unfavorable, schistosomiasis ends with the death of the patient. Therapy of schistosomiasis can also cause adverse events. Occasionally, dizziness, hives or gastrointestinal problems occur. Some patients are also allergic to the drugs used.

When should you go to the doctor?

Schistosomiasis should always be treated by a doctor. It cannot heal itself, so that a doctor must be consulted in any case in order to treat the schistosomiasis properly. In the worst case, the victim can die. A doctor must be consulted if the person concerned suffers from a severe rash on the skin combined with itching.

Usually, this rash occurs without any particular reason and has a very negative effect on the quality of life of the affected person. There is also severe pain in the limbs and, in most cases, swollen lymph nodes. Swelling of the spleen or liver also often indicates schistosomiasis.

First and foremost, a general practitioner can be consulted. In emergencies or acute symptoms, the hospital can also be visited or an ambulance can be called. The life expectancy of those affected may also be reduced as a result of this disease.

Treatment & Therapy

The treatment of the acute phase of schistosomiasis is based on two pillars. On the one hand, the acute symptoms are treated with antipyretic and painkilling medication. Furthermore, special anthelmintics such as praziquantel are administered to kill the trematodes and worm eggs.

The success of the therapy depends above all on how severe the extent of the worm infestation is and whether the disease has already entered the chronic phase. Schistosomiasis is also associated with an increased incidence of bladder cancer, pneumonia and liver cirrhosis in the infected areas.


Since no medicinal prophylaxis against schistosomiasis pathogens is available to date, infection can only be prevented by preventive measures. When traveling to areas contaminated with the schistosomiasis pathogen, any contact with inland waterways should be avoided.

This applies above all to swimming and diving in lakes and rivers in the relevant regions. Infection can also occur with drinking water if it is contaminated with trematode eggs. For this reason, you should never drink tap water that has not been boiled beforehand. A vaccine has been developed against one of the four subtypes of schistosomiasis pathogens, but it is still in the testing phase.


After treatment of the schistosomiasis (bilharzia) with antipyretics, painkillers and possibly special drugs to kill trematodes, the organism needs a recovery phase to rest. Patients should follow the doctor’s advice closely, especially if the worm infestation was quite severe and the disease has become chronic. There are currently no preventive medications available to prevent infection.

It is all the more important to take some security measures. Those affected should see a doctor as soon as possible if there are signs. Self-help measures replace neither treatment nor comprehensive aftercare. Even if patients are on the mend, they should keep an eye on their symptoms in case further medical intervention is necessary. Depending on the general condition, the pathogens can cause dangerous organ damage.

This is particularly risky for people who already suffer from a previous illness. With the necessary attention and caution, any problems will be noticed at an early stage. Then a short-term doctor’s appointment must be arranged in order to examine the condition of those affected in detail. Subsequent medical advice helps patients to recover and strengthen their organism. However, the body needs a certain amount of time to fully recover.

You can do that yourself

Before a stay abroad, the traveler should find out about the local and hygienic conditions of his travel destination sufficiently and in good time. Tour operators or the Foreign Office can answer open questions about the conditions abroad and help to clarify possible health conditions at the desired place of stay.

Since the disease is widespread in tropical or subtropical areas, it should be discussed with the general practitioner before departure whether possible vaccinations should be carried out or whether the person concerned should take precautions to support their own organism. Although there is no vaccination for this disease in particular, it is still necessary to check whether the general condition needs to be protected against other germs. The schistosomiasis pathogen can cause serious and life-threatening organ damage. Therefore, people who suffer from organic pre-existing conditions are particularly at risk. You are advised to discuss the travel plans and any circumstances of the trip in detail in close cooperation with the doctor treating you.

At the first signs of physical problems, a doctor’s visit is essential, since self-help measures are only sufficient to provide information about possible circumstances and risks. They cannot replace treatment or relieve existing symptoms. At the first irregularities, a doctor must be consulted, as there is an acute need for action.