Schistosomiasis or bilharzia is a tropical disease caused by sucking worms (trematodes). The main areas of distribution of the worm larvae are inland waters of tropical and subtropical Africa, South and Central America, and Asia.
What is schistosomiasis?
The worm disease schistosomiasis can affect both humans and animals. Estimates have shown that approximately 200 million people worldwide suffer from schistosomiasis. There are four different Schistosoma pathogens that can cause schistosomiasis of the urinary tract, intestine, or liver. The schistosomes require a specific freshwater snail as an intermediate host for their development, in which they pass through various developmental stages from egg to tail larva. The pathogen was discovered in 1852 by the German physician Theodor Bilharz, after whom the disease was also named. Schistosomiasis causes acute and chronic symptoms and even serious organ damage. If left untreated, the disease can lead to death. With timely therapy with vermifuge, there is a good chance of cure.
Causes
Humans and animals infected with schistosomiasis excrete trematode eggs in feces and urine. If the excretions reach surface waters, the eggs are ingested by freshwater snails (intermediate host), in which they develop into larvae within a few weeks before being excreted. In the tail larvae stage, they swim in inland waters and attach to the skin of humans and animals on contact (final host). The larvae then enter the human body through the skin and the cycle begins again. Causes for the widespread occurrence of schistosomiasis are poor hygienic conditions of sanitation and water treatment facilities in affected areas.
Symptoms, complaints, and signs
The first sign of schistosomiasis is usually a rash accompanied by itching, which 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 limb pain, and swelling of the lymph nodes, liver and spleen is also possible. Occasionally, this so-called Katayama syndrome can be life-threatening, but in many cases the affected person does not experience any significant symptoms even in this second phase. If left untreated, the disease progresses to 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 bilharzia are noticeable by abdominal pain, general feeling of illness and unwanted weight loss; bloody-mucous diarrhea suggests intestinal inflammation. Blood in the urine, often associated with an increased urge to urinate and burning during urination, may 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, and liver dysfunction can lead to accumulation of water in the abdomen (ascites) in advanced stages. Occasionally, an attack on the nervous system causes neurological deficits and convulsions.
Diagnosis and progression
The incubation period for schistosomiasis is between three and ten weeks from larval entry to development of the first signs of disease. The tail larvae have special adhesive organs with which they adhere to the skin of the end hosts. After skin attachment, the larvae succeed in penetrating the skin and the underlying tissue layers within a few minutes. The penetration itself is usually not noticed. Sometimes small itchy spots form at the site of entry due to the enzyme secreted by the larvae, but these soon disappear. Once in the blood and lymph circulation of the final host, they enter the liver, where they develop into sexually mature sucker worms in a few weeks. During this stage, various symptoms occur, such as fever, abdominal pain, headache and pain in the limbs. Swollen lymph nodes, liver and spleen are often palpable as well. The secreted eggs travel through the bloodstream to other organs (urinary bladder, intestines, lungs, kidneys, and central nervous system), where they cause inflammation that makes the disease chronic.Diagnosis of schistosomiasis is relatively simple. As soon as the trematodes begin to lay eggs, these are microscopically visible in the excretions of the end host. The immune system produces antibodies that are also detectable in the blood. If the disease has already manifested, trematode eggs can also be detected by biopsies of affected organs such as the intestinal mucosa, bladder wall or liver.
Complications
If treatment is inadequate or absent, various complications can occur during the course of schistosomiasis. If the initial fever rises above 41 degrees Celsius, serious circulatory problems may result. In children, the elderly and the sick, there is an acute danger to life. If left untreated, schistosomiasis develops into a chronic infection. Depending on where the worms lay their eggs, different symptoms may occur. An infestation of the liver can lead to the formation of varicose veins in the esophagus. On the intestine and bladder, the development of fistulas is conceivable. Accompanying this may be watery or bloody diarrhea, which carries the risk of dehydration or anemia. In addition, during the acute phase of the disease, the intestine is extremely susceptible to other pathogens and tends to develop mucosal growths. Malignant degeneration of the bladder is also possible and subsequently leads to bladder cancer. In a particularly unfavorable course, schistosomiasis ends with the death of the patient. Therapy for schistosomiasis can also cause adverse events. Occasionally, dizziness, hives or gastrointestinal complaints occur. Some patients also have allergic reactions to the drugs used.
When should you see a doctor?
Schistosomiasis should always be treated by a doctor. There can be no self-healing in the process, so a doctor must be consulted in every case to properly treat schistosomiasis. In the worst case, it can lead to the death of the affected person. A doctor must be consulted if the affected person suffers from a severe rash on the skin associated with itching. As a rule, 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 very severe pain in the limbs and, in most cases, swollen lymph nodes. Likewise, swelling of the spleen or liver often indicate schistosomiasis. In the first instance, a general practitioner can be consulted. In emergencies or acute symptoms, the hospital can also be visited or an emergency doctor called. Possibly, the life expectancy of the affected person is also reduced by this disease.
Treatment and therapy
Treatment of the acute phase in schistosomiasis is based on two pillars. First, the acute signs of the disease are treated with antipyretic and analgesic drugs. Furthermore, special worming agents such as praziquantel are administered to kill the trematodes and worm eggs. The success of the therapy depends mainly on the severity of the worm infestation and whether the disease has already entered the chronic phase. Schistosomiasis is also associated with a clustered incidence of bladder cancer, pneumonia, and liver cirrhosis in infested areas.
Prevention
Because no drug prophylaxis against the schistosomiasis pathogen is available to date, infection can only be prevented by taking preventive measures. When traveling to areas contaminated with the schistosomiasis pathogen, all contact with inland waters should be avoided. This applies in particular to swimming and diving in lakes and rivers in the corresponding regions. Infection can also occur with drinking water if it is contaminated with trematode eggs. Therefore, tap water should not be drunk unless it has been boiled beforehand. A vaccine has been developed against one of the four subtypes of the schistosomiasis pathogens, but it is still in the testing phase.
Follow-up
After therapy for schistosomiasis (bilharzia) with antipyretics, analgesics, and possibly special drugs to kill trematodes, the organism needs a recovery period to rest. Patients should follow the doctor’s advice carefully, especially if the worm infestation was quite severe and it has become a chronic disease. At present, there are no preventive medications against the infection.This makes it all the more important to take some safety measures. Those affected should see a doctor early on if they notice any signs. Self-help measures are no substitute for treatment or comprehensive follow-up care. Even if patients are on the road to recovery, they should keep an eye on their symptoms in case renewed medical intervention is necessary. Depending on the general condition, the pathogens can cause dangerous organ damage. This is especially risky for those already suffering from a pre-existing condition. With the necessary attention and caution, any problems will be noticed at an early stage. Then a short-term doctor’s appointment should be arranged to examine the condition of the affected person in detail. The subsequent medical advice will help the patients to recover and strengthen the organism again. However, the body needs some time to recover completely.
This is what you can do yourself
Before a stay abroad, the traveler should always inform himself sufficiently and in time about the local and hygienic conditions of his destination. Tour operators or the foreign office can answer open questions about the conditions abroad and help clarify possible health conditions of the desired place of stay. Since the disease is widespread in tropical or subtropical areas, it should be discussed with the attending general practitioner before the start of the journey whether possible vaccinations should be carried out or the person affected should take precautions to support his own organism. Although there is no protective vaccination for this disease in particular, it should still be checked whether the general condition needs to be protected against other germs. The pathogen of schistosomiasis can cause serious and life-threatening organ damage. Therefore, people suffering from organic pre-existing diseases in particular belong to a risk group. They are advised to discuss travel plans and any circumstances of the trip in detail in close cooperation with their attending physician. At the first signs of physical complaints, a visit to the doctor is indispensable, as the self-help measures are only sufficient for the information of possible circumstances and risks. They cannot replace treatment or provide relief from existing symptoms. At the first irregularities, a physician must be consulted, as acute action is required.