Symptoms

Many people with schistosomiasis do not have any symptoms, or do not experience any for several months or even years.

You probably would not notice that you have been infected, although occasionally people get small, itchy red bumps on their skin for a few days where the worms burrowed in.

After a few weeks, some people develop:

• a high temperature (fever) above 38C
• an itchy, red, blotchy and raised rash
• a cough
• diarrhoea
• abdominal (tummy) pain
• muscle and joint pain
• a general sense of feeling unwell

These symptoms, known as acute schistosomiasis, often get better by themselves within a few weeks. But it is still important to get treated because the parasite can remain in your body and lead to long-term problems.

Causes

The worms that cause schistosomiasis live in fresh water, such as:

• ponds
• lakes
• rivers
• reservoirs
• canals

Showers that take unfiltered water directly from lakes or rivers may also spread the infection, but the worms are not found in the sea, chlorinated swimming pools or properly treated water supplies.

You can become infected if you come into contact with contaminated water – for example, when paddling, swimming or washing – and the tiny worms burrow into your skin. Once in your body, the worms move through your blood to areas such as the liver and bowel.

After a few weeks, the worms start to lay eggs. Some eggs remain inside the body and are attacked by the immune system, while some are passed out in the person’s pee or poo. Without treatment, the worms can keep laying eggs for several years.

If the eggs pass out of the body into water, they release tiny larvae that need to grow inside freshwater snails for a few weeks before they are able to infect another person. This means it is not possible to catch the infection from someone else who has it.

Currently, the drug used in most people is praziquantel (Biltricide); however, it only is effective against adult worms and does not affect eggs or immature worms. Treatment with this drug is simple and its dose is based on the patient’s weight with two doses given on one day. However, the drug causes rapid disintegration of the worm which, in turn, allows the human immune system to attack the parasite. This immune response can cause localized reactions, which may increase the patient’s symptoms. Corticosteroids are often used to reduce the symptoms of this reaction. Unfortunately, this response limits the use of praziquantel. Praziquantel and oxaminquine or artemether are used by some clinicians early in infections, or to treat individuals infected with both malaria and schistosomes, respectively.

Surgical care may include removal of tumor masses, ligation of esophageal varices, shunt surgeries, and granuloma removal.

Early antiparasitic treatment, especially with acute schistosomiasis, may allow people to recover completely without developing chronic disease. A few people get the disease but recover completely. Even patients with early chronic disease can improve with drug treatment. However, the prognosis is worse for people who have other health problems (for example, with a suppressed immune system, HIV, or chronic infections such as malaria) and subsequently get infected with Schistosoma. People with chronic disease may improve with careful antiparasitic drug treatments and symptomatic treatment of the complications associated with schistosomiasis.