Schistosomiasis or bilharzia
Schistosomiasis, or bilharzia, is a disease that is caused by parasitic worms. Infestation occurs when parasites that are released by certain types of freshwater snails come in contact with the skin or are ingested.
It is estimated that at least 90% of those requiring treatment for schistosomiasis live in Africa. Schistosomiasis is the second most socioeconomically devastating parasitic disease after malaria.
The symptoms of schistosomiasis include a rash or itchy skin that is followed by fever, cough and chills. In urinary schistosomiasis, there is progressive damage to the bladder, ureters and kidneys. The urinary form of schistosomiasis is also associated with an increased risk for bladder cancer in adults. In intestinal schistosomiasis, there is progressive enlargement of the liver and spleen and intestinal damage.
It’s common for schistosoma parasites to break through the skin of persons bathing, swimming or fishing in contaminated fresh water. Women doing domestic chores in infested water, such as washing clothes are also at risk. Poor hygiene and play habits make children especially vulnerable to the infection.
It’s also important to drink safe water. Drinking water can come from rivers, lakes and reservoirs and should be boiled for at least 1 minute to kill any parasites.
How you get schistosomiasis
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 aren’t 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’re able to infect another person. This means it’s not possible to catch the infection from someone else who has it
Symptoms of schistosomiasis
Many people with schistosomiasis don’t have any symptoms, or don’t experience any for several months or even years.
You probably won’t notice that you’ve 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
- muscle and joint pain
- abdominal (tummy) pain
- a general sense of feeling unwell
These symptoms, known as acute schistosomiasis, often get better by themselves within a few weeks. But it’s still important to get treated because the parasite can remain in your body and lead to long-term problems.
Long-term problems caused by schistosomiasis
Some people with schistosomiasis, regardless of whether they had any initial symptoms or not, eventually develop more serious problems in parts of the body the eggs have travelled to.
This is known as chronic schistosomiasis.
Chronic schistosomiasis can include a range of symptoms and problems, depending on the exact area that’s infected. For example, an infection in the:
- digestive system can cause anaemia, abdominal pain and swelling, diarrhoea and blood in your poo
- urinary system can cause irritation of the bladder (cystitis), pain when peeing, a frequent need to pee, and blood in your pee
- heart and lungs can cause a persistent cough, wheezing, shortness of breath and coughing up blood
- nervous system or brain can cause seizures (fits), headaches, weakness and numbness in your legs, and dizziness
Without treatment, affected organs can become permanently damaged.
Treatments for schistosomiasis
Schistosomiasis can usually be treated successfully with a short course of a medication called praziquantel, that kills the worms.
Praziquantel is most effective once the worms have grown a bit, so treatment may be delayed until a few weeks after you were infected, or repeated again a few weeks after your first dose.
Steroid medication can also be used to help relieve the symptoms of acute schistosomiasis, or symptoms caused by damage to the brain or nervous system.
Preventing schistosomiasis
There’s no vaccine for schistosomiasis, so it’s important to be aware of the risks and take precautions to avoid exposure to contaminated water.
If you’re visiting one of these areas:
- avoid paddling, swimming and washing in fresh water – only swim in the sea or chlorinated swimming pools
- boil or filter water before drinking – as the parasites could burrow into your lips or mouth if you drink contaminated water
- avoid medicines sold that are advertised to treat or prevent schistosomiasis – these are often either fake, substandard, ineffective or not given at the correct dosage
