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Bilharzia – Dr Dick Stockley

So what is the best advice?

People ignore medical advice anyway: they drink too much, eat too much, smoke, and work on weekends. And they’re going to go in the lakes and rivers. Water sports are healthy exercise: it’s difficult to smoke a cigarette when you’re waterskiing.

The best advice is advice that people might follow: so I say go sailing, fishing and waterskiing. Go out on a boat trip, go for a dip if you’re hiking past a lake, watch out for crocodiles if you’re going skinny dipping at midnight; and take bilharzia seriously. We have mostly S. Mansoni in Uganda and everything I’m saying applies to Mansoni.

Schistomes LifeCycle CDC diagram
Schistomes LifeCycle CDC diagram

The cercaria lives up to a day but are most active in the first few hours. Most infection is from actual immersion in water with the infected snails: however they can be pumped into a tank, go down a pipe and come out a tap. You can get bilharzia from a shower. Municipal water supplies are safe. Swimmers itch This is the itchy spotty rash you get from cercaria penetrating the skin. Most swimmers itch is from other species of Bilharzia, most likely birds, avian schistosomiasis. You itch for a few hours or days but they cannot infect you. However the human schistosomes can also cause swimmers itch: there’s no way of knowing, just get tested after 6 weeks.

Acute Bilharzia

Katyama syndrome or conversion fever. After wriggling through the skin the cercaria lose their tail and become schistosomules. Somehow they get to the liver, and the boys and girls meet. No one knows how. One theory is they whistle and burp. Or they meet in intrahepatic discotheques. That’s why the Nile river rafting guides hold parties that play very loud music after rafting, in an attempt to confuse the schistosomes and prevent them meeting. They spend 3 to 6 weeks in the liver, they grow to about 2 cms long. The male has muscles (don’t we all?) the female is just a long egg laying tube (no comment). He wraps himself round his lady and they spend the next 15 years in permanent copulation. No wonder we feel tired.

He swims down the hepatic veins to the terminal venules of the bowel, they get jammed in the narrow vessel and she starts laying eggs. They are hidden from our immune system by the tegument, think Harry Potter and his invisibility cloak, but the eggs cause a big immune response, local and systemic and this causes the acute fever of katayama syndrome.

You may have diarrhoea, a rash, cough, nausea and rather unwell. Or nothing at all. It’s rarely diagnosed. In the tropics any fever is called malaria. The clue is high eosinophil count and a negative malaria rapid. It goes away on its own.

Schistosoma worm Bilharzia
Schistosoma Fluke (Bilharzia)

Chronic Bilharzia

The loving schistosome couple live for at least 15 years causing no problem other than laying eggs. The eggs are supposed to get through the tissue into the bowel lumen, get washed into the lake, hatch and go and torment a snail for 2 years. Instead most get stuck. They provoke an immune response that causes a granuloma. This may not cause much damage in the large bowel, but ectopic couples migrate into the surrounding tissue such as ovaries, tubes, or prostate if you have one. They can get completely lost and finish up in the spinal canal or into the brain. This was considered rare or even denied 20 years ago but is now a recognised cause of epilepsy, paralysis and death.

Over the years chronic inflammation turns into permanent fibrosis. Fibrosis of the bowel causing chronic inflammatory bowel disease, fibrosis of the tubes or ovaries causing infertility and pain, fibrosis of the prostrate causing obstruction, or pipe stem fibrosis in the liver We have seen it all. We used to find that the commonest cause of chronic gynaecological problems in expats was Bilharzia. We have seen boys in their late teens with prostate problems, needing dilation and surgery before they are 30. We have seen patients with spinal cord lesions causing very sudden onset of progressive paralysis. One email was a lady who had seen 4 gynaecologists in USA with chronic pain, finally had a laparotomy where they found her ascending colon stuck to the posterior abdominal wall. Sounds like Bilharzia we said: finally diagnosed 5 years after leaving.

The good news is most of this is rare! Most people just feel vaguely unwell, never quite right bad guts and tired all the time. The bad news is how many are never diagnosed? How many expats with Bilharzia go home, continue to see their chosen specialist, get diagnosed with IBS, endometriosis, chronic PID, recurrent UTI or depression, and only get better when the schistosomes die of old age after 15 years?


The symptoms are vague, and are usually diagnosed as something else because few doctors think Bilharzia. So first of all think Bilharzia! Take it seriously. It probably isn’t but it might be. Our advice is after any exposure, get tested. Any vague symptoms get tested. When you leave the country get tested. Any long-lasting vague unwell after being in Africa think “what if it’s bilharzia.” Any sudden neurological symptoms such as headaches, dizziness, tingling or numbness get tested. Vague rather annoying tingling in the fingers on Monday can be paralysed from the neck down in ICU on a ventilator on Thursday.

Please be wary of advice from those who are not up to date. We have mostly Mansoni at our end of the lake that doesn’t present with haematuria or eggs in the urine. You might find eggs in the stool: if there are enough to find and use special concentration techniques. In most patients if you find an egg it’s a bit of a fluke.* Blood tests for antibody are low sensitivity and specificity: many cases do not have detectable antibodies. Even PCR can miss it. So what to do?

The cathodic antigen point-of-care tests are excellent screening tests. It’s a quick simple very cheap urine dip stick. Schistosomes burp: the antigen is burped out into the blood and can be detected in the urine. The test can be strong positive, weak or negative depending how many flukes you are hosting. Early research suggested too many false positives, but modern research shows that those weak tests are correct but the other tests failed to detect it. For more detail see the longer article on the website.

You’ve read how serious Bilharzia can be. If you have a positive urine antigen test is it really worth it to say no I don’t want treatment, the antibody test is negative? My strong advice is to take the medicine anyway. It might save your fertility or avoid prostrate surgery when you’re 30.


Treatment is complicated so read more details on the website. Praziquantel paralyses the adults, the tegument drops off, they float back up to the liver and they are attacked by the immune system. First dose most may survive but immunity is primed. Second dose more will die. Most people will need a third dose.

Our advice has evolved over the years. Best for most people is first time take a dose of 60mg per kg at night with food for 3 nights. Successful treatment results in a significant immune response to the dying schistosomes: read the website. Then test again after 3 weeks. If still positive take another dose one night only. Test again. We expect each test to get more faint. Once negative, take another dose after a month just to be sure. Yes the medicine is horrible, the immune reaction is unpredictable and paediatric preparations are still on the horizon.



Bilharzia is an unpredictable disease, ranging from unrecognised to fatal neurological involvement. Diagnosis is often missed, but proper treatment is successful. Read the full website.
Bottom line: take Bilharzia seriously.
* It’s a pun. Schistosomes are flukes. 🙂

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