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Animal Hazards - Bilharzia

Dr Jules Eden, dive medicine specialist and founder of e-med, answers divers' questions - as published in Sport Diver magazine:
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Q - The shores of Lake Malawi have been my home for the last few months. I've been seeking inspiration for my latest work and I thought I'd found the perfect location to galvanise my literary brain into sensuous and romantic outpourings. Sadly after an ill-advised snorkelling trip in the lake I've contracted a vulgar disease called bilharzia instead. I felt fine initially but a few weeks after my dive I was prostrated by severe abdominal pains, fever and diarrhoea. What's the prognosis, doctor?

A - Iím quietly confident that the outlook is good, Kenneth. Youíve been the victim of a nasty water-borne illness which is a growing menace to the idyllic shores of Lake Malawi. Bilharzia (or schistosomiasis Ė careful how you say that) is a disease caused by parasitic flukes that use humans as hosts. The eggs breed in snails that live in the reeds in the stiller areas of the lake, and once theyíre released into the water they develop into larvae that are capable of infecting mammals. They cleverly secrete enzymes that break down human skin, allowing them to penetrate it and migrate to the lungs and liver. Once there, they grow and start feeding on red blood cells, and they may end up moving to the kidneys, bladder or intestine. After loitering maliciously for 6 to 8 weeks the mature worms start producing eggs, anywhere between 300 and 3000 a day, many of which are shed in faeces and urine. Itís the eggs that donít make it out but stay trapped in the body that stimulate a massive immune response, giving rise to the fatigue, fevers, pains, swollen livers/spleens and genital sores that are the hallmarks of the disease. Disconcertingly, the worms survive in the body for an average of 4 and a half years, sometimes much longer. Counting eggs per gram of poo isnít my idea of a good day out, but this is how the disease is most commonly diagnosed. But happily, itís easily treated, by a single oral dose of the drug praziquantel. The WHO is promoting efforts to eradicate bilharzia and some countries have managed it, but Malawi isnít yet one of them. As we all know, prevention is better than cure, so avoid areas known to be infested; don't swim, wash, paddle, push vehicles or wade through rivers or water, especially if slow-flowing or stagnant; don't drink potentially infected water without at least boiling it for a minute or more; and wear protective footwear if you are walking through mud or damp areas near rivers or lakes.

Q - My son and I swam in Lake Malawi this summer. My son, who is 16, did an intensive 5 day scuba diving course.

After reading the travel books, we decided to take action, even though we have no bilharzia symptoms. Sixweeks after exposure, our GP agreed reluctantly to sendoff stool samples for testing for 'all egg infestations'. The results have come back 'normal'.

Should we take any other action?

A - Sadly, Lake Malawi is now known for harbouring bilharzia, and I see your point about getting checked for it now you are back.

Many people who are infected by this nasty parasite do not get any symptoms for a couple of months, but later they may get blood in the urine, a raised fever or blood on the stool. The best test is in fact a blood test for antibodies to the parasite. If this comes back positive then a single dose of a powerful drug called praziquantel is all that is needed.

I don't know what your doc expects to find with a simple stool parasites and eggs test. This is normally something you do to look for bowel bugs rather than bilharzia.

So I think you need to get your doctor to do the blood test, but if you are still asymptomatic after all this time then the chances are that you probably do not have the disease.

If you ever go back to the lake, avoid contact with the snail that is the parasite-human vector by wearing dive boots in the reeds near the shore, and best to swim or dive off a boat in the open water.

Q - I'm planning a trip to Malawi, and obviously want to dive Lake Malawi when I'm there. I've read that there is a problem with something called bilharzia there. Should I take any precautions whilst diving there?

A - You're right there. Lake Malawi always had the reputation of being bilharzia free, but recently more and more cases of this problem have been reported from the Lake. The area most affected is in the Southern part , around a place called Cape Maclear. This may be as it's the most popular part as it's the most beautiful and hence has most visitors.

Bilharzia or schistosomiasis as it's also known, is caused by a nasty little worm that has part of its life-cycle in a freshwater snail, and the rest in the human bladder, liver or blood supply to both. It is contracted when you come into contact with the worm after its come out of the snail. It then burrows through the skin and into the body... the rest you don't really want to hear!

But don't worry, if you take precautions, you'll be fine.

Stay out of the mushy, reedy lakeside areas where the snail lives. Try to dive from a RIB and if you are wading to shore, wear your dive boots.

If you do feel unwell at all, its easily diagnosed with a blood test and then easily treated too.

(other dive medical questions)



   


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