Q: I swam in Lake Malawi this summer, and my son did an intensive five-day scuba diving course. Although we have no bilharzia symptoms, we thought it best to make sure. Six weeks after exposure, our GP agreed to send off stool samples for testing for 'all egg infestations'. The results have come back 'normal'. Should we take any other action?
Gaye Sheridan

Dr Jules Eden replies: Sadly, Lake Malawi is now known for harbouring bilharzia, and I understand your concern 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 fever or blood on the stool. The best test is 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. Ask your doctor for 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 swim or dive off a boat in open water.

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If you have any questions you want to ask Dr Jules Eden, email travel.doctor@theguardian.com, or write to The Flying Doctor, The Guardian, 119 Farringdon Road, London EC1R 3ER.

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