A boy who is fond of swimming in a pond finds himself passing urine with traces of blood. He is like to have contracted?

Step 1: Analyze the question A boy swims in a pond and later passes urine containing blood (haematuria). We need the disease linked to contact with fresh water and blood in urine.

Step 2: Explain the concept

• Schistosomiasis (bilharzia) is caused by blood flukes of the genus Schistosoma. The species S. haematobium causes urinary schistosomiasis. The larvae (cercariae) are released by freshwater snails (the intermediate host) and penetrate the skin of people who swim or wade in infected water. The adult worms live in the blood vessels around the bladder, and their eggs damage the bladder wall, causing blood in the urine.
• Onchocerciasis (river blindness) is caused by a filarial worm, Onchocerca volvulus, and spread by the blackfly (Simulium). It causes skin nodules, itching and blindness, not bloody urine.
• Poliomyelitis is a viral disease spread through contaminated food or water (faecal-oral route). It affects the nerves and causes paralysis.
• Salmonellosis is a bacterial infection (typhoid and food poisoning types) spread through contaminated food and water. It causes fever and gastrointestinal symptoms, not bloody urine.

Step 3: Apply to the question Swimming in a pond means contact with freshwater, which is where the snail host lives. Blood in urine is the classic sign of Schistosoma haematobium. Only schistosomiasis fits both clues.

Step 4: Answer The correct option is A. schistosomiasis.

Exam tip: Link the clues. "Swimming or wading in freshwater + blood in urine" means Schistosomiasis. Remember "snail = schisto", and "blackfly = onchocerciasis".