An Egyptian fisherman develops lower abdominal pain and pain on urination, and reports seeing blood in his urine. Which of the following parasites is the most likely cause of urinary symptoms in this patient?
## **Core Concept**
The patient's symptoms of lower abdominal pain, pain on urination (dysuria), and hematuria (blood in urine) suggest a urinary tract infection or a parasitic infestation affecting the urinary system. Schistosomiasis, a parasitic disease caused by infection with *Schistosoma* species, is a significant health issue in certain parts of the world, including Egypt.
## **Why the Correct Answer is Right**
The correct answer, *Schistosoma haematobium*, is the most likely cause of urinary symptoms in this patient. This parasite is known to cause urinary schistosomiasis, which presents with symptoms similar to those described: abdominal pain, dysuria, and hematuria. *S. haematobium* primarily inhabits the venous plexus of the urinary bladder, leading to inflammation, fibrosis, and the clinical manifestations observed. The parasite's eggs, which are excreted in the urine, cause the pathology.
## **Why Each Wrong Option is Incorrect**
* **Option A:** *Schistosoma mansoni* primarily causes intestinal schistosomiasis, characterized by symptoms related to the intestines, such as diarrhea and abdominal pain, rather than urinary symptoms. It inhabits the mesenteric veins and its eggs are excreted in the feces.
* **Option B:** *Schistosoma japonicum* also causes intestinal schistosomiasis and is less commonly associated with urinary symptoms. It is prevalent in Asia, particularly in China.
* **Option D:** *Schistosoma solium* is not typically associated with schistosomiasis; it is actually a cause of taeniasis (tapeworm infection) and cysticercosis.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that *Schistosoma haematobium* infection is strongly associated with an increased risk of bladder cancer, particularly squamous cell carcinoma. This association makes it a critical condition to diagnose and treat promptly.
## **Correct Answer:** . *Schistosoma haematobium*.