Intermediate host for schistosoma haematobium is: March 2013
**Core Concept**
Schistosoma haematobium, the causative agent of urinary schistosomiasis, exhibits a complex life cycle involving a definitive host (human) and an intermediate host, where the parasite undergoes significant morphological and physiological changes. This intermediate host is a crucial component of the parasite's life cycle, facilitating the transmission of the disease to humans.
**Why the Correct Answer is Right**
The correct intermediate host for Schistosoma haematobium is the freshwater snail, specifically species belonging to the genus Bulinus. The parasite undergoes a series of developmental stages within the snail, including a larval stage called a cercaria, which is released into the water. The cercariae then infect humans, leading to the establishment of the definitive infection. This snail-host interaction is essential for the transmission of schistosomiasis.
**Option A:** The cat is not an intermediate host for Schistosoma haematobium. Cats are not typically involved in the parasite's life cycle and are not commonly infected with this species.
**Option B:** Dogs are also not intermediate hosts for Schistosoma haematobium. While dogs can be infected with other species of Schistosoma, they are not involved in the life cycle of S. haematobium.
**Option C:** Rats are not intermediate hosts for Schistosoma haematobium. While rats can be infected with other parasites, they are not relevant to the life cycle of this particular species.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the use of freshwater for irrigation, swimming, or drinking can increase the risk of schistosomiasis infection. In endemic areas, using protective measures such as wearing shoes, clothing, and applying insecticides can help prevent the transmission of the disease.
**✓ Correct Answer: D. Fresh water snail. Freshwater snail is the intermediate host for Schistosoma haematobium.**