Fish acts as intermediate host in –
**Core Concept**
The question is testing the student's knowledge of the life cycle of parasites, specifically the role of intermediate hosts in the completion of the parasite's lifecycle. Fish serve as intermediate hosts for certain parasites, allowing them to undergo a crucial developmental stage before infecting their definitive hosts.
**Why the Correct Answer is Right**
In the case of the schistosome parasite, fish act as intermediate hosts. When an infected snail releases cercariae, they penetrate the skin of a fish. The cercariae transform into schistosomula within the fish, where they mature into infective stages. Humans become infected when they consume contaminated water or food containing these infective stages. This process highlights the importance of understanding the lifecycle of parasites in diagnosing and preventing infections.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because birds act as intermediate hosts for the avian schistosome, *Schistosoma haematobium* is not typically associated with intermediate hosts in fish.
**Option B:** Incorrect because this option is not a correct answer choice, but if you were to choose an incorrect option, it would not be a suitable intermediate host for this question.
**Option C:** Incorrect because this option is also not a correct answer choice, and fish are not typically associated with this type of parasite.
**Clinical Pearl / High-Yield Fact**
Fish act as intermediate hosts for certain parasites, including schistosomes. This knowledge is essential for understanding the transmission dynamics of these parasites and for developing effective prevention and control strategies.
**Correct Answer: A.**