In the life history of schistosoma (Bilharzia), one of the following is intermediate host
man
snail
mosquito larva
crayfish
fish
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bilharzia(snail fever) is a parasitic disease caused by different species of tremadoes, a parasitc worm of d genus schistosoma.d snail serves as d intermediary agent btw d mammalian host.its normally in places where dere s poor sanitation and dirty water. Fresh water snail dat r infected by d parasitc eggs infect d water and it gets 2 humans
water snail is the secondary or intermediate host while any animal dat drink d contaminated water is a primary host e.g sheep...go to relevant of bio to agric u will see details of it
...after the infected person (i.e the Definitive Host) has passed urine containing the egg, in a fresh water, it hatches in the water to and then releases a cilliated miracidia, which then penetrates a specific snail host, Bulinus globosus, (i.e Intermediat Host...) where it undergoes series of metamorphosis, thus ready to re-infect a new definitive host...
We’re talking about schistosoma, which is the parasite that causes bilharzia, also called schistosomiasis. That’s a disease you can get if you come into contact with water where this parasite lives. I know it sounds scary, but it’s actually a very predictable life story once you slow down and go step by step.
So the question is asking about the intermediate host. That word intermediate host means the creature in which the parasite lives temporarily before it gets to its final home. The parasite has a life cycle, and it needs two different hosts to grow up properly. One is the definitive host, where it reaches adulthood and can reproduce. The other is the intermediate host, where it grows but doesn’t fully mature.
Let’s look at the options and understand them.
Option A: man. Man is actually the definitive host, not the intermediate host. That means the parasite becomes an adult in humans and lays eggs inside us. So this is not the intermediate host.
Option B: snail. Snails are the intermediate host. This is where the parasite goes after leaving the water as eggs, hatches into a larval form, and multiplies. The snail is like a little temporary home that helps the parasite grow before it jumps back into the water to infect a human.
Option C: mosquito larva. Mosquitoes are involved in other diseases like malaria, but they have nothing to do with schistosoma. So this is wrong.
Option D: crayfish. Crayfish are sometimes hosts for other parasites, like the ones that cause lung fluke infections, but not bilharzia. So also wrong.
Option E: fish. Fish are not part of schistosoma’s life cycle. This is wrong too.
So the correct answer is B, snail. The snail is essential because without it, the parasite cannot develop into the stage that infects humans.
Here’s a way to picture it: imagine the parasite as a little traveler. It hatches from eggs in water and swims around until it finds a snail. It lives there, grows, and then bursts out into the water again as a stage that can infect humans. When it touches human skin, it burrows in, goes through the bloodstream, and grows into an adult in the blood vessels. That’s the full cycle. Humans are the final home, snails are the pit stop.
