I think its mostly a film set
I think the bugs etc are real but I don't believe that they really sleep in a camp in an actual jungle and wash in rivers etc. i mean surely the health and safety implications of if it was real would make it not worth the risk?
or my other theory is I think they sleep in a hotel and are only in the "jungle" for the bits they film
and i reckon the slebs sign a contract saying they won't ever reveal the truth or they will be sued for £100000000000s by itv.