Ok Some Background Info Before My Question. I'm Making A

Ok some background info before my question. I'm making a character that has a symbiote connected to him. Think Venom from marvel comics. But my symbiote drains off and replaces the cerebra spinal fluid of the host with itself to gain access to the nervous system of the Host to better aid and or control it.

Now should the symbiote be removed from the Host.

What damage is immediately dealt in such a situation and is swift death a possibility?