If you cut into the livers and you will be able to tell if its fluke as the little sods will be visible , sounds like the cystic stages (cystercurcus tenuicolis) of the dog tapeworm Taenia Hydatigenia which the sheep, cattle and DEER are the host in the worms life cycle .
As a Meat Inspector I see this every day , this does not affect the meat in any way , just rejection of the liver , just to say also check in the diaphragm
as you might see a little sac filled with a liquid hanging from the flesh , this is where the the worms have passed from the liver and stuck to the diaphragm wall