I've been playing a bit of parasite recently and i noticed this bug, searhed the forums and found not threads similer.
Basicly when you are controling a creep you can select parasite by tabbing or clicking on portrait. The bug occurs when you press infest again(as parasite, not the creep). Ut plays the "fake death" animation and sets the cooldown back to 30 seconds. Can be a porblem when your are buying items, then find you have to de-infest the creep to respond to a gank. not sure whether it still heals or not.(I don't think it does)