Control by Ed Kurtz
Leon Weissmann is an introverted loner with no control over his life. His only joy is the menagerie of insects, spiders, and scorpions he tends to in his garage. When he acquires an illegally poached rainforest spider, he unknowingly contracts a rare strain of fungus that enables him to control people, to make them do anything he wants. As his power grows, Leon begins to abuse it until there are bodies in his wake and a coterie of brainwashed disciples under his influence. But soon Leon suspects that the thing growing inside his head may be the one with the power… It wants to come out. To reproduce. It wants to control everyone.
I think the cover is some what creepy.
