The gangrenous tissues of a zombie are largely inhospitable to brain-flukes, but in a pregnant female zombie, the worms adapt to the developing embryo and take on a flesh-boring form, shaping the new creature into an effective carrier. Constantly gibbering and gurgling, the zombie spawn itself is virtually mindless, but the tunneling parasites use strategic jolts of pain to puppeteer their carrier as effectively as a complete brain, seeking out new hosts to drill their way into.