Parasited - Little Puck _top_

: Sickly kittens are often "infested" with fleas. Useful treatments include:

By "parasiting" Little Puck, the Grief Eater allows him to live out a fantasy. Every "upgrade" the parasite gives (claws, camouflage, wall-crawling) is actually Puck’s body shutting down further. The final level—where Puck merges permanently with the shadow—is actually the moment of brain death. Parasited - Little Puck

Reports of Parasited included:

By the time it reached the stray dog—a gentle, flea-bitten collie named June—Little Puck had grown to the size of a walnut. It nestled behind her left eye, not in the brain but against the optic nerve, where it could taste everything June saw. Sun on pavement. The blur of a thrown stick. The face of the boy who left out bowls of food. : Sickly kittens are often "infested" with fleas

: Parasites often cause diarrhea and dehydration. The final level—where Puck merges permanently with the