From Lost Fables Wiki
Naturally occurring, mostly in caves
An infested host coming too close will spread the mites, which can jump up to a meter. Once they kill a host, they exit the body in a hideous mass exodus.
Normally domestic animals
At the beginning, they are merely skin-deep, and extremely itchy. If caught at this stage, a bath in vinegar is typically enough to kill the mites. When the mites are allowed to progress for several weeks, however, they reach the end of their life cycle and burrow into the skin, where they lay eggs. A month or so of continuous itchiness later, the miracle of life happens, and the eggs begin to hatch inside the host, at which time the itching suddenly turns to hideous agony while the mites begin to travel around inside their unfortunate victim. They seek out the most electrically active cells in the body, leading them to greedily devour the nervous system first. Over the course of a day, the host will start to lose feeling and fine motor control in their extremities, before strong delirium sets in. Eventually they become fully paralyzed and perish as the mites reach the brain and devour it. Once done, they burrow their way back out of the host and flee them in a mass exodus, and seek new hosts. In this way, brain mites can spread through entire colonies of furred beastfolk, killing all of them if they don’t take proper precautions.
Left untreated, this will kill
Early on, an hours-long vinegar bath is enough to kill the mites. After the first several weeks, when they burrow into the skin, the only cure is to completely shave the subject and perform a days-long procedure on their hole-ridden flesh to remove each and every egg, a process which is usually quite agonizing, and due to the scar tissue it leaves, causes large patches of hairless skin to remain on the subject.