Sarcoptic Mange

AKA scabies, particularly in humans.

A cutaneous disease of mammals* caused by mites of the genus Sarcoptes including Sarcoptes scabiei. The mites burrow under the skin and lay eggs, causing itching, hair loss, and skin damage from both the mite and the host's scratching.

Best known for afflicting dogs, but many types of mammal can be infected. While Sarcoptes scabiei is responsible for all forms of sarcoptic mange, there are many varieties specific to certain species. For example, while Sarcoptes scabiei var. canis can infect humans, it can't reproduce and will die out in a few weeks if not replenished from a doggy source.

The female Sarcoptes scabiei digs a honeycomb of burrows in the upper layer of the skin, laying eggs along the way. The adult mites feed on the host's serum, which will ooze into the tunnels and may form a dry crust at the openings of the tunnels. Eventually the mite will die in the tunnel. Soon the eggs hatch, and the larvae molt into nymphs, feeding on serum and skin debris. At the time of the final molt, the now adult mites head to the surface of the skin to mate. The males die shortly after mating, and the females start digging tunnels. Mites usually travel between hosts by direct bodily contact, but they can live for days away from any host, and so may be spread through infected bedding, etc.

Phylum Arthropoda
Class Arachnida
Order Parasitiformes
Suborder Astigmata
Sarcoptes scabiei

Distribution in worldwide, infects many varieties of mammals*. Round body, eight legs, under 0.6 mm long.

* I have found one reference to Grey Cheek Parakeets having sarcoptic mange. Other than that, all cases I can find occur in mammals.