Alvanian Spine Mite

Alvanian Spine Mites are tiny parasitic lifeforms which burrow themselves into the spinal column of vertebrate species, causing back pain for life.

History
When Odo, a Changeling, having lost his shapeshifting abilities, felt a back pain, he believed it was being caused by Alvanian Spine Mites, but Dr. Bashir assured him it was just a pinched nerve.