The axolotl I know was infected by a frog that shared its tank, although separated by a divided. Aparently the disease is or can be water borne (speculating here) because the infected animal must have all of its own equipment (feeding tweezers, siphon, etc.) to prevent spreading the disease.
I don't mean to suggest that your animal has this virus. I just mean that it should be taken to a vet for testing because you never know what could be the culprit.
-Eva