Neon Tetra Disease

Neon Tetra disease is a common parasitic disease named after the species most affected by it. Although it's typically seen in neon tetras, it can infect other types of fish if not properly handled. Neon tetras are mostly affected for a number of reasons, mostly because of inbreeding (due to popularity), improper husbandry during commercial distribution, and improper husbandry in the home aquarium. This parasite will spread in the aquarium on its own, however, as fish tend to pick at and eat carcasses of other fish, this is usually how I've noticed it spreads. Therefore, the best practice is to euthanize affected individuals and always remove bodies of deceased fish. 

Symptoms

Neon tetra disease causes a few different symptoms. The most notable occurs in tetras, as these fish are normally fairly tight shoaling. Infected individuals will separate themselves from the main group as if to try to keep the disease from spreading. Other symptoms include erratic swimming, faded colors, internal cysts that can cause a lumpy appearance to the fish, and other wasting issues. The spine is the first part to go, which is noticeable in neon tetras, as the bright blue line, which is normally slightly curved, will become "S" shaped or even go straight as the spinal muscles will wither away. Secondary infections are also common as the disease progresses, so Finrot is quite common. 

Treatment

Effective treatments are few and far between. By the time symptoms really appear well enough to be identified correctly, treatment is ineffective. The best option is euthanasia or just hoping for the best outcome, as recovery is possible, but I've never seen one recover from separating from the main group. Always remove dead bodies from the aquarium.