Pop-eye and Dropsy Tropical Fish
There are no such diseases as pop-eye and dropsy. To any hobbyist who has a favorite fish die with its eye popping out of its head, or with its abdomen swollen like a balloon, this may seem like a strange statement. The point is to emphasize that these conditions are only symptoms of an underlying disease. Treating the symptoms without doing anything about the disease is a waste of time and effort.
Pop-eye (exophthalmos) can be caused by a variety of conditions including abscesses (tuberculous and nontuberculous), generalized edema and tumors. In commercial aquariums where highly aerated water under pressure may be added directly to the tanks, bubbles may form on the fish’s body causing a condition known as air embolism but this should not affect home aquariums. In humans, exophthalmos is most often caused by a dysfunction of the thyroid gland but can also be caused by a tumor or infection.
Dropsy (generalized edema) in humans can be due to chronic heart failure, severe kidney disease, or chronic liver disease. In fish similar causes are found but heart disease has not been recognized in aquarium fish. Tuberculous and nontuberculous infections in the fish’s kidney and liver are the most common causes of the condition. One platy seen by the author had a marked fibrosis and thickening of its body muscle which mimicked dropsy in external appearance.
The treatment of both of these symptoms depends on the underlying disease which usually. cannot be diagnosed without destroying the fish and studymg the organs. Without this diagnosis a rational approach is to isolate the affected fish and treat it with antibiotics. Unfortunately, m order for pop-eye or dropsy to occur, any causative infection must be present in an advanced stage, and cures are rare. The infections usually causing pop-eye and dropsy have an indolant course-rapid infections will usually kill without causmg such symptoms. Occasionally dropsy may recede spontaneously but it will recur and ultimately kill the fish. Pop-eye usually does not recede.
The hobbyist should realize that bactenal infections in fish will sometimes heal spontaneously. Old fish have been found showing healed abscesses in their body although they had never been treated for any illness nor ever thought to have been sick.
