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I am convinced that most koi hobbyist has seen dropsy symptoms in fish. I am further convinced that a large percentage of hobbyists that have noticed these symptoms initially thought the fish is overweight, laden with eggs etc. I am also sure that the initial humorous reference to “our pregnant fish” turned to alarm with the rapid expansion of the abdomen and severely bloated appearance. Most owners realize that something is seriously wrong when pop-eye develop. A few days later when the internal pressure causes the scales to protrude from the body, the alarm turns to dread. Dropsy is arguably the most feared and common "disease" of the pond.  The reason is that unless dropsy is caught in the very early stages, a cure is almost impossible. The above statements are based on the numerous calls that I have received over the years, only to arrive at a pond and having the difficult task of convincing the owners that treatment will serve no purpose. I have also attempted to treat such fish when the owners insisted. Unfortunately the treatments were without any success because in advanced stages, after the body has swelled, the eyes have bulged and/or scales are sticking out (like a pinecone) this disease is usually always fatal.

Dropsy is not a disease, it is a sign of a disease. The word “dropsy”, as generally used by hobbyists is a reference to the accumulation of fluids in the visceral cavity of a fish. This fluid buildup causes the abdomen to swell. In severe cases the distention is so great that the scales stand out from the body. When viewed from above, the fish takes on a pine cone-like appearance. Hence the Japanese name for the problem — "matsukasa disease" or "pinecone disease”. Several reasons exist for the pine-cone appearance in fish and to diagnose every occurrence accurately, the fish must be sacrificed and the organs submitted for various laboratory tests. It is far easier to describe the symptoms of dropsy than to identify the specific cause of it. There is no apparent single cause of dropsy and it usually only affects individual fish.

Several bacterial diseases — including aeromonad disease (Aeromonas hydrophila), pseudomonad septicemia (Pseudomonas fluorescens) and vibriosis (Vibrio anguillarum) — can result in dropsy. All these bacteria are common in fish ponds and may be present amongst the healthiest populations of koi. The question really is why and how do these bacteria suddenly go out of control and produce this deadly malady? The answer is fish stress. The appearance of this disease is especially likely in low water temperatures, but it can occur at any time during the year.

Most scientists agree however that some stressor, whether it is overcrowding, bad water quality, parasites, extensive handling, poor nutrition, unstable temperatures etc. may trigger the invasion by viral or bacterial pathogens into the blood. These pathogens find their way into internal organs, destroying it. Unfortunately, by the time an infected fish has blown up like a football, there is little that can be done to save it. Extensive damage has already occurred to internal organs, and infection is rampant throughout. If caught in the early stages, these diseases can be treated successfully with a combination of improved water quality management and the use of antibiotics. If a fish seem to be diseased, it should be isolated in a hospital tank. Although it is agreed that dropsy is generally not contagious, a sick fish in the pond does stress other fish and it also serves as a virulent breeding ground for the bacterial pathogens, making it harder for the other fish to fight off the disease.

Dropsy-like symptoms may be caused by a number of other problems, including tumors, tapeworms, impacted egg masses and blocked intestinal passages. Each of these can be remedied by the proper treatment like surgery, de-worming and so on.

As stated above, the difficult parts are early detection of the problem and early accurate diagnosis. Frequently, secondary internal bacterial infections follow these problems if they are not dealt with quickly. Frankly, it is nearly impossible for the hobbyist to determine with any precision the underlying cause of a dropsical condition. This is why the use of drugs to "cure" the problem meets with limited and unpredictable success. As often as not, the fish will live or die irrespective of drug treatment. Most often a dropsical fish dies. Perhaps it will not die immediately, but it will die within several days, weeks or months. Indeed, in instances where dropsy is caused by internal infections, the bloating may disappear for a time, only to return a bit later with a vengeance. Thus, many reports of dropsy "cures" are just misinterpretations of the temporary regression of the disease.What is really peculiar about dropsy is that sometimes an affected fish may eat right up to a few minutes before it expired. Because dropsy results in a significant change in the fish's volume and density, it is often accompanied by buoyancy and swimming problems. Either the animal sinks to the bottom or it floats at the surface.

While the dropsy symptoms are not contagious and will generally not infect other fish in the pond, the conditions that caused the symptoms are contagious and needs to be investigated. The most common cause is a breach of the outer defences of the fish such as the cuticle by parasites or injury, followed by internal bacterial infection. Untreated ulcers or injuries may cause the infection to become systemic and attack the internal organs.

Recently I again had the unfortunate task of visiting a client’s pond where the unmistakable symptoms were prevalent in a very nice Shiro Utsuri. First one must determine if it is impacted roe or a tumour that is causing the symptoms. Impacted eggs or roe will feel like very soft “putty” when gently squeezed, while a tumour may cause a solid lump that can be detected amongst the swelling. In this case the fish was a consistent watery bloating that felt firm to the touch.




As can be seen from the photos, it was not full-blown dropsy yet, although the eyes were beginning to bulge.


There are several experts on koi disease that will argue that a koi don’t have full blown dropsy unless the scales and eyes are protruding, therefore the koi was put into a heated quarantine pond. The water was treated with salt to 0.5% and antibiotics were injected on three consecutive days, to no avail. I must admit that salt did purge the intestines but the osmotic imbalance could not be rectified. The fluid in the body cavity remained until the fish perished. This specific fish did not display the normal protruding scales and eyes, but the redness on the belly was a testimony to systemic infection.



Notice the how the distention of the belly actually "dwarfes" the tail segment! The fish did not lie on the bottom or floated to the surface in the quarantine tank. Remarkably it stayed in mid-water. The redness on the belly was therefore not caused by the fish remaining on the bottom of the pond. (So called pressure sores). The question will remain: What caused the symptoms? Was it a viral or a bacterial infection or was it both. Was it a tumour that has grown so big that it actually inhibited some organs from functioning properly? One will unfortunately never know!



Unfortunately, despite my best efforts, the fish did not survive. Frustrating!

Now also see bacterial infections

Last Updated on Thursday, 05 August 2010 21:19