Furunculosis Disease

Furunculosis on tropical fish

Furunculosis is a disease of fishes which gets its name from the fact that the lesions symptomatic of this illness are very similar to human boils and furuncles. The disease often hits jobbers and dealers of fishes who maintain a great number of a single species in one large aquarium. Most often young imported specimens get this infection from filthy aquarium conditions and from poor handling.

Symptoms
The disease manifests itself with ulcer-like sores on the body of the fish. It usually starts on the caudal peduncle, but it can break out anywhere. Most commonly the sores might appear on the bases of the fins and this leads many to suspect that the disease is a finrot. Fortunately the treatment of the two diseases is the same.

In general this disease might be classified as a blood poisoning (septicemia) as the blood transports the bacteria to all parts of the fish's body where they gather in some small blood vessel (usually the capillaries), mass together, reproduce and destroy all the tissues about them. The disease in this stage looks like very small red marks under the skin of the fish and most people think the fish has bruised itself. Soon afterwards, a boil forms which is filled with pus, blood and broken down bits of tissue. When these boils break, they form ulcers and the pus from the boil is liberated into the water where the bacteria can attack the other fishes. Very small fishes usually die before the boils can break since the disease is so rampant inside the fish that it dies of internal disorders.

The bacterium which causes the disease is known as Bacterium salmonicida and was first described by two German trout workers, Emmerich and Weibel in 1894. The organism measures about 3 microns in length and has rounded ends. Bacteriologically it is Gram negative, nonmotile and nonsporulating. When grown in an agar medium it discolors the medium a light tan.

Treatment
A simple treatment is the addition of a sulfa drug (sulfamerazine) to the food of the fish. About 500 mg. per ounce of food is sufficiently strong to combat the disease. Fishes should be kept on the medicated food for at least 30 days.

The use of Aureomycin and Terramycin factor in most fish foods has made the disease easily controllable; raw Terramycin, 500 mg. per 15 gallon aquarium, one day per week, controls the infectious aspect of the disease. All aquaria which contained diseased fishes should be thoroughly sterilized prior to reuse. Potassium permanganate is about the best disinfectant to use.