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Dermocystidium
Symptoms:
Dermocystidium is a disease that affects the skin of koi and can be found on the gills, fins or body. It causes raised swellings varying in size from 1-2 cm to 10 cm. The lesions are pinkish red and vary in shape from circular to elongated ovals. As the lesion swells, the skin covering the area becomes progressively thinner, at which point it is possible to see white hyphae inside, giving the swelling a whitish, cloudy appearance.
Cause:
Fungal infection. Because of the presence of both spores and hyphae it is currently believed to be a fungal infection, although some authorities class it with the protozoa. It is not known how the spores infect fish, whether they have to find entry into the epidermis, either by way of an open wound, or whether they are able to burrow under the skin. The lesions produced by this illness swell and rupture, spreading thousands of infectious spores into the water. This disease seems to be a spring-time disease, lasting some 6-8 weeks. Recurrence has been reported in previously infected ponds.
Treatment:
There is no known treatment. Direct applications of malachite green and potassium permanganate have proven ineffective against the spores. Although Dermocystidium is not usually fatal, it does threaten fish with the possibility of contracting a secondary infection. Antibiotic treatments and regular cleaning of the wounds will help prevent secondary infections as well as aid in recovery. It is also important, as will all illnesses, to keep water conditions at optimal levels so as to reduce any stress the fish may be experiencing.
