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Ichthyosporidiosis: disease of black spots

Disease Ichthyosporidiosis: It is a disease caused by a fungus (Ichthyosporidium Hoferi) that produces tiny black dots on the skin of the fish, with the appearance of sandpaper.

Disease Ichthyosporidiosis: It is a disease caused by a fungus (Ichthyosporidium Hoferi)


Sandpaper disease. (Due to the appearance that the skin presents when it is covered with the tiny black granites that characterize this pathology and that corresponds to necrotic areas of the dermis.)

Bass with Ichthyosporidium


The small black granites give a very particular roughness to the skin, and as the disease progresses, scaling and open sores may appear, giving rise to hemorrhages. Blackheads are due to tissue necrosis. Abdominal swelling due to fluid accumulation.

This external symptomatology is also evident at the level of certain internal organs such as the liver, kidney or heart. The tissues may be necrotized, but the most common, aside, is the presence of white granules, the result of the connective tissue that encompasses the pathogens and that is the defense mechanism that the cell finds to fight a pathogen that they are unable to destroy. .

Secondarily, it can appear: ascites (accumulation of fluid in the abdomen), imbalances in swimming, loss of appetite, bone deformations and even emaciation, especially in the case of young fish.

One of the main problems in diagnosing this disease is that its symptoms can be confused with other diseases. For example, the granules seen in internal organs are also common to tuberculosis, so histopathological analysis is necessary to make a correct diagnosis.

Ichthyosporidium Hoferi


The disease is caused by the aquatic fungus: Ichthyosporidium Hoferi, which is characterized by a globular shape (standard size: 20-150 microns), inside which more than ten nuclei can be observed.

The entry of the pathogen into the fish is via the oral route, through the hyphae or spores of the fungus that may be in the food that the animal ingests. When they enter the digestive tract, the spores hatch and give rise to an emboid shape that is able to cross the intestinal epithelium and reach the circulatory system, which distributes them throughout the body. Therefore, it is not surprising that the most affected organs or tissues are the most irrigated, such as: liver, kidney, heart and muscles.

Once the amoeboid form has reached the target tissue, the fungus begins to emit extensions called hyphae that correspond to its vegetative apparatus, following a typically radial growth (in all directions). All this framework gives rise to the milletium of the fungus that after a while bears fruit producing many spores. If it so happens that these fructifications occur in open wounds, the spores leave the fish and remain in the water column, at the mercy of another fish eating them and repeating the cycle.


As previously stated, it manifests itself externally by thinning, color change, etc., symptoms that can confuse us in the diagnosis because they are common to other conditions. Confirmation will only be possible through dissection and study of the internal organs.

As sick fish release spores with their droppings, the aquarium can quickly become contaminated if we do not take the precaution of isolating the sick fish at the slightest symptom. If Ichthyosporidium does not result, the isolation will not be harmful, but if a sick fish remains in the community aquarium, the consequences can be unpredictable.

There is no cure for this disease, at least with common fish medications. It is possible to avoid dissemination by using Ketoconazole (100 mg/10.57 gal) + Bactron (1 tab/7.93 gal) renewing 50% every 48 hours… use at least 7-10 days.

An alternative treatment would be with Tetracycline in 500mg tablets. The daily dose is 500 mg per 13.20 gal of water. Change 25% of the water every day. For 3 to 5 days.

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