Ichthyophoniasis (Ichthyosporidiosis) - Fungal Diseases of Fish

Ichthyophoniasis (Ichthyosporidiosis)

CAUSATIVE AGENT:

Ichthyophonus sp. (=Ichthyosporidium sp.)

SPECIES AFFECTED:

Groupers, trouts, flounders, herrings and cods

GROSS SIGNS:

External manifestation of the disease varies from species to species, while some affected fish don’t show any external sign. Erratic swimming behavior and swelling of the abdomen are sometimes observed among affected fish. Internal organs (spleen, liver and kidney) become swollen with numerous whitish nodules up to 2 mm diameter. Nodules can also be observed in the muscle tissues of some affected fish.

EFFECTS ON HOST:

Infected fish lose their appetite and become lean and anemic.

DIAGNOSIS

The nodules formed in internal organs or muscle will show different stages of the pathogen (early cyst stage, developed cysts, fungal hyphae) when observed under the microscope. These are surrounded by the hosts’ connective tissues

forming lumpy granulomas which are typical of a fungus-infected tissue.

PREVENTION AND CONTROL:

There is no known treatment of ichthyophoniasis. Cultured fish become in-fected when they are fed raw trash fish contaminated with the pathogen. There-fore, contaminated trash fish should be carefully avoided to prevent outbreaks.