Ichthyosporidiosis Exophiala sp. Saprolegniasis affects all species and ages of freshwater and estuarine fish . Clinically, affected fish develop white to brown cotton-like growths on skin, fins, and gills. This organism is an opportunist which will usually grow over previous ulcers or lesions. Diagnosis is by finding nonseptated branching hyphae that produce motile flagellated zoospores in the terminal sporangia.
Most fish die due to osmotic or respiratory problems if the area of skin or gills is large.
The fungi are normal water inhabitants that invade the traumatized epidermis. Improper handling, bacterial or viral skin diseases, and trauma are the major causes of the disease. It is interesting to note that temperature has a significant effect on the development of infections. Most epizootics occur when temperatures are below the optimal temperature range for that species of fish. Caused by two species Branchiomyces sanguinis and B. demigrans.