Waluga D., Własow T., Dyner E., Świątecki A., 1986. Studies on the etiopathogenesis of fish diseases in the Baltic Sea. Acta Ichthyol. Piscat. 16 (2): 53-72.

An invasion of microsporidia from the genus Pleistophora was discovered in cod, herring, sprat and flounder. The invasion was very intensive and it was considered as one of the reasons of fish diseases in the Baltic Sea. Accompanying infection of mixed bacterial flora complicated and enhanced the disease process. Development of the disease was also induced by weak natural resistance of the fishes, this being due to pollution of the Baltic Sea.