Isolation, molecular identification, and pathological lesions of spp. isolated from common carp, in floating cages in Mosul, Iraq.

Background And Aim: Saprolegniasis is a fungal disease that infects freshwater fish. The condition is characterized by a cotton-like appearance in the gills and body. This study aimed to isolate from common carp, , raised in a floating cage in Wana district, Mosul, Iraq.

Materials And Methods: Samples were collected from 15 infected fish and examined microbiologically, molecularly, and histopathologically. DNA was extracted which was amplified using universal primers give a 540 bp DNA fragment, and gill and muscle tissue were also examined for histopathological changes.

Results: Isolated colonies of were characterized by a circular, white cottony appearance with long hair. Lactophenol staining demonstrated hyphae as branched non-septate, transparent masses. The genomic DNA of isolates was consistent with spp. The infected tissue samples showed variable pathology in gills. Severe hemorrhage and edema were observed in primary gill filaments with hyperplasia in epithelial cells and infusion in secondary gill filaments. Hyphae of were seen between necrotic and edematous myofiber with inflammatory cells infiltration.

Conclusion: can cause economic impacts through lethal infection of fish. Clinical signs of infection were confirmed molecularly and microscopically, and these findings were supported by histopathological lesions in gill and muscle tissues.