Effects of Bacterial-Fungal Coinfection on Biochemical Parameters and Organ Structure in African Catfish (Clarias gariepinus)

Five infected African catfish (605±45.98 g) from the Experimental Aquaculture Base at Trakia University exhibited abnormal behaviours, including sluggish movements, lethargy, skin haemorrhages, and fin bleeding. Samples from the lesions were cultured on Sabouraud Dextrose Agar (SDA), and the fungus was identified as Rhizopus sp. based on colony morphology and microscopy. Bacteriological samples from the kidney, spleen, liver, and blood were cultured on Tryptic Soy Agar (TSA) and Brain Heart Infusion Agar (BHIA), revealing the presence of Yersinia ruckeri, Aeromonas hydrophila, and Pseudomonas aeruginosa based on their physiological, morphological, and biochemical traits. Significant differences (p<0.01) were observed in the serum protein profiles, including total protein, albumin, globulin, and glucose levels. Histological examination showed pathological changes in the liver, kidneys, and gills, as well as haemorrhages and polymorphonuclear leukocyte infiltration in the skin lesions, with intense muscle necrosis. These biochemical and histopathological findings are valuable for monitoring health and diagnosing fungal diseases in African catfish.