Pathogenicity of Aspergillus fumigatus in Experimental Infection of Different Developmental Stages of Clarias gariepinus

Aims: This study aimed to investigating the pathogenicity of Aspergillus fumigatus in the experimental infection of Clarias gariepinus fingerlings and juvenile catfish. Experimental Procedure: Aspergillus fumigatus used for this study was isolated from the gills and liver of infected juveniles presented for microbial diagnostic examination, cultured on Sabouraud dextrose agar for 3 – 4 days, and identified at the Aquatic Animal and Wildlife Laboratory (AAWL), Department of Veterinary Medicine, University of Ibadan. Methodology: One hundred and forty healthy eight-week old Clarias gariepinus fingerlings (average weight of 4g) and 140 healthy sixteen-week old juvenile (average weight of 10g) were purchased from a commercial fish farms in Ibadan. The fingerlings and juveniles were randomly divided into seven groups, each with 20 fish in five litters of water. The fungal suspension containing 3.2 X 106 spores/ml of Aspergillus fumigatus was used for the pathogenicity test. Six groups were infected by immersion in water containing fungal spores at the rates of 2ml/L and 5ml/L for fingerlings and juveniles respectively. The clinical signs, skin lesions and mortality were observed daily for 14 days. Results: Aspergillus fumigatus isolated in this study has green spiked conidia; and the size of the conidia is 2.5µm. The conidia have a smooth surface and small spikes covering their surface. Moreover, the mortality rate was significantly (p = 0.40) higher in infected fingerlings (80%) than juveniles (62%) at fourteen days post-infection. The gross lesions observed during experimental infection of fingerlings and juveniles included exophthalmia, atrophied barbel, congested trunk kidney, hyperemia of gill filaments, and skin depigmentation. The histopathological organ changes caused by Aspergillus fumigatus were obvious in the liver and gills. Vacuolar degeneration of hepatocytes and necrosis of some melanomacrophage cells, in addition, severe erosion of the primary and secondary lamellae, were observed in infected juveniles. Conclusion: Aspergillus fumigatus causes high mortality in fingerlings and juvenile of African Catfish (Clarias gariepinus).