Role of Silver Nanoparticles Synthetized by Marine Red Algae, Acanthophora spicifera, Against Saprolegniosis in Oreochromis niloticus

Abstract

The anti-fungal activity of Acanthophora spicifera-synthetized silver nanoparticles (AS-AgNPs) was tested in vitro against S. australis. In vivo, 160 Oreochromis niloticus (25 ± 0.57 grams) were separated into 4 groups; group 1 and group 2 received 0 mg/L and 0.9 mg/L AS-AgNPs, respectively, and were not exposed to S. australis. Group 3 and group 4 were experimentally infected with S. australis and imperiled to 0 and 0.9 mg/L AS-AgNPs for 96 hours, respectively. At all levels, survival rates, non-specific immune indices, antioxidant activities, and expression analysis of IL-8 and TNF-α genes in the anterior kidneys were estimated. Moreover, histopathological pictures of the skin and underlying musculature were investigated. Results showed that AS-AgNPs produced an inhibitory zone with a diameter of around 12 millimeters. A significant survival rate (72.50%) accompanied by marked non-specific immune responses and antioxidant activities was recorded in the infected-treated group. The histopathological picture of the skin and underlying musculature of diseased fish (group 3) exhibited degenerative changes in the dermal and epidermal layers of the skin and the myocytes. Intriguingly, infected fish treated with AS-AgNPs (group 4) showed normal histological structures of the skin and underlying musculature. Based on these findings, AS-AgNPs have a curative outcome against the destructive effects of S. australis infection and are a potential option for the control of S. australis infection in aquaculture.