Alterations in the Kidney and Liver Histoarchitecture of Nile Tilapia Oreochromis niloticus upon Prolonged Oral Oxytetracycline Administration

Antibiotics are essential for specific and diagnosed practices in aquaculture practices and many of them are toxic to fish if abused. This study reports the effects of prolonged use of dietary oxytetracycline at 0-10 times the therapeutic dose (×: 80 mg/kg biomass/day) on the kidney and liver histoarchitecture of Oreochromis niloticus. A dose-dependent reduction in feed intake, survival and biomass were noticed on day 30 of dosing. The major histopathological changes found in the kidney were degeneration of renal tubular epithelium, vacuolation, inflammation, widened lumen, nephrocalcinosis, necrotized haematopoietic area, glomerulopathy with dilated Bowman’s space and thickening of lumen lining. The liver exhibited dose-dependent mild to marked glycogen-type hepatocellular vacuolation, cytoplasmic degeneration and cellular hypertrophy. Mild lipid-type vacuolations were present in the 5× and 10× groups. The suspension of dosing demonstrated only an insignificant recovery capacity of dosed O. niloticus for a prolonged period, which is a cause for concern.