Susceptibility of Tilapia Lake Virus to buffered Povidone-iodine complex and chlorine

Abstract

Tilapia Lake Virus (TiLV) is an emergent orthomyxo-like virus affecting the global tilapia (Oreochromis sp.) aquaculture industry. Mortality in affected farms can reach 80–90% in severe outbreaks. Effective vaccines and chemotherapeutic treatments are currently unavailable. The aim of this study was to identify the virucidal efficacy of two commonly used disinfectants, namely household bleach (free-chlorine) and a Buffered Povidone-iodine (PVP Iodine) complex, against TiLV. An archived TiLV isolate was cultured on an endothelial Oreochromis mossambicus bulbus arteriosus cell line (TmB). Bleach and PVP ranging from 10 to 100 mg/L (ppm) were diluted the day of the assay in autoclaved well water collected from an aquaculture facility in California, USA and added to TiLV cultures for 0.5, 1, or 24 h. At each respective timepoint, sodium thiosulphate or fetal bovine serum were added to inactivate the available iodine and free chlorine, respectively. All aliquots were then titrated on TmB cells to determine the TCID50/ml. Virucidal reductions in titer >4 log10 TCID50/ml were obtained with ≥20 ppm free chlorine and ≥ 50 ppm available iodine after just 30 min contact time. When contact time was increased to 24 h, ≥10 ppm free chlorine and ≥ 25 ppm available iodine were required to achieve virucidal reductions in titer >4 log10 TCID50/ml. This information should be taken into consideration when developing biosecurity protocols in tilapia aquaculture to prevent the spread of TiLV.