Iodophor Disinfection of Walleye Eggs Exposed to Viral Hemorrhagic Septicemia Virus Type IVb

Abstract

AbstractTwo experiments were performed to determine the persistence of viral hemorrhagic septicemia virus (VHSV) genotype IVb on Walleye Sander vitreus eggs. Fertilized Walleye eggs were exposed for 30 min to 105 plaque‐forming units/mL VHSV genotype IVb, and control eggs were exposed to phosphate‐buffered saline. In the first experiment, the eggs were treated with 0 and 50 mg/L iodophor and incubated at 12±1°C until the first fry emerged. In the second experiment, a treatment of 100 mg/L iodophor was also tested. Periodic samples were taken during embryo development and tested for VHSV by viral isolation and quantitative reverse‐transcription polymerase chain reaction (qRT‐PCR). The effect of tannic acid, an inhibitor of qRT‐PCR testing, was evaluated in the second experiment. In both experiments no virus was detected in any control eggs by either test. In the first experiment, virus was isolated in 0‐mg/L iodophor‐treated eggs up to 3 d postinfection (DPI). Virus was also isolated in the 50‐mg/L iodophor‐treated group at 1 DPI. Testing by qRT‐PCR detected viral RNA at all time points throughout the first experiment. In the second experiment, no VHSV was isolated after the initial 0‐DPI sample. Viral RNA was again detected at all time points, including samples collected at the end of the experiment. Inhibition was found in 34 of 36 samples at 0 DPI and 21 of 36 samples at 1 DPI. The number of inhibited samples decreased over time, but virus was still detected in three samples at 24 DPI. These experiments show that VHSV persists on Walleye eggs for longer than was previously known. At early time points VHSV was still detected despite disinfection, and viral RNA was detected at all time points; however, it is unknown whether the virus detected by this qRT‐PCR is viable. These experiments reinforce the need for careful disinfection of eggs.