Susceptibility of Nanophyetus salmonicola cercariae to formalin, hydrogen peroxide and seawater

The ability of formalin, PEROX-AID® (hydrogen peroxide), and seawater to kill waterborne Nanophyetus salmincola cercariae was evaluated in vitro. Newly emerged waterborne cercariae survived for extended periods in freshwater, with 50-74% survival occurring in negative control groups after 24 hr. Exposure to dilutions of formalin reduced this survival time, with 0% of cercariae surviving after 30 min. in 167 ppm, 40 min. in 83 ppm, and 180 min. in 42ppm. Exposure to PEROX-AID® (hydrogen peroxide) for one hour resulted in reduced cercariae survival (16.4%) only at the highest concentration (100 ppm), compared to 100% survival in the untreated controls and all lesser concentrations. Dilutions of seawater resulted in reduced cercariae [...]