Tetracapsuloides bryosalmonae is a myxozoan endoparasite causing the Proliferative Kidney Disease (PKD) in salmonids. The disease is a wide spread disease affecting salmonids in the northern hemisphere. Its lifecycle includes two hosts, a freshwater bryozoan and brown trout. The parasite transmits between hosts via spores released into water. In this study, influence of waste water treatment plants (WTPs) was investigated by measuring the eDNA (DNA from a water sample) concentration in Swiss rivers up- and downstream of WTPs. Sample analysis showed that parasite eDNA concentration was significantly higher downstream from the WTP. Further correlation tests suggest that higher bryozoan biomass and infection severity cause this effect.