Host–parasite interactions in polluted environments

In recent years, there has been an increasing number of papers showing how parasitism and pollution can interact with each other in aquatic organisms. In addition to synergistic negative effects of both stressors, there are also indications of antagonistic interactions. The latter are related to the reduction of pollutant levels in infected hosts compared with uninfected conspecifics. As reduced pollutant concentrations are usually correlated with less adverse effects, it might be advantageous to be infected if hosts are confronted with environmental pollution. On the other hand, possible pathological effects might reduce a potentially beneficial effect of parasites. There are also examples, however, which show that parasites may enhance toxic effects of pollutants by interfering with host‐protection mechanisms. In these cases, a parasitosis would have exclusively negative effects on the physiological homeostasis of their hosts. This presentation summarizes the current knowledge on interactions between parasites and pollutants with respect to their effects on the host’s health.