Most ecosystems are exposed to multiple stressors acting in concert and their combined effects on para-site prevalence in freshwater, marine and terrestrial habitats are largely unknown. We investigated therelationships between farming intensity, water abstraction intensity and parasite prevalence in the mudsnail Potamopyrgus antipodarum from 20 stream sites within the Manuherikia River catchment (NewZealand) by using generalized linear models and an information-theoretic model-selection approach.Three trematode taxa that use water birds as definitive hosts were found in the snail host. The averageprevalence of all parasites infecting Potamopyrgus in the catchment was 5%. Microphallus sp. “lively”,the most common parasite, was most prevalent at high farming intensity and low water abstraction,besides showing an antagonistic interaction between the two agricultural stressors. These findings high-light the importance of considering multiple stressors and their potential interactions when studyinghost–parasite systems. Because snails often play key roles in aquatic communities, providing an impor-tant link between primary producers and higher trophic levels, and are a common intermediate hostto a high diversity of trematode parasites, this host–parasite model system may represent a promisingbioassessment tool for detecting anthropogenic disturbances in freshwater systems.