Antagonism between parasites within snail hosts impacts the transmission of human schistosomiasis.

Human disease agents exist within complex environments that have underappreciated effects on transmission, especially for parasites with multi-host life cycles. We examined the impact of multiple host and parasite species on transmission of the human parasite in Kenya. We show is impacted by cattle and wild vertebrates because of their role in supporting trematode parasites, the larvae of which have antagonistic interactions with in their shared vector snails. We discovered the abundant cattle trematode, fails to develop in unless larvae are present in the same snail. Further development of is subsequently prevented by 's presence. Modeling indicated that removal of would increase -infected snails by two-fold. Predictable exploitation of aquatic habitats by humans and their cattle enable to exploit , thereby limiting transmission of this human pathogen.