Strikingly, following infection with S. mansoni, CAT2−/− mice developed parasite egg–induced lesions in the liver that were 3 to 4 times larger than wild type and hepatic fibrosis (a feature of severe schistosomiasis) was exacerbated, indicating a general worsening of disease in the absence of CAT2. Here, SLC7A2 is linked to schistosomiasis.