To determine whether IL-1β was involved in the genesis of chronic heart dysfunction in mice, we infected young Il-1r−/− and wild-type (WT) mice (24) (6–8 weeks old, C57BL/6 background) with the Colombian strain of T. cruzi and monitored parasitemia and weight gain during the acute and chronic stages of infection. The gene discussed is IL1B; the disease is parasitic infectious disease.