In order to evaluate how the inter-strain diversity observed so far impacts on the course of in vivo infection, we infected C57BL/6 wild-type mice as well as mice deficient in the antimicrobial enzymes phagocyte NADPH oxidase (p47phox−/−) and nitric oxide synthase 2 (Nos2−/−) with each of the described L. infantum strains and the number of parasites in their livers and spleens were quantified after 15 and 60 days of infection. The gene discussed is NCF1; the disease is infection.