Paradoxically, several important human pathogens survive in the very cells equipped to kill them - the macrophages. Macrophages may thus provide unique environments that support intracellular survival and replication of pathogens. Pathogen growth is intimately linked to the ability to scavenge essential nutrients from the host. We provide evidence that this has led to the tropism of the protozoan parasite Leishmania to the highly lytic lysosomes of macrophages. Leishmania require sugars for survival in macrophages, however glucose levels within macrophage lysosomes are insufficient to support intracellular replication. We now show that Leishmania have access to amino sugars in macrophages and that intracellular parasites can utilize amino sugars as major carbon source. Macrophages readily take up and recycle extracellular cellular matrix polymers that are enriched in amino sugars. Leishmania are unable to utilize these polymers directly, but rather depend critically on host enzymes to generate free amino sugars. Given that this enables Leishmania growth in macrophages and to cause disease in animals, we propose a novel strategy to target intracellular pathogens.