Sterol 14alpha-demethylase (CYP51) is one of the enzymes in the sterol biosynthesis pathway, and the target of significant drug development research in Leishmania. Here we use a double approach to determine whether this gene is essential in Leishmania donovani, the causative agent of visceral leishmaniasis. Here, CYP51A1 is linked to visceral leishmaniasis.