Narasin is a polyether carboxylic ionophore agent that is authorised in Europe according to Commission Regulation No (EC) 1464/2004 as a coccidiostat for use in chickens for fattening with a maximum content of the active substance in feed of 70 mg/kg and a withdrawal period of one day. Narasin is the active ingredient in Monteban, a premix that is incorporated into chicken feed. Narasin is already approved for continuous oral use as Monteban (NADA 118-980) in chicken feed for the prevention of coccidiosis at doses up to 80 mg narasin/kg feed. Narasin is produced by the fermentation of a strain of Streptomyces aureofaciens.The biological activity of narasin is based on its ability to form lipid soluble and dynamically reversible complexes with cations, preferably monovalent cations such as alkaline K+, Na+ and Rb+: Narasin functions as a carrier of these ions, mediating an electrically neutral exchangediffusion type of ion transport across the membranes. The resultant changes in transmembrane ion gradients and electrical potentials produce critical effects on cellular function and metabolism of coccidia. Narasin is effective against sporozoites and early and late asexual stages of coccidia in broilers caused by Eimeria acervulina, E. brunetti, E. maxima, E. mivati, E. necatrix and E. tenella. Narasin also is used for prevention of necrotic enteritis in broiler chicken. Narasin was identified and characterized as a novel agent that inhibits DENV replication in vitro through non-cytotoxic mechanisms, thus indicating its potential to be further developed as a therapeutic anti-DENV agent.