ABCB1 and infection: Subsequent analyses revealed a correlation between pre-ivermectin treatment L. loa microfilarial density and the risk of developing a serious neurological adverse event.9,10 The mechanism of these events has been debated in the literature, largely focusing on the role of concomitant high burden infection with L. loa versus the presence of mdr-1 gene variants in humans allowing ivermectin penetration into the central nervous system (CNS).11,12