Loiasis is endemic in the Ndikinimeki Health District (Centre Region, Cameroon) but does not represent a hindrance to onchocerciasis elimination

•The long-term impact of CDTI on the risk of SAEs was assessed in the Ndikinimeki Health District;•Calibrated thick blood smears were prepared for quantitation of Loa loa microfilariae;•Prevalence and intensity of L. loa infection are very low, below at risk level for post-ivermectin SAEs•Loiasis does not represent a hindrance to onchocerciasis elimination in the Ndikinimeki health district Community-Directed Treatment with Ivermectin (CDTI) is the strategy of choice to fight onchocerciasis in Africa. In areas where loiasis is endemic, onchocerciasis control and/or elimination is hindered by severe adverse events (SAEs) occurring after ivermectin mass treatments. This study aimed at (i) investigating the impact of two decades of CDTI on L. loa clinical and parasitological indicators in the Ndikinimeki Health District, and (ii) assessing the risk of SAEs after this long-term preventive chemotherapy. A cluster-based cross-sectional survey was conducted in the six Health Areas of the Ndikinimeki Health District. All volunteers underwent day-time calibrated thick blood smears to search for L. loa microfilariae, as well as an interview to assess the history of migration of eye worm and Calabar swelling. The overall prevalence of L. loa microfilaraemia was 2.2 % (95% CI: 1.3–3.7%), and the proportions of individuals who had already experienced eye worm and/or Calabar swelling were 1.0% and 0.5%, respectively. The mean microfilarial density was 63.55 (SD: 559.17; maximum: 9220.0) mf/mL. These findings indicate that (i) the long-term ivermectin-based preventive chemotherapy against onchocerciasis significantly reduced L. loa clinical and parasitological indicators, and (ii) the risk of developing neurologic and potentially fatal SAE after ivermectin mass treatment is zero in the Ndikinimeki Health District.