About the Elimination of onchocerciasis in Côte D'Ivoire: Potential frontline localities in the aboisso region

Objective: To highlight the agglomerations where the risk of transmission of onchocerciasis is highest in the region of Aboisso, with a view to eliminating this endemic in Côte d'Ivoire. Methods: Entomological surveys were carried out in the Aboisso region in the south-east of Côte d'Ivoire, in the forest zone, during the last semester of 2013 (from 2 July to 27 December). These surveys are part of a better knowledge of the status of onchocerciasis transmission in Côte d'Ivoire. The investigations took place at a time when the distribution of ivermectin had just been severely disrupted throughout the country, after six years of application. Thus, breeding places of Simulium damnosum s.l were prospected in the rivers of the main watersheds, the aggressiveness parameters of the populations of this complex were determined and the transmission of onchocerciasis was evaluated in the Aboisso region. Finding: Only 23.33% of the potential breeding places hosted preimaginal stages of Simulium damnosum s.l. These preimaginal stages were mostly collected in the Bia river and its tributaries (49.20%), as well as in the Noé river (15.11%). The monthly bite rate (MBR) for females fluctuates from 4.86 p/H/h to 124.24 p/H/h and the annual bite rate (ABR) varies from 58.27 p/H/year to 1,490.86 p/H/year. In the experimental area, each person receives approximately 1 to 17 bites every hour from 7 a.m. to 6 p.m. The highest rate of aggressiveness of Simulium damnosum s.l. (1490.86 p/H/year) was recorded in Bianouan. The annual potential for transmission (APT) is zero in the experimental area as none of the blackfly females dissected carried an infective stage of Ochocerca volvulus. Conclusion: Thus, the risk of transmission of onchocerciasis is non-existent at Aboisso, providing in this additional evidence of the efficacy of the control of this infection through treatment with ivermectin under community guidelines (CDTI). In addition, the annual bites rate (ABR) of females of Simulium damnosum s.l determined, argues in favor of a focus of the fight towards the elimination of onchocerciasis in the region. In the latter case, the village of Biaka, the N'guessan Assamoikro Camp in Bianouan and the locality of Kotoka, which are located near Simulium damnosum s.l. breeding places, appear as localities that can constitute first-line villages. To be able to easily establish the phase of elimination of onchocerciasis in Côte d'Ivoire, such a study should be undertaken on the whole of ivorian territory in order to updat the data on the preimaginal breeding places of S. damnosum s.l. which indeed date from the period of the OCP.