Onchocerciasis transmission in Kafolo, located in the Côte d’Ivoire – Burkina Faso cross-border region of Tchologo

Abstract

Abstract Background: Onchocerciasis or river blindness is a parasitic endemicity caused by a filariasis called Onchocerca volvulus. This nematode worm is transmitted to humans due to bites by infested female black flies. In 2002, WHO closed the Onchocerciasis control programme in West Africa at the time when the disease transmission risk was constricted in all countries where Onchocerciasis was a cause of concern. The aim of this study is to evaluate Onchocerciasis transmission in the Kafolo area, located at the Ivorian-Burkinabe border in the region of Tchologo in Côte d’Ivoire, after the period of interruption of the national Onchocerciasis control programme activities, and following the observation of an increase in the disease prevalence in both sides of the border. Methods: Standardized human landing catches of black flies based on a WHO/OCP technique were carried out in 2019 at the intervals of two (2) days per month. Caught black flies were dissected to look for potential onchocerca larvae. These larvae were then analyzed through the PCR technique 0 - 150 to identify their species. Results: Annual Bitting Rates (ABR) were 25,355 and 20,235 bites/person/year at Kafolo-Amont and at Kafolo-Aval respectively, with an average parturity rate of 60.33% at the level of the first site and 55.23% at the level of second one. Adjusted infectivity rates amounted to 3.93 IF/1,000 pares and 4.91 IL/1,000 pares for Kafolo-Amont (Upstream) and to 4.03 IF/1,000 pares and 6.71 IL/1,000 pares for Kafolo- Aval (Downstream). Adjusted ABR reported 75 bites/person/year in each site. This rate exceeds almost 4 times the threshold defined by WHO for the disease control. the high transmission rate observed in this study was not expected and could constitute a potential source of contamination of adjacent river basins across the border in Burkina Faso. Conclusion: There is active onchocerciasis transmission continues at Kafolo. Therefore, Onchocerciasis elimination is not yet achieved in this site. The subsequent recommendation is that entomological and epidemiological transmission prevalence data be updated in this area.