Malaria epidemiology in the Korhogo area, Northern Côte d'Ivoire: baseline assessment prior to a randomized controlled trial.

Abstract

Background: Widespread Insecticide resistance among malaria vector populations poses a significant threat to the efficacy of current vector control strategies. This highlights the urgent need for innovative approaches that integrate existing tools with those under development. The primary objective of this study was to characterize the malaria epidemiological profile in the Korhogo region prior to the implementation of complementary vector control tools alongside long-lasting insecticidal nets (LLINs). Both passive and active case detection methods were employed.

Methods: Passive case detection involved data collection from heath care facilities between July 2016 and July 2017, covering a total of 398,424 person-weeks from 26 villages in the Korhogo health district, northern Côte d'Ivoire. Active case detection was carried out through three cross-sectional surveys (CSS) conducted in September 2016, December 2016 and March 2017. During these surveys, individuals under 21 years of age were invited to attend clinical consultations. Those presenting with fever (> 37,5 °C) were tested for malaria with rapid diagnostic test (RDT), and individuals with a positive result were treated with artemisinin-based combination therapy (ACT). Active case detection during the surveys enabled the estimation of malaria case prevalence, defined as the proportion of population with symptoms and a positive RDT at the time of the survey. Additionally, in a randomly selected sub-sample of six villages, thick blood smears were analysed-regardless of symptoms-to assess the prevalence of malaria infection in the general population during CSS.

Results: The mean weekly malaria incidence throughout the year in the overall population was 0.25 cases per 100 person-weeks, corresponding to 130 cases per 1000 person-years. During CSS, malaria cases prevalence ranged from 13.4% during the dry season to 43.4% in the late rainy season. The highest malaria cases' prevalence was observed in children under 5 years of age, with significant decline in older age groups. Thick blood smears from six villages revealed parasite prevalence between 85.4% and 100%. Plasmodium falciparum accounted for 97% of single infection, although mixed infections with Plasmodium malariae and Plasmodium ovale were also detected.

Conclusion: Active case detection conducted through three transversal surveys indicates that the study area exhibits characteristics of malaria transmission hotspot. The region's dense hydrographic network provides a favourable ecological and epidemiological context for assessing additional vector control strategies to supplement universal LLINs coverage in the fight against malaria.