Why Does Malaria Remain Endemic in Nigeria Despite Proven Interventions?

A Mathematical Modeling Approach to Identify the Missing Link to Elimination

Abstract

Background

Nigeria accounts for the largest share of the global malaria burden, with 27% of cases and 32% of deaths worldwide [1]. Despite large-scale deployment of insecticide-treated nets, indoor residual spraying, seasonal malaria chemoprevention, and intermittent preventive treatment in pregnancy, transmission persists at high levels. This study used a Nigeria-specific mathematical model to investigate the “missing links” to malaria elimination.

Methods
We developed an age-structured SEIR-SEI model parameterized with Nigeria-specific epidemiological and intervention coverage data [2,3]. Intervention efficacy was adjusted for insecticide and drug resistance. Four scenarios were simulated over a two-year horizon: (i) baseline (status quo coverage), (ii) scale-up (world health organization target coverage levels), (iii) resistance-mitigated (higher efficacy of insecticide-treated nets, indoor residual spraying, and anti-malaria medication), and (iv) asymptomatic reservoir targeted (mass drug administration/active detection). Outcomes were age-specific infectious prevalence, vector prevalence, and incidence. Global sensitivity analysis using Latin Hypercube Sampling and Partial Rank Correlation Coefficients was conducted to assess parameter influence.

Results
Under baseline conditions, mean infectious prevalence was 7.7% in children and 4.5% in adults, with 21.3% of mosquitoes infectious, sustaining 405 new infections/day in the modeled population. Scale-up reduced prevalence in children (36%) and adults (25%), but incidence remained unchanged. Resistance mitigation achieved similar prevalence reductions but only marginal incidence impact (1%). Asymptomatic clearance achieved the largest short-term prevalence reduction (60% in children, 54% in adults), but incidence rebounded as transmission re-established. Sensitivity analysis identified insecticide-treated nets and indoor residual spraying efficacy, treatment coverage, and vector biting rate as the most influential parameters.

Conclusions
Malaria persists in Nigeria not simply due to inadequate tools, but because of three missing links: (i) suboptimal effective coverage, (ii) insecticide and drug resistance, and (iii) asymptomatic reservoirs. Addressing these simultaneously, through improved use of preventive tools, rapid deployment of next-generation nets and and indoor residual spraying, strengthened anti-malaria drug stewardship, and strategies to detect and clear asymptomatic infections is essential for Nigeria to achieve elimination targets. Nigeria’s success or failure will define global malaria progress.