Over a decade of seasonal malaria chemoprevention in Békourou in Chad: How effective is it today?

Since 2013, seasonal malaria chemoprevention (SMC) has been implemented in the Moïssala and Békourou health districts of Chad by Doctors Without Borders (MSF), in collaboration with the Ministry of Public Health and the National Malaria Control Program (PNLP). This strategy aims to protect children aged 3 to 59 months by administering a combination of sulfadoxine-pyrimethamine and amodiaquine to them every month during the rainy season, when the risk of malaria is highest.

Recommended by the World Health Organization since 2012 in areas with high seasonal transmission, SMC has established itself as one of the most effective interventions for reducing the incidence of malaria among young children.  

A strategy monitored and evaluated over the long term

Since the program’s inception, Epicentre has supported its implementation through various studies designed to measure its impact, identify challenges, and guide its adaptation. This work has notably helped adjust the duration and timing of SMC cycles to improve their effectiveness in the local context.

At the same time, Epicentre is monitoring changes in molecular markers associated with resistance to the drugs used in the SPAQ combination. This monitoring is essential, as the large-scale use of antimalarial drugs can promote the emergence of Plasmodium falciparum strains that are less sensitive to treatment.

Signs to watch for

“Three studies conducted between 2014 and 2023 tracked the evolution of several genetic mutations associated with reduced efficacy of sulfadoxine-pyrimethamine,” explains epidemiologist Francesco Grandesso. The results show a significant increase in the frequency of the quadruple mutation (dhfr N51I, dhfr C59R, dhfr S108N, and dhps A437G), which rose from 28% in 2014 to 48% in 2023. However, the quintuple mutation, which includes the dhps K540E mutation that is a key indicator of resistance to sulfadoxine-pyrimethamine, remained low and relatively stable, with a prevalence ranging from 3% to 8%.”

At the same time, surveillance data indicate that SMC continues to yield significant benefits. The incidence of clinical malaria among children under five remained consistently lower during the years when SMC was implemented than in 2019, when the intervention was not implemented.

A new study to measure the actual effectiveness of SPAQ

Despite these encouraging results, the increase in resistance-associated mutations and more than ten years of continuous use of the SPAQ raise important questions about its long-term preventive and therapeutic effectiveness.

To address these questions, Epicentre is currently conducting a prospective cohort study in the Békourou health district. The objective is to evaluate the in vivo effectiveness of the SPAQ combination among children participating in routine SMC.

“In particular, we will analyze the SPAQ’s ability to eliminate pre-existing, low-intensity asymptomatic parasitemia and to prevent the onset of new malaria infections during the 28 days following its administration. The study will thus help document the potential impact of changes in genetic markers of resistance on the preventive and therapeutic effectiveness observed in the field,” explains Paulina Jedynak, an epidemiologist in charge of implementing this study in Chad.

Expected results to guide future strategies

The results of this study will help evaluate the effectiveness of the SPAQ and provide concrete evidence to national and international decision-makers.

“If the effectiveness of SPAQ remains satisfactory, these data will support its continued use in SMC programs,” analyzes Francesco Grandesso. Conversely, a decline in its performance could justify a transition to other chemoprevention strategies in the affected areas.” Among the alternatives currently being studied is the dihydroartemisinin-piperaquine (DHA-PPQ) combination.

An issue that extends beyond Chad

The significance of this research extends beyond the Chadian context. The SPAQ-based SMC is currently deployed in many sub-Saharan African countries facing comparable malaria transmission dynamics.

In this context, monitoring the emergence and spread of molecular markers of resistance is a major challenge for preserving the effectiveness of an intervention that protects millions of children each year. The results of this study could thus help inform future WHO recommendations, guide resistance surveillance strategies, and inform decisions regarding the adaptation of SMC throughout the Sahel region and in sub-Saharan Africa.

© Paulina JEDYNAK