Date Published: February 18, 2018
Publisher: The American Society of Tropical Medicine and Hygiene
Author(s): Thomas Druetz, Nicolas Corneau-Tremblay, Tieba Millogo, Seni Kouanda, Antarou Ly, Abel Bicaba, Slim Haddad.
Seasonal malaria chemoprevention (SMC) for children < 5 is a strategy that is gaining popularity in West African countries. Although its efficacy to reduce malaria incidence has been demonstrated in trials, the effects of SMC implemented in routine program conditions, outside of experimental contexts, are unknown. In 2014 and 2015, a survey was conducted in 1,311 households located in Kaya District (Burkina Faso) where SMC had been recently introduced. All children < 72 months were tested for malaria and anemia. A pre–post study with control group was designed to measure SMC impact during high transmission season. A difference-in-differences approach was coupled in the analysis with propensity score weighting to control for observable and time-invariant nonobservable confounding factors. SMC reduced the parasitemia point and period prevalence by 3.3 and 24% points, respectively; this translated into protective effects of 51% and 62%. SMC also reduced the likelihood of having moderate to severe anemia by 32%, and history of recent fever by 46%. Self-reported coverage for children at the first cycle was 83%. The SMC program was successfully added to a package of interventions already in place. To our knowledge, with prevalence < 10% during the peak of the transmission season, this is the first time that malaria can be reported as hypo-endemic in a sub-Sahelian setting in Burkina Faso. SMC has great potential, and along with other interventions, it could contribute to approaching the threshold where elimination strategies will be envisioned in Burkina Faso.
Despite encouraging signs of a recent reduction in transmission,1,2 malaria remains one of the most important public health problems in Burkina Faso. Its entire population lives in high-risk transmission areas. The 2015 World Malaria Report indicates that there were 5,428,000 confirmed cases and 17,000 deaths attributable to malaria out of a total population of 17 million, and the latest malaria indicator surveys revealed a parasitemia prevalence (detected by microscopy) of 46% in children 6–59 months.3 With 414 malaria cases per 1,000 persons at risk, Burkina Faso has one of the highest incidence rates in the world.4 Most of the malaria cases and deaths occur during or directly after the rainy season (approximately from July to October) and children < 5 are at the greatest risk; surveillance data indicate that they represented 51% of all malaria cases and 69% of all deaths attributable to malaria in 2016.5–9 It has been estimated that ∼20,000 deaths and 5 million cases of malaria could be averted with SMC in the Sahel and sub-Sahel regions, if this intervention were widely deployed.12 However, the extent of the potential impact is contingent on the coverage and effectiveness that nationwide programs could achieve. This is the first study to evaluate the impact and coverage of a large-scale SMC program under routine program implementation. SMC had immediate and significant protective effects for the four malaria-related outcomes. It significantly reduced the prevalence of malaria and anemia among the population, as well as the occurrence of fever episodes. The robustness of the design, and the congruency of the results over the different outcomes and analytical approaches, substantiate our assertion that SMC had a significant (clinically and statistically) positive impact on child morbidity in the study area. The point prevalence of malaria was reduced by 3.3% points (95% CI = [−0.08 to 0.01]), which translated into a protective effect (adjusted risk ratio) of 51% (95% CI = [0.24–0.99]). The protective effect on the period prevalence was larger, 62% (95% CI = [0.29–0.52]). This is unexpected because HRP2-based RDTs take more time to turn negative after parasite clearance than pLDH-based RDTs, and therefore are less sensitive to measure SMC therapeutic effect between two cycles.44,45 A plausible explanation is that a floor effect occurred, as the overall point prevalence of malaria was already low in the study area. This may have contributed to making the evaluation of impacts less precise and reducing the power of statistical tests, as shown by the large 95% CI = for this particular outcome. During the first year of its introduction under routine program conditions, SMC already had large and positive impacts for the targeted population. The prevalence of all malaria-related outcomes under study (malaria parasitemia, moderate to severe anemia, and occurrence of febrile episodes) decreased immediately after the first cycle of the SMC campaign. This translated into large and significant protective effects for the children who received the chemoprevention treatment. SMC was successfully added to the package of interventions already in place in the health district where the study was conducted, even if some implementation barriers, notably limited coverage, likely reduced its effectiveness. To our knowledge, it is the first time that malaria can be described as hypo-endemic in the area, with a parasitemia prevalence < 10% during the peak of its transmission season. SMC is an intervention with great potential in Burkina Faso, and along with other interventions, it could contribute to approaching the threshold where elimination strategies will be envisioned. Source: http://doi.org/10.4269/ajtmh.17-0599