Introduction: Despite the implementation of control strategies at the national scale, the malaria burden remains high in Mali, with more than 2.8 million cases reported in 2019. In this context, a new approach is needed, which accounts for the spatio-temporal variability of malaria transmission at the local scale. This study aimed to describe the spatio-temporal variability of malaria incidence and the associated meteorological and environmental factors in the health district of Kati, Mali. Methods: Daily malaria cases were collected from the consultation records of the 35 health areas of Kati’s health district, for the period 2015–2019. Data on rainfall, relative humidity, temperature, wind speed, the normalized difference vegetation index, air pressure, and land use–land cover were extracted from open-access remote sensing sources, while data on the Niger River’s height and flow were obtained from the National Department of Hydraulics. To reduce the dimension and account for collinearity, strongly correlated meteorological and environmental variables were combined into synthetic indicators (SI), using a principal component analysis. A generalized additive model was built to determine the lag and the relationship between the main SIs and malaria incidence. The transmission periods were determined using a change-point analysis. High-risk clusters (hotspots) were detected using the SatScan method and were ranked according to risk level, using a classification and regression tree analysis. Results: The peak of the malaria incidence generally occurred in October. Peak incidence decreased from 60 cases per 1000 person–weeks in 2015, to 27 cases per 1000 person–weeks in 2019. The relationship between the first SI (river flow and height, relative humidity, and rainfall) and malaria incidence was positive and almost linear. A non-linear relationship was found between the second SI (air pressure and temperature) and malaria incidence. Two transmission periods were determined per year: a low transmission period from January to July—corresponding to a persisting transmission during the dry season—and a high transmission period from July to December. The spatial distribution of malaria hotspots varied according to the transmission period. Discussion: Our study confirmed the important variability of malaria incidence and found malaria transmission to be associated with several meteorological and environmental factors in the Kati district. The persistence of malaria during the dry season and the spatio-temporal variability of malaria hotspots reinforce the need for innovative and targeted strategies.

Background: WHO and its partners have adopted alternative control interventions since the failure to eradicate malaria worldwide in the 1960s and 1970s. The aim of these interventions has been to redesign the control interventions to make them more effective and more efficient. The purpose of this study is to assess the population impact of control interventions implemented at the community health area level. Methods: The analysis used data from the health information system on malaria cases and interventions (distribution of long-lasting insecticide-treated nets (LLINs), seasonal malaria chemoprevention (SMC), access to rapid diagnostic tests (RDT), intermittent preventive treatment for pregnant women (IPTp)) collected in the Kati health district from 2017 to 2020. And the contextual parameters (temperature, normal difference vegetation index (NDVI) and rainfall) were obtained by remote sensing. A generalized additive model was used to assess the impact of malaria control interventions on malaria cases as a function of meteorological factors. Results: The incidence of malaria varies from year to year and from health area to health area, as do meteorological factors in the study area. The distribution of long-lasting insecticide-treated nets, chemoprevention of seasonal malaria in children and access to rapid diagnostic tests for malaria were found to have a significant impact on the incidence of malaria in the population. Seasonal malaria chemoprevention was effective in reducing the incidence of malaria, while distribution of long-lasting insecticide-treated nets and access to rapid diagnostic tests increased with the number of malaria cases, reflecting efforts to distribute and use bed nets and to diagnose malaria cases among the population in the study area. Conclusion: The study showed the impact of SMC on reducing malaria cases in the population and the significant efforts in LLIN distribution and malaria case diagnosis. To further reduce the burden of malaria, sustained efforts and new interventions are needed, including improving access to rapid diagnosis and treatment in communities by developing community health workers and locally tailored mass drug administration.

The interpretation of a laboratory test result requires an appropriate reference range established in healthy subjects, and normal ranges may vary by factors such as geographic region, sex, and age. We examined hematological and clinical chemistry parameters in healthy residents at two rural vaccine trial sites: Bancoumana and Doneguebougou in Mali, West Africa. During screening of clinical studies in 2018 and 2019, peripheral blood samples from 1,192 apparently healthy individuals age 6 months to 82 years were analyzed at a laboratory accredited by the College of American Pathologists for a complete blood count, and creatinine and/or alanine aminotransferase levels. Based on manufacturers’ reference range values, which are currently used in Malian clinical laboratories, abnormal values were common in this healthy population. In fact, 30.4% of adult participants had abnormal neutrophil levels and 19.8% had abnormal hemoglobin levels. Differences by sex were observed in those who were older, but not in those younger than 10 years, for several parameters, including hemoglobin, platelet, and absolute neutrophil counts in hematology, and creatinine in biochemistry. The site-specific reference intervals we report can be used in malaria vaccine clinical trials and other interventional studies, as well as in routine clinical care, to identify abnormalities in hematological and biochemical parameters among healthy Malian trial participants.

Introduction: Seasonal malaria chemoprevention (SMC) reduces malaria incidence in children under five in Sahelian countries. However, transmission persists at substantial levels and incidence is re-increasing. Addressing Plasmodium falciparum carriage in asymptomatic individuals could represent a relevant intervention to complement current access to care- and vector-control-based strategies. In this study, we aim to characterise the parasite reservoir dynamics over one year in the general population of two sites of central and northern Mali. Methods: We included members of randomly selected households in four villages (2 in Kati and 2 in Dire districts). At four planned visits, infection was detected using rapid diagnostic tests (RDTs) and qPCR. Clinical malaria incidence was recorded passively at local health facility and Plasmodium positive samples were genotyped. We analyse clinical malaria incidence, P. falciparum PCR prevalence, parasite density and multiplicity of infection (eMOI) at different seasons, as well as factors associated with P. falciparum carriage. Results: Malaria seasonal dynamics was driven by rainfall in Kati (Central Mali) and by flooding in Dire (Northern Mali). In Kati, prevalence rose from 21.5% at the dry season 2021 baseline to 33.5% in December after the rainy season. Prevalence was lowest in SMC-eligible children across 3 of 4 surveys. Prevalence was highest (40-50%) for 10-24 years old in December. Median parasite densities were generally <10 parasites/µL except for 10-24 years old, who also presented higher eMOI. In Dire, prevalence was high at both baseline and December survey (60%) but dropped in September and in May 22. SMC was not distributed in 2021, and prevalence was homogenously high (50-70%) across groups in December. Parasite densities and eMOI fluctuated strongly across age-groups and survey. Discussion: Our findings show that in the “classic” Sahelian, rainfall-driven setting of Kati, a high prevalence of asymptomatic infections among 10-24 year-olds likely represents the reservoir for transmission. In the understudied Northern Mali, our results suggest generalized high burden and complex dynamics. Continuous SMC modifies the age-distribution of the parasite reservoir. Targeting asymptomatic carriers beyond SMC coverage could represent a relevant strategy to further reduce transmission in seasonal settings.