Trends in malaria epidemiological factors following the implementation of current control strategies in Dangassa, Mali

Abstract

Background Over the past decade, three strategies have reduced severe malaria cases and deaths in endemic regions of Africa, Asia and the Americas, specifically: (1) artemisinin-based combination therapy (ACT); (2) insecticide-treated bed nets (ITNs); and, (3) intermittent preventive treatment with sulfadoxine-pyrimethamine in pregnancy (IPTp). The rationale for this study was to examine communities in Dangassa, Mali where, in 2015, two additional control strategies were implemented: ITN universal coverage and seasonal malaria chemoprevention (SMC) among children under 5 years old. Methods This was a prospective study based on a rolling longitudinal cohort of 1401 subjects participating in bi-annual smear surveys for the prevalence of asymptomatic Plasmodium falciparum infection and continuous surveillance for the incidence of human disease (uncomplicated malaria), performed in the years from 2012 to 2020. Entomological collections were performed to examine the intensity of transmission based on pyrethroid spray catches, human landing catches and enzyme-linked immunosorbent assay (ELISA) testing for circumsporozoite antigen. Results A total of 1401 participants of all ages were enrolled in the study in 2012 after random sampling of households from the community census list. Prevalence of infection was extremely high in Dangassa, varying from 9.5 to 62.8% at the start of the rainy season and from 15.1 to 66.7% at the end of the rainy season. Likewise, the number of vectors per house, biting rates, sporozoites rates, and entomological inoculation rates (EIRs) were substantially greater in Dangassa. Discussion The findings for this study are consistent with the progressive implementation of effective malaria control strategies in Dangassa. At baseline (2012–2014), prevalence of P. falciparum was above 60% followed by a significant year-to-year decease starting in 2015. Incidence of uncomplicated infection was greater among children < 5 years old, while asymptomatic infection was more frequent among the 5–14 years old. A significant decrease in EIR was also observed from 2015 to 2020. Likewise, vector density, sporozoite rates, and EIRs decreased substantially during the study period. Conclusion Efficient implementation of two main malaria prevention strategies in Dangassa substantially contribute to a reduction of both asymptomatic and symptomatic malaria from 2015 to 2020.

Estimated distribution of malaria cases among children in sub-Saharan Africa by specified age categories using data from the Global Burden of Diseases 2019

“…Furthermore, a four quarterly survey of 7,000 children less than 10 years old in Ethiopia found that the incidence rate varied between 2.4 and 20% in high-altitude areas, depending on the quarter of the year [ 12 ]. A study conducted in Mali among 1401 participants (over 65% less than 20 years) from 2012 to 2020, reported significantly different estimates at the start and end of the rainy season, demonstrating the impact of seasonality/transmission intensity on malaria distribution [ 13 ]. The disparity in published estimates can be attributed to differences in patient inclusion, malaria case definition, assumptions made in the estimation, differences in seasonality, and transmission intensity [ 2 ].…”

A Decade of Progress Accelerating Malaria Control in Mali: Evidence from the West Africa International Center of Excellence for Malaria Research

“…In Dangassa, the prevalence of asymptomatic infection decreased from 60.3% in 2012 to just 18.5% in 2020. 25 In Dioro, prevalence rates abruptly increased from 32.8% in 2012 to 61.6% in 2014 (following the discontinuation of universal healthcare access supported by the MVP). In Koulikoro, the newest WA-ICEMR site established in 2018, the prevalence of asymptomatic infection declined from 11.5% in 2018 to 7.3% in 2020.…”

Malaria among the elderly in five communities of Osun East district, Southwest Nigeria: Prevalence and association with non-communicable diseases

“… 14 – 16 However, there is also a possibility that old age and the presence of non-communicable diseases (NCDs) lead to the attenuation of this immunity. 17 , 18 These may put elderly persons at a significantly higher risk of malaria and its unacceptable sequelae. 15 , 19 , 20 …”

“…[14][15][16] However, there is also a possibility that old age and the presence of non-communicable diseases (NCDs) lead to the attenuation of this immunity. 17,18 These may put elderly persons at a significantly higher risk of malaria and its unacceptable sequelae. 15,19,20 Moreover, the burden of NCDs is increasing among older adults in many economically developing countries, including Nigeria.…”