Centre National de Recherche et de Formation sur le Paludisme

Malaria vector control tools currently focus on insecticide treated nets (ITNs) and indoor residual spraying in malaria-endemic locations, but additional preventative strategies are needed to address protection gaps. Larval source management (LSM) includes larvicide application to aquatic habitat and an array of alternative forms of environmental efforts. An individual-based transmission model for falciparum malaria is used to demonstrate the theoretical benefit of suppressing malaria adult mosquito vector densities through LSM. The model simulates results of epidemiological trials from Western Kenya (a hilly area with papyrus swamps adjacent to human settlements and moderate to high perennial malaria transmission) and Côte d'Ivoire (an area with Sudanese climate, reducing vegetation cover and high transmission) that applied larvicide alongside ITNs, and investigates whether estimated changes in adult density can be used to project changes in human malaria. In the Western Kenya setting generalised linear models estimate 82% (90% credible intervals: 64% - 92%) and 88% (79% - 94%) reductions in the proportion of adult Anopheles funestus and Anopheles gambiae complex mosquitoes respectively as measured by CDC light traps. In Côte d'Ivoire, an 82% (56% - 93%) reduction of the dominant An. gambiae vector was estimated using standard window trap and pyrethrum spray catch. Both studies had variable village-level impacts. The transmission dynamics model predicted that these entomological impacts would result in a reduction in malaria prevalence in children of 6-months to 10-years of age of 48 - 72% in Kenya, and a 11 - 78% reduction in all-age clinical incidence across villages in Côte d'Ivoire, which are broadly consistent with the empirically observed outcomes. High heterogeneity between villages within the same study indicate that the relative or absolute reductions in mosquito adult density observed in these trials cannot be simply extrapolated to other regions. The LSM strategy adopted, unit area covered, and multiple environmental covariates all contribute to differences in indicators that could be used to assess entomological impacts and the corresponding epidemiological outcomes. This important malaria control tool was impactful across all sites examined, though further work is needed to understand how best to use this tool in the fight against malaria.

Malaria vector control tools currently focus on insecticide treated nets (ITNs) and indoor residual spraying in malaria-endemic locations, but additional preventative strategies are needed to address protection gaps. Larval source management (LSM) includes larvicide application to aquatic habitat and an array of alternative forms of environmental efforts. An individual-based transmission model for falciparum malaria is used to demonstrate the theoretical benefit of suppressing malaria adult mosquito vector densities through LSM. The model simulates results of epidemiological trials from Western Kenya (a hilly area with papyrus swamps adjacent to human settlements and moderate to high perennial malaria transmission) and Côte d’Ivoire (an area with Sudanese climate, reducing vegetation cover and high transmission) that applied larvicide alongside ITNs, and investigates whether estimated changes in adult density can be used to project changes in human malaria. In the Western Kenya setting generalised linear models estimate 82% (90% credible intervals: 64% – 92%) and 88% (79% – 94%) reductions in the proportion of adult Anopheles funestus and Anopheles gambiae complex mosquitoes respectively as measured by CDC light traps. In Côte d’Ivoire, an 82% (56% – 93%) reduction of the dominant An. gambiae vector was estimated using standard window trap and pyrethrum spray catch. Both studies had variable village-level impacts. The transmission dynamics model predicted that these entomological impacts would result in a reduction in malaria prevalence in children of 6-months to 10-years of age of 48 – 72% in Kenya, and a 11 – 78% reduction in all-age clinical incidence across villages in Côte d’Ivoire, which are broadly consistent with the empirically observed outcomes. High heterogeneity between villages within the same study indicate that the relative or absolute reductions in mosquito adult density observed in these trials cannot be simply extrapolated to other regions. The LSM strategy adopted, unit area covered, and multiple environmental covariates all contribute to differences in indicators that could be used to assess entomological impacts and the corresponding epidemiological outcomes. This important malaria control tool was impactful across all sites examined, though further work is needed to understand how best to use this tool in the fight against malaria.

Abstract IntroductionMalaria is a public health threat in Mali, with high morbidity (37%) and mortality (25%) rates. Malaria risk stratification is needed to identify different transmission zones and prioritize the interventions, especially in resource-limited contexts. For the new National Strategic Plan, we updated stratification with World Health Organization (WHO) recommendation. This study presents the selection of interventions based on stratification.MethodData collection covered all the 75 Health Districts (HDs) in the country for the period 2018-2022. This was further supplemented by national survey data on parasitology and entomology in Mali. To estimate the adjusted incidence, the analysis considered health data reporting, malaria diagnostic positivity and health facility attendance rates at health district level to malaria cases estimated. Mixed interventions were defined based on adjusted incidence, prevalence, seasonality, vector resistance to insecticides and parasite distribution by Health Districts or region according to data available.ResultsFour strata have been defined according to the 2017 WHO Malaria Elimination Framework. Most HDs (54) fall within the highest and moderate transmission areas, covering 84% of the population (about 18 million) located in the southern and central regions. A total of 19 intervention packages were selected and adapted. We identified 61 out of 75 eligible HDs for the LLINs mass distribution campaign, 57 HDs for SMC, 67 for IPTp including community IPTp and 19 HD for vaccination.ConclusionA half of Malian population live in high-risk areas. These districts require a continuous intensification of interventions. Malaria stratification was critical for strategic planning and appropriate deployment of malaria control interventions in Mali.

BackgroundInsecticide-treated nets (ITNs) are the most commonly deployed tools for controlling malaria transmission in sub-Saharan Africa. However, some reports associate multiple alternative uses of nets with poor disposal practices, prompting this study to assess existing alternative uses and disposal practices of old ITNs in Burkina Faso after four universal distribution campaigns.MethodsA quantitative survey combined with qualitative data collection was used to describe existing alternative uses and disposal practices for old ITNs in households from selected study sites in the three climatic zones of Burkina Faso. A survey questionnaire was distributed to 3,780 participants, and 12 focus groups were held to elucidate responses regarding existing disposal practices and alternative uses of ITNs.ResultsOf the 3780 households surveyed, 87.4% (3,330) reported having disposed of their ITNs when they were no longer usable due to age or wear. The most commonly cited disposal methods included alternative uses (67.4%), disposal with other garbage (61.4%), and burying (9%). In addition, the most common alternative uses included fencing for crops and seedlings (51.8%); ropes for tying items (40.4%); animal protection fencing (17.8%); house fencing (16.8%); bed covers (13.3%) and curtains for doors or windows (12.6%). Furthermore, trends in ITNs disposal mechanisms and alternative uses differed between study sites in each climate zone. All these ITNs disposal mechanisms and the different types of alternative use of old ITNs were confirmed in the focus group discussions.ConclusionThe findings underscore the need for comprehensive strategies to manage the disposal and repurposing of old ITNs in Burkina Faso. Addressing gaps in disposal guidelines, promoting safe and beneficial reuse practices, and actively involving communities in the decision-making process can help mitigate health risks associated with the improper disposal and repurposing of old insecticide-treated nets and improve the overall effectiveness of malaria control programmes. Through these efforts, both public health and environmental concerns can be addressed in a sustainable and collaborative manner.

SummaryBackgroundInsecticide treated nets (ITNs) are the most important malaria prevention tool in Africa but the rise of pyrethroid resistance in mosquitoes is likely impeding control. WHO has recommended a novel pyrethroid–pyrrole ITN following evidence of epidemiological benefit in two cluster-randomised, controlled trials (CRTs). It remains unclear how effective more costly pyrethroid–pyrrole ITNs are compared with other tools, or whether they should be deployed when budgets are limited. We aimed to compare the epidemiological impact and cost-effectiveness of the mass distribution of pyrethroid–pyrrole ITNs relative to other ITNs over 3 years in different African settings.MethodsIn this individual-based malaria transmission dynamics modelling study we characterise the entomological impact of ITNs using data from a systematic review of experimental hut trials from across Africa. This African entomological data was used to inform an individual-based malaria transmission dynamics model, which was validated against CRT results from Benin and Tanzania. The full impact of new ITNs was quantified for trial sites and simulation was used to project impact in different settings which were included within an accessible interface (the Malaria Intervention Tool) to support National Malaria Programmes to explore how vector control tools and budgets could be allocated across regions to avert the most cases.FindingsThe model projects that distributing pyrethroid–pyrrole ITNs averted 65% (95% credible interval 48–74) of cases over 3 years in Tanzania, and 75% (28–93) in Benin. The model indicates that trials might have underestimated the benefits of switching ITNs by 12–16% over 3 years because participants stopped using trial-allocated nets. In moderate endemicity non-trial settings, pyrethroid–pyrrole ITNs are projected to reduce malaria prevalence by 25–60% and switching from pyrethroid-only ITNs is probably highly cost-effective in most locations given current prices, averting an additional 10–30% of cases.InterpretationThe benefit of pyrethroid–pyrrole ITNs varies by setting but is generally the most cost-effective indoor vector control intervention in Africa. National Malaria Programmes can strategise deployment to maximise impact. Entomological data could broadly predict epidemiological impact, although there are some inconsistencies, illustrating the challenge in capturing the dynamics across diverse settings.FundingUnitaid, Bill & Melinda Gates Foundation, the UK Medical Research Council, Wellcome Trust, and the UK Foreign, Commonwealth & Development Office.

Abstract Long-lasting insecticidal nets and indoor residual sprays have played a major role in significantly reducing the burden of malaria. However, the management of mosquitoes resistant to current insecticides continues to be challenging. A promising new strategy is drug-based vector control where drugs are administered to vector hosts rendering the host blood toxic to mosquitoes ¾ thereby reducing mosquito lifespan, fecundity and onward transmission of pathogens. Afoxolaner, fluralaner and lotilaner are isoxazoline derivatives widely used as systemic insecticides for ectoparasite control in companion animals. Here, the mosquitocidal activity of these compounds against Anopheles gambiae s.s, Anopheles coluzzii, Aedes aegypti and Anopheles funestus mosquitoes was evaluated. The effect of antibiotic treatment and different carbohydrates in artificial nectar meals on isoxazoline activity was also investigated. All isoxazolines tested showed rapid killing with little difference in susceptibility between different species and genera of mosquitoes. Fluralaner showed the most potent mosquitocidal effects with IC50 values ranging from 44 to 87 nM when mortality was assessed at 24h post-feeding. Addition of the antibiotic cocktail or variations in sugar diet did not affect isoxazoline potency. In conclusion, data indicate potent and rapid mosquitocidal effects of isoxazolines that are likely unaffected by mosquito sugar feeding behaviour and microbiome dynamics.

Korsimoro, located in the Sudano-Sahelian region of north-central Burkina Faso, is heavily dependent on agriculture, making it particularly vulnerable to climate change. This study examines the interaction between biophysical factors and agricultural practices in Korsimoro. Using a multidisciplinary approach, we carried out a geospatial analysis using t maps from various sources (BUNASOLS, IGB). A detailed soil evaluation was carried out to assess the agronomic potential of the different soil types. Historical rainfall data was analyzed to understand the climatic variability of the region. The results reveal that the leached tropical ferruginous indurated soils (FLIPP), which occupy almost half of Korsimoro, have low agronomic potential due to their shallow depth and limited water retention capacity. These soil characteristics, combined with the decline in vegetation cover due to deforestation and overgrazing, make the region highly vulnerable to soil degradation. In addition, the region experiences high variability in rainfall, which poses a major threat to agricultural productivity. As a result, the low agronomic potential of the soil and the increasing variability of the climate have a direct impact on farming practices in Korsimoro. Farmers in the region are facing difficulties in maintaining crop yields and ensuring food security. To improve the resilience of farming systems in Korsimoro, we recommend the following: Site-specific soil management practices: Given the heterogeneity of soil types, adapted soil management practices, such as conservation tillage and organic fertilization, should be encouraged to improve soil fertility and water retention. Improved water management: Investments in water harvesting, irrigation and water efficiency technologies are essential to mitigate the effects of drought and ensure a stable water supply for agriculture. Agroforestry: Integrating trees into farming systems can help to improve soil structure, reduce erosion and enhance biodiversity. Climate-smart farming: Adopting climate-smart farming practices, such as drought-resistant crop varieties, can help farmers adapt to changing climatic conditions. Capacity building: Providing farmers with training and extension services on sustainable farming practices is essential to ensure the long-term success of these interventions. By implementing these recommendations, Korsimoro can improve agricultural productivity, enhance food security and contribute to more sustainable land management practices.

BackgroundIndoor residual spraying (IRS) is a cornerstone malaria control intervention in Burkina Faso. From 2018 to 2021, non-pyrethroid IRS was implemented annually in two regions of Burkina Faso with distinct malaria transmission patterns, concurrently with annual seasonal malaria chemoprevention (SMC), and a mass insecticide-treated net (ITN) distribution in 2019.MethodsA retrospective quasi-experimental approach was used to evaluate the impact of the 2018, 2020, and 2021 IRS campaigns on routinely reported confirmed malaria case incidence at health facilities. The 2019 campaign was excluded due to lack of data reporting during a health sector strike. Controlled interrupted time series models were fit to detect changes in level and trend in malaria case incidence rates following each IRS campaign when compared to the baseline period 24-months before IRS. IRS districts Solenzo (Sudano-Sahelien climate), and Kampti (tropical climate) were compared with neighbouring control districts and the analyses were stratified by region. Modelled health facility catchment population estimates based on travel time to health facilities and weighted by non-malaria outpatient visits were used as an offset. The study period encompassed July 2016 through June 2022, excluding July 2018 to June 2019.ResultsDistrict-level population and structure coverage achieved by IRS campaigns was greater than 85% in 2018, 2020, and 2021 in Solenzo and Kampti. In Solenzo a significant difference in malaria case incidence rates was detected after the 2018 campaign (IRR = 0.683; 95% CI 0.564–0.827) when compared to the control district. The effect was not detected following the 2020 or 2021 IRS campaigns. In Kampti, estimated malaria incidence rates were between 36 and 38% lower than in the control district following all three IRS campaigns compared to the baseline period.ConclusionsImplementation of IRS in Kampti, a tropical region of Burkina Faso, appeared to have a consistent significant beneficial impact on malaria case rates. An initial positive impact in Solenzo after the first IRS campaign was not sustained in the successive evaluated IRS campaigns. This study points to a differential effect of IRS in different malaria transmission settings and in combination with ITN and SMC implementation.

The majority of Plasmodium spp infections in endemic countries are asymptomatic and a source of onward transmission to mosquitoes. We aimed to examine whether Plasmodium falciparum transmission and malaria burden could be reduced by improving early detection and treatment of infections with active screening approaches. In this 18-month cluster randomised study in Sapone, Burkina Faso, households were enrolled and randomly assigned (1:1:1) to one of three groups: group 1 (control) received standard of care only, group 2 received active weekly, at home, fever screening by a community health worker regardless of symptoms, participants with a fever received a rapid diagnostic test (RDT) and treatment if RDT positive, and group 3 received active weekly fever screening (as in group 2) plus a monthly RDT regardless of symptoms, and treatment if RDT positive. Eligible households had a minimum of threeeligible residents, one in each age group (<5years, 5-15years, and >15years). The primary outcome was parasite prevalence by quantitative PCR (qPCR) in the end-of-study cross-sectional survey. Secondary outcomes included parasite and gametocyte prevalence and density in all three end-of-season cross-sectional surveys, incidence of infection, and the transmissibility of infections to mosquitoes. This trial was registered at ClinicalTrials.gov (NCT03705624) and is completed. A total of 906individuals from 181households were enrolled during two phases, and participated in the study. 412individuals were enrolled between Aug 9and 17, 2018, and participated in phase 1and 494individuals were enrolled between Jan 10and 31, 2019, in phase 2. In the end-of-study cross-sectional survey (conducted between Jan13and21,2020), Pfalciparum prevalence by qPCR was significantly lower in group 3 (29·26%; 79of 270), but not in group 2 (45·66%; 121of 265), when compared with group 1 (48·72%; 133of 273; risk ratio 0·65 [95% CI 0·52-0·81]; p=0·0001). Total parasite and gametocyte prevalence and density were also significantly lower in group3in all surveys. The largest differences were seen at the end of the dry season, with gametocyte prevalence 78·4% and predicted transmission potential 98·2% lower in group 3than in group1. Active monthly RDT testing and treatment can reduce parasite carriage and the infectious reservoir of Pfalciparum to less than 2% when used during the dry season. This insight might inform approaches for malaria control and elimination. Bill & Melinda Gates Foundation, European Research Council, and The Netherlands Organization for ScientificResearch.

Sclerocarya birrea (A. Rich). Hochst, popularly known as Morula, is a plant in the Anacardiaceae family. The bark, fruits, and leaves have traditionally been used to manage a variety of health conditions, most especially diabetes. Unfortunately, there is a scarcity of data and publications on the toxicity and safety of this plant. The current study was designed to assess the acute and chronic toxicity of a hydro-ethanolic extract of Sclerocarya birrea in albino rats. Sclerocarya birrea was extracted using an 80-20% hydro-ethanolic solution. For the acute toxicity study, female Wistar albino rats were treated with hydro-ethanolic leaf extract at a dose of 5000 mg/kg body weight and followed-up for 14 days. In the chronic toxicity study, 40 healthy Wistar albino rats were divided in 4 groups. The three treatment groups were administered the leaf hydro-ethanolic extract orally at dosages of 30, 150, and 1000 mg/kg once day for 90 days and the fourth group was a control group. Body and organs weights, haematological, serum biochemical, and histopathological parameters were measured at the end of the experiment. Single-dose oral administration of hydro-ethanolic leaf extract of Sclerocarya birrea at 5000 mg/kg produced no mortality indicating the LD50 is greater than 5000 mg/kg body weight. Following 90 days of administration of a hydro-ethanolic extract of Sclerocarya birrea leaves, there was no significant change in body and organs weights. Furthermore, biochemical, haematological and histopathological parameters did not vary significantly. This data indicates neither acute or chronic toxicity in rats and is consistent with the widespread and long-term usage of Sclerocarya birrea in African traditional medicine.