Implications of insecticide resistance for malaria vector control with long-lasting insecticidal nets: evidence from health facility data from Benin.

BACKGROUND: Insecticide-based interventions have averted more than 500 million malaria cases since 2000, but insecticide resistance in mosquitoes could bring about a rebound in disease and mortality. This study investigated whether insecticide resistance was associated with increased incidence of clinical malaria. METHODS: In an area of southern Benin with insecticide resistance and high use of insecticide-treated nets (ITNs), malaria morbidity and insecticide resistance were measured simultaneously in 30 clusters (villages or collections of villages) multiple times over the course of 2 years. Insecticide resistance frequencies were measured using the standard World Health Organization bioassay test. Malaria morbidity was measured by cases recorded at health facilities both in the whole population using routinely collected data and in a passively followed cohort of children under 5 years old. RESULTS: There was no evidence that incidence of malaria from routinely collected data was higher in clusters with resistance frequencies above the median, either in children aged under 5 (RR = 1.27 (95% CI 0.81-2.00) p = 0.276) or in individuals aged 5 or over (RR = 1.74 (95% CI 0.91-3.34) p = 0.093). There was also no evidence that incidence was higher in clusters with resistance frequencies above the median in the passively followed cohort (RR = 1.11 (0.52-2.35) p = 0.777). CONCLUSIONS: This study found no association between frequency of resistance and incidence of clinical malaria in an area where ITNs are the principal form of vector control. This may be because, as other studies have shown, ITNs continue to offer some protection from malaria even in the presence of insecticide resistance. Irrespective of resistance, nets provide only partial protection so the development of improved or supplementary vector control tools is required to reduce Africa's unacceptably high malaria burden.

Impact of long-lasting, insecticidal nets on anaemia and prevalence of Plasmodium falciparum among children under five years in areas with highly resistant malaria vectors.

BACKGROUND: The widespread use of insecticide-treated nets (LLINs) leads to the development of vector resistance to insecticide. This resistance can reduce the effectiveness of LLIN-based interventions and perhaps reverse progress in reducing malaria morbidity. To prevent such difficulty, it is important to know the real impact of resistance in the effectiveness of mosquito nets. Therefore, an assessment of LLIN efficacy was conducted in malaria prevention among children in high and low resistance areas. METHODS: The study was conducted in four rural districts and included 32 villages categorized as low or high resistance areas in Plateau Department, south-western Benin. Larvae collection was conducted to measure vector susceptibility to deltamethrin and knockdown resistance (kdr) frequency. In each resistance area, around 500 children were selected to measure the prevalence of malaria infection as well as the prevalence of anaemia associated with the use of LLINs. RESULTS: Observed mortalities of Anopheles gambiae s.s population exposed to deltamethrin ranged from 19 to 96%. Knockdown resistance frequency was between 38 and 84%. The prevalence of malaria infection in children under five years was 22.4% (19.9-25.1). This prevalence was 17.3% (14.2-20.9) in areas of high resistance and 27.1% (23.5-31.1) in areas of low resistance (p=0.04). Eight on ten children that were aged six - 30 months against seven on ten of those aged 31-59 months were anaemic. The anaemia observed in the six to 30-month old children was significantly higher than in the 31-59 month old children (p=0.00) but no difference associated with resistance areas was observed (p=0.35). The net use rate was 71%. The risk of having malaria was significantly reduced (p<0.05) with LLIN use in both low and high resistance areas. The preventive effect of LLINs in high resistance areas was 60% (95% CI: 40-70), and was significantly higher than that observed in low resistance areas (p<0.05). CONCLUSION: The results of this study showed that the resistance of malaria vectors seems to date not have affected the impact of LLINs and the use of LLINs was highly associated with reduced malaria prevalence irrespective of resistance.

Situation analysis of urogenital bilharzia in West Africa (2010-2021) and control strategies and prospects: systematic review and meta-analysis.

Schistosomes are parasitic diseases caused by flatworms (schistosomes or bilharzia), transmitted in the urine or in the faeces, and involving intermediate hosts (freshwater molluscs). Their recrudescence in endemic areas is no longer in question and remains a crucial public health problem in the world in general and in West Africa in particular. In order to eradicate bilharzia, many control strategies and policies have been implemented on both sides. The objective of this systematic literature review is to synthesize the existing evidence on control strategies implemented by West African countries. To achieve this, data were collected from PubMed, Direct Science, Web of Sciences, Google Scholar, PloS and Banque de Données de Santé Publique (BDSP), using appropriate keywords. Academic articles and theses written in French or English that evaluated the analysis of a bilharzia situation in West Africa were selected. Sixteen scientific papers were selected for the study, ten of which were used for a meta-analysis. The systematic review revealed that bilharzia is still an endemic disease in West Africa. Clearly, it continues to wreak havoc on the population, especially among school children. Rural areas are the most affected by the disease. Strategies to control bilharzia are based on preventive and curative treatment of the infection with chemotherapy and vector control of soil molluscs (host and vector of bilharzia eggs). Praziquantel is the main known antibilharzian. Also, the species most frequently found in analyses are S. haematobiumand S. mansonii. This review has allowed to evaluate the control strategies carried out and to deduce the strengths and weaknesses, in order to define the perspectives for the efficiency of the anti-bilharzia control for the eradication of bilharzia in the endemic zones of West Africa.

Is exclusive breastfeeding an option or a necessity in Africa? A pooled study using the deuterium oxide dose-to-mother technique.

Given the valuable health, development, and economic benefits of human milk Exclusive Breastfeeding (EBF) is recommended by the World Health Organisation for the first six months of an infant's life. Many resource-limited regions in Africa do not line-up with these recommendations, therefore EBF promotion efforts on the continent need to be scaled up and monitored. This study explores the human milk intake volumes of 5 countries (Benin, Central African Republic, Morocco, South Africa and Tanzania) both at country level and in a pooled sample of children at 3 months (n= 355) and at 6 months (n=193). Mean human milk intake volumes in the pooled samples were 697.6 g/day at 3 months and 714.9 g/day at 6 months. EBF was determined both by maternal recall as well as using the deuterium oxide dose-to-mother technique, using two different cut-offs of non-milk oral intake. Comparison of these results showed substantial over-reporting of EBF by maternal recall, which suggests that actual rates of EBF are even lower than reported, thus highlighting the importance of scaling-up EBF promotion strategies.