6 research outputs found
Insecticide resistance status in Anopheles gambiae in southern Benin.
No full textBACKGROUND: The emergence of pyrethroid resistance in Anopheles gambiae has become a serious concern to the future success of malaria control. In Benin, the National Malaria Control Programme has recently planned to scaling up long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) for malaria prevention. It is, therefore, crucial to monitor the level and type of insecticide resistance in An. gambiae, particularly in southern Benin where reduced efficacy of insecticide-treated nets (ITNs) and IRS has previously been reported. METHODS: The protocol was based on mosquito collection during both dry and rainy seasons across forty districts selected in southern Benin. Bioassay were performed on adults collected from the field to assess the susceptibility of malaria vectors to insecticide-impregnated papers (permethrin 0.75%, delthamethrin 0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. The species within An. gambiae complex, molecular form and presence of kdr and ace-1 mutations were determined by PCR. RESULTS: Strong resistance to permethrin and DDT was found in An. gambiae populations from southern Benin, except in Aglangandan where mosquitoes were fully susceptible (mortality 100%) to all insecticides tested. PCR showed the presence of two sub-species of An. gambiae, namely An. gambiae s.s, and Anopheles melas, with a predominance for An. gambiae s.s (98%). The molecular M form of An. gambiae was predominant in southern Benin (97%). The kdr mutation was detected in all districts at various frequency (1% to 95%) whereas the Ace-1 mutation was found at a very low frequency (<or= 5%). CONCLUSION: This study showed a widespread resistance to permethrin in An. gambiae populations from southern Benin, with a significant increase of kdr frequency compared to what was observed previously in Benin. The low frequency of Ace-1 recorded in all populations is encouraging for the use of bendiocarb as an alternative insecticide to pyrethroids for IRS in Benin
Contribution of poses screen preimpregnated (PSP) installed at openings and eaves of dwellings in the reduction of malaria transmission in the commune of aguégués in bénin
No full textAbstractObjectiveTo evaluate the contribution of poses screen pre-impregnated (PSP) installed at openings and eaves of dwellings in the reduction of malaria transmission in the commune of Aguégués in Bénin.MethodsThe PSP were manufactured from preimpregnated Olyset Net. They were installed at windows, eaves and doors of 70 dwellings. 320 children aged 6-59 months were treated and 311 children were recruited in the control zone. Variables measured are: plasmodic index (IP), gametocyte index, parasite density (PD), fever, hemoglobin, anemia.ResultsThe global IP was 16.62% with PSP and 72.20% without PSP. Gametocyte index did not differ significantly between the treated zone (27.8) and the control zone (29.1). The total geometric mean of DP was 309 in the treated zone and 600 in the control zone. Hemoglobin level is 8.7 in the control zone and 9.5 in the treated zone. We noted a predominance of anemia in the control zone compared to the treated zone.ConclusionsThe PSP have contributed to a significant reduction in morbidity in the commune of Aguégués
Average Household Size and the Eradication of Malaria
No full textEfforts to eradicate malaria during the 20th century succeeded in some parts of the world but failed in others. Malaria also disappeared spontaneously in several countries for reasons that remain an enigma. The connection between malaria and poverty has long been noted. Here we focus on a specific aspect: household size, which has hitherto received little attention. We find strong evidence that when average household size drops below four persons, the probability of malaria eradication jumps dramatically and its incidence in the population drops significantly. This effect is independent of all commonly-studied explanatory variables and was globally valid across all climate zones irrespective of counter measures, vector species, or Plasmodium species. We propose an explanation based on the dispersal mechanism of the parasite. Malaria is transmitted at night by mosquito bite. The mosquito typically spreads the Plasmodium only locally over short distances to new human victims. To survive, the Plasmodium depends on infected humans making social contacts over longer distances. When household size decreases sufficiently, these contacts cross a threshold value that changes the balance between extinctions and replacements and the Plasmodium disappears on its own. We test this interpretation by contrasting our malaria model with dengue fever, which is also poverty-related and mosquito-borne but transmitted differently, namely through daytime exposure. Household size is uncorrelated with dengue incidence, whereas an indicator of outdoor work that is insignificant in the malaria model is highly significant for dengue. We conclude that poverty-induced malaria infection risks are likely to persist, but a focus on reducing effective household size can be a feasible and promising means of its eradication.Malaria;dengue fever, household size, DDT
Attrition, physical integrity and insecticidal activity of long-lasting insecticidal nets in sub-Saharan Africa and modelling of their impact on vectorial capacity
No full textLong-lasting insecticidal nets (LLINs) are the primary malaria prevention and control intervention in many parts of sub-Saharan Africa. While LLINs are expected to last at least 3 years under normal use conditions, they can lose effectiveness because they fall out of use, are discarded, repurposed, physically damaged, or lose insecticidal activity. The contributions of these different interrelated factors to durability of nets and their protection against malaria have been unclear.; Starting in 2009, LLIN durability studies were conducted in seven countries in Africa over 5 years. WHO-recommended measures of attrition, LLIN use, insecticidal activity, and physical integrity were recorded for eight different net brands. These data were combined with analyses of experimental hut data on feeding inhibition and killing effects of LLINs on both susceptible and pyrethroid resistant malaria vectors to estimate the protection against malaria transmission-in terms of vectorial capacity (VC)-provided by each net cohort over time. Impact on VC was then compared in hypothetical scenarios where one durability outcome measure was set at the best possible level while keeping the others at the observed levels.; There was more variability in decay of protection over time by country than by net brand for three measures of durability (ratios of variance components 4.6, 4.4, and 1.8 times for LLIN survival, use, and integrity, respectively). In some countries, LLIN attrition was slow, but use declined rapidly. Non-use of LLINs generally had more effect on LLIN impact on VC than did attrition, hole formation, or insecticide loss.; There is much more variation in LLIN durability among countries than among net brands. Low levels of use may have a larger impact on effectiveness than does variation in attrition or LLIN degradation. The estimated entomological effects of chemical decay are relatively small, with physical decay probably more important as a driver of attrition and non-use than as a direct cause of loss of effect. Efforts to maximize LLIN impact in operational settings should focus on increasing LLIN usage, including through improvements in LLIN physical integrity. Further research is needed to understand household decisions related to LLIN use, including the influence of net durability and the presence of other nets in the household
The evolving SARS-CoV-2 epidemic in Africa: insights from rapidly expanding genomic surveillance
No full textInvestment in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing in Africa over the past year has led to a major increase in the number of sequences that have been generated and used to track the pandemic on the continent, a number that now exceeds 100,000 genomes. Our results show an increase in the number of African countries that are able to sequence domestically and highlight that local sequencing enables faster turnaround times and more-regular routine surveillance. Despite limitations of low testing proportions, findings from this genomic surveillance study underscore the heterogeneous nature of the pandemic and illuminate the distinct dispersal dynamics of variants of concern—particularly Alpha, Beta, Delta, and Omicron—on the continent. Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve while the continent faces many emerging and reemerging infectious disease threats. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century
The evolving SARS-CoV-2 epidemic in Africa: insights from rapidly expanding genomic surveillance
No full textInvestment in SARS-CoV-2 sequencing in Africa over the past year has led to a major increase in the number of sequences generated, now exceeding 100,000 genomes, used to track the pandemic on the continent. Our results show an increase in the number of African countries able to sequence domestically, and highlight that local sequencing enables faster turnaround time and more regular routine surveillance. Despite limitations of low testing proportions, findings from this genomic surveillance study underscore the heterogeneous nature of the pandemic and shed light on the distinct dispersal dynamics of Variants of Concern, particularly Alpha, Beta, Delta, and Omicron, on the continent. Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve, while the continent faces many emerging and re-emerging infectious disease threats. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century
