Long-lasting Insecticide-treated Nets Research Articles

Genetic differentiation and bottleneck effects in the malaria vectors Anopheles farauti and Anopheles punctulatus after an LLIN-based vector control program in Papua New Guinea.

Implementation of long-lasting insecticide-treated net (LLIN) programs to control human malaria transmission leads to substantial reductions in the abundance of Anopheles mosquitoes, but the impact on the population genetic structure of the malaria vectors is poorly known, nor has it been investigated in Papua New Guinea, where malaria is highly endemic and where several species of Anopheles have vector roles. Here, we applied Wright's F-statistic, analysis of molecular variance, Bayesian structure analysis, and discriminant analysis of principle components to microsatellite genotype data to analyze the population genetic structure of Anopheles farauti between and within the northern and southern lowland plains and of Anopheles punctulatus within the northern plain of Papua New Guinea after such a program. Bottleneck effects in the two malaria vectors were analyzed using Luikart and Cornuet's tests of heterozygosity. A large, panmictic population of An. punctulatus pre-LLIN program diverged into two subregional populations corresponding to Madang and East Sepik provinces post-LLIN distribution and experienced a genetic bottleneck during this process. By contrast, the An. farauti population existed as two regional populations isolated by mountain ranges pre-LLIN, a genetic structure that persisted after the distribution of LLINs with no further geographic differentiation nor evidence of a genetic bottleneck. These findings show the differential response of populations of different vector species to interventions, which has implications for program sustainability and gene flow.

Malaria Prevalence and Macroeconomic Output in Ghana, 1990 to 2019.

In Ghana, malaria remains the number 1 reason for outpatient department visits, making it a major public health problem. Thus, there could be significant lost productivity days as a result of malaria morbidity and mortality, which could negatively affect economic output at the macrolevel. Nonetheless, there is a dearth of empirical evidence of the effect of malaria on macroeconomic output in Ghana. This study therefore aims to provide the foremost empirical evidence regarding the effect of malaria prevalence on macroeconomic output in Ghana using a time series design with data spanning the period 1990 to 2019. Gross Domestic Product (GDP), serving as a proxy for macroeconomic output, is the dependent variable, while the prevalence of malaria (overall, among only males and among only females) serves as the main independent variable. The Ordinary Least Square (OLS) regression is used as the baseline estimation technique and the Instrumental Variable Two-Stage Least Square (IV2SLS) regression is employed as the robustness check estimator due to its ability to deal with endogeneity. The IV2SLS regression results show that a percentage increase in the overall prevalence of malaria is associated with a 1.16% decrease in macroeconomic output at 1% significance level. We also find that the effect of malaria in males on macroeconomic output is slightly higher relative to females. The findings from the OLS regression are not qualitatively different from the IV2SLS regression estimates. There is therefore the need to strengthen efforts such as quality case management, larval source management, mass distribution of long-lasting insecticide-treated bed nets, social behavior change, surveillance (both epidemiological and entomological), intermittent preventive treatment of malaria in pregnancy, research among others, which are important toward eliminating malaria.

Knowledge and practices of private pharmacy auxiliaries on malaria in Abidjan, Côte d’Ivoire

BackgroundThe emergence of resistance to artemisinin derivatives in Southeast Asia constitutes a serious threat for other malaria endemic areas, particularly in Côte d’Ivoire. To delay this resistance, the application of the control measures recommended by the National Malaria Control Programme (NMCP) for a correct management, in the private pharmacies, is a necessity. The purpose of this study was, therefore, to assess the level of knowledge and practices of private pharmacy auxiliary in Abidjan about the management of malaria.MethodsA descriptive cross-sectional study was conducted from April to November 2015. It included auxiliaries of private pharmacies in Abidjan. Data collection material was a structured an open pretested questionnaire. Data analysis was carried out using Package for Social Science (SPSS) software version 21.1. Chi square test was used to compare proportions for a significance threshold of 0.05 for the p value.ResultsA total, 447 auxiliaries from 163 private pharmacies were interviewed. It was noted that the auxiliaries had a good knowledge of clinical signs of uncomplicated malaria (99.1%), biological examinations (54.6% for the thick film and 40.7% for rapid diagnostic tests (RDTs) and anti-malarial drugs (99.3% for artemether + lumefantrine, AL). The strategies of vector control (long-lasting insecticide-treated mosquito nets (LLITNs, Repellent ointments, cleaning gutters, elimination of larvae breeding site and intermittent preventive treatment with sulfadoxine–pyrimethamine (IPTp-SP) in pregnant women were also known by the auxiliaries, respectively 99.8% and 77.4%. However, the malaria pathogen (25.1%) and the NMCP recommendations (e.g. use of AL or AS + AQ as first-line treatment for uncomplicated malaria and IPTp-SP in pregnant women) were not well known by the auxiliaries (28.2% and 26.9% for uncomplicated and severe malaria). Concerning the practices of the auxiliaries, 91.1% offered anti-malarial drugs to patients without a prescription and 47.3% mentioned incorrect dosages. The combination artemether + lumefantrine was the most recommended (91.3%). The delivery of anti-malarial drugs was rarely accompanied by advice on malaria prevention, neither was it carried out on the result of an RDT.ConclusionThe epidemiology and the NMCP recommendations for the diagnostic and therapeutic management of malaria, are not well known to auxiliaries, which may have implications for their practices. These results show the need to sensitize and train private pharmacy auxiliaries, and also to involve them in NMCP activities.

Differential insecticide resistance in Anopheles arabiensis populations in the seaside area of Mbour and its suburbs in Senegal

Regular monitoring of insecticide resistance status is an important step in implementing appropriate and adapted insecticide-based strategies for vector control. In Senegal, Indoor Residual Spraying (IRS) and a national distribution campaign for long-lasting insecticide-treated net (LLIN) have been implemented since 2007 and 2009, respectively to prevent malaria transmission. To expand and ensure the sustainability of these strategies, we conducted a study on the status of insecticide resistance in malaria vectors in the seaside area of Mbour and its suburbs where no data were previously available.Anopheles larvae were sampled from four study sites (two in both coastal and inland areas) and reared to adulthood in the insectarium. Non-blood-fed females aged 3–5 days were then tested for susceptibility to permethrin, deltamethrin, lambdacyhalothrin, bendiocarb and pirimiphos-methyl. PCR amplification was used to identify sibling species of the An. gambiae complex and genotyping for the presence of resistance knockdown (kdr) L1014S, L1014F and Ace-1 G119S.Anopheles arabiensis was the only species present in the area. At all four sites, mosquitoes were resistant to deltamethrin, permethrin, and lambdacyhalothrin, and exhibited varying degrees of resistance to bendiocarb and pirimiphos-methyl. Overall, high levels of leucine-serine/phenylalanine substitutions at position 1014 (L1014S/L1014F) were observed, with frequencies ranging from 76.4 to 85.2 % for L1014F, and from 43.2 to 66.7 % for L1014S, compared to 8.1 to 28.3 for the Ace-1 G119S mutation.These results indicate a high level of phenotypic and genotypic resistance to insecticides, which is alarming, as it could have a significant impact on the operational effectiveness of current vector control tools that rely on pyrethroids. However, in the case of bendiocarb and pirimiphos-methyl, while some level of tolerance was observed, their potential use requires regular monitoring to prevent operational failure, as their deployment could potentially lead to an increase in resistance to them.

Long-Lasting Insecticide-Treated Nets Combined or Not with Indoor Residual Spraying May Not Be Sufficient to Eliminate Malaria: A Case-Control Study, Benin, West Africa.

In sub-Saharan Africa, despite the implementation of multiple control interventions, the prevalence of malaria infection and clinical cases remains high. The primary tool for vector control against malaria in this region is the use of long-lasting insecticide-treated nets (LLINs) combined or not with indoor residual spraying (IRS) to achieve a synergistic effect in protection. The objective of this study was to assess the effectiveness of LLINs, with or without IRS, protected against Plasmodium falciparum infection and uncomplicated clinical cases (UCC) of malaria in Benin. A case-control study was conducted, encompassing all age groups, in the urban area of Djougou and the rural area of Cobly. A cross-sectional survey was conducted that included 2080 individuals in the urban area and 2770 individuals in the rural area. In the urban area, sleeping under LLINs did not confer significant protection against malaria infection and UCC when compared to no intervention. However, certain neighbourhoods benefited from a notable reduction in infection rates ranging from 65% to 85%. In the rural area, the use of LLINs alone, IRS alone, or their combination did not provide additional protection compared to no intervention. IRS alone and LLINs combined with IRS provided 61% and 65% protection against malaria infection, respectively, compared to LLINs alone. The effectiveness of IRS alone and LLINs combined with IRS against UCC was 52% and 54%, respectively, when compared to LLINs alone. In both urban and rural areas, the use of LLINs alone, IRS alone, and their combination did not demonstrate significant individual protection against malaria infection and clinical cases when compared to no intervention. In the conditions of this study, LLINs combined or not with IRS are not effective enough to eliminate malaria. In addition to the interventions, this study identified factors associated with malaria in Benin as housing design, neglected social groups like gender-marginalised individuals and adolescents, and socio-economic conditions acting as barriers to effective malaria prevention. Addressing these factors is crucial in order to facilitate malaria elimination efforts in sub-Saharan Africa.

Analysing the progress in service delivery towards achieving universal health coverage in Nigeria: a scoping review

BackgroundAttainment of universal health coverage (UHC) requires optimal utilization of health services. Poor coverage and inequitable access to healthcare could hinder improvement in service delivery towards UHC. The study analyzed the progress in service delivery coverage and equity in access to care within the Nigerian health systems based on the tracer indicators of the WHO framework for monitoring UHC.MethodsWe searched the literature in databases: PubMed, Scopus, Directory of Open Access Journals, Google Scholar, Science Direct and websites of relevant health Ministries, Agencies, and Organizations between March to December 2022. Search terms were identified in four broader themes: Service delivery coverage, equity, UHC and Nigeria. Data were collected through a review of 37 published articles (19 peer-reviewed articles and 8 grey documents). We synthesized the findings in thematic areas using the WHO framework for monitoring UHC.ResultsThe findings show a slow improvement in service delivery coverage across the UHC tracer indicators; reproductive, maternal, newborn and child health, infectious diseases, non-communicable diseases and service capacity and access. With regards to equity in access to care across the tracer indicators, there has been a great disparity in the utilization of healthcare services among rural dwellers, lower educational level individuals and those with poor socio-economic status over 20 years. However, there was remarkable progress in the ownership and use of long-lasting insecticide-treated nets among rural and lowest-wealth quantile households than their urban counterpart.ConclusionThere is poor coverage and persistent inequitable access to care among the tracer indicators for monitoring progress in service delivery. Attaining UHC requires concerted efforts and investment of more resources in service delivery to address inequitable access to care and sustainable service coverage for improved health outcomes.

Bifurcation analysis and global sensitivity index for malaria disease transmission dynamics: Information and treated bed nets control

Malaria is known globally as the foremost cause of death in children and adults. Several intervention strategies and controls have been implemented and proposed, among which is Long Lasting Insecticide Treated Nets (LLINs). Malaria cases have been reported to reduce by [Formula: see text] due to the use of LLINs. However, the laid-back behaviors of humans negatively impact its effective use through improper handling and exposure to direct sunlight. To this end, a mathematical model is formulated to investigate the influence of individual response to information on the transmission dynamics of malaria infection in both human and mosquito populations. The threshold for the effective reduction of the prevalence of malaria through a behavioral change in the use of LLINs in response to the created awareness is determined in this study. The point of departure of this study from other studies is that it incorporates information/awareness as a dynamic variable to investigate the impact of LLINs on malaria. The equilibrium points of the model are analyzed using stability theory and the associated basic reproduction number [Formula: see text]. The implicit function theorem is used to determine the direction of bifurcation. We use Latin hypercube sampling (LHS) to test the most sensitive parameters in the basic reproduction number. The correlation between the [Formula: see text] and parameters is displayed using Scatter plots. The mathematical analysis shows that the direction of bifurcation is supercritical, which suggests that we only need to bring [Formula: see text] below unity for disease eradication. The study also revealed that an increase in awareness of the use of LLINs has an impact on reducing malaria transmission.

Prompt treatment-seeking behaviour varies within communities among guardians of children with malaria-related fever in Malawi

BackgroundIn Malawi, malaria is responsible for 40% of hospital deaths. Prompt diagnosis and effective treatment within 24 h of fever onset is critical to prevent progression from uncomplicated to severe disease and to reduce transmission.MethodsAs part of the large evaluation of the malaria vaccine implementation programme (MVIP), this study analysed survey data to investigate whether prompt treatment-seeking behaviour is clustered at community-level according to socio-economic demographics.ResultsFrom 4563 households included in the survey, 4856 children aged 5–48 months were enrolled. Out of 4732 children with documented gender, 52.2% were female and 47.8% male. Among the 4856 children, 33.8% reported fever in the two weeks prior to the survey. Fever prevalence was high in communities with low socio-economic status (SES) (38.3% [95% CI: 33.7–43.5%]) and low in areas with high SES (29.8% [95% CI: 25.6–34.2%]). Among children with fever, 648 (39.5%) sought treatment promptly i.e., within 24 h from onset of fever symptoms. Children were more likely to be taken for prompt treatment among guardians with secondary education compared to those without formal education (aOR:1.37, 95% CI: 1.11–3.03); in communities with high compared to low SES [aOR: 2.78, 95% CI: 1.27–6.07]. Children were less likely to be taken for prompt treatment if were in communities far beyond 5 km to health facility than within 5 km [aOR: 0.44, 95% CI: 0.21–0.92].ConclusionThe high heterogeneity in prevalence of fever and levels of prompt treatment-seeking behaviour underscore the need to promote community-level malaria control interventions (such as use of long-lasting insecticide-treated nets (LLINs), indoor residual spraying (IRS), intermittent preventive therapy (IPT), presumptive treatment and education). Programmes aimed at improving treatment-seeking behaviour should consider targeting communities with low SES and those far from health facility.

Topical repellents for malaria prevention.

Insecticide-based interventions, such as long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS), remain the backbone of malaria vector control. These interventions target mosquitoes that prefer to feed and rest indoors, but have limited capacity to prevent transmission that occurs outdoors or outside regular sleeping hours. In low-endemicity areas, malaria elimination will require that these control gaps are addressed, and complementary tools are found. The use of topical repellents may be particularly useful for populations who may not benefit from programmatic malaria control measures, such as refugees, the military, or forest goers. This Cochrane Review aims to measure the effectiveness of topical repellents to prevent malaria infection among high- and non-high-risk populations living in malaria-endemic regions. To assess the effect of topical repellents alone or in combination with other background interventions (long-lasting insecticide-treated nets, or indoor residual spraying, or both) for reducing the incidence of malaria in high- and non-high-risk populations living in endemic areas. We searched the following databases up to 11 January 2023: the Cochrane Infectious Diseases Group Specialised Register; CENTRAL (in the Cochrane Library); MEDLINE; Embase; CAB Abstracts; and LILACS. We also searched trial registration platforms and conference proceedings; and contacted organizations and companies for ongoing and unpublished trials. We included randomized controlled trials (RCTs) and cluster-randomized controlled trials (cRCTs) of topical repellents proven to repel mosquitoes. We also included non-randomized studies that complied with pre-specified inclusion criteria: controlled before-after studies (CBA), controlled interrupted time series (ITS), and controlled cross-over trials. Four review authors independently assessed trials for inclusion, and extracted the data. Two authors independently assessed the risk of bias (RoB) using the Cochrane RoB 2 tool. A fifth review author resolved any disagreements. We analysed data by conducting a meta-analysis, stratified by whether studies included populations considered to be at high-risk of developing malaria infection (for example, refugees, forest goers, or deployed military troops). We combined results from cRCTs with RCTs by adjusting for clustering and presented results using forest plots. We used the GRADE framework to assess the certainty of the evidence. We only included data on Plasmodium falciparum infections in the meta-analysis. Thirteen articles relating to eight trials met the inclusion criteria and were qualitatively described. We included six trials in the meta-analysis (five cRCTs and one RCT). Effect on malaria incidence Topical repellents may slightly reduce P falciparum infection and clinical incidence when both outcomes are considered together (incidence rate ratio (IRR) 0.74, 95% confidence interval (CI) 0.56 to 0.98; 3 cRCTs and 1 RCT, 61,651 participants; low-certainty evidence); but not when these two outcomes were considered independently. Two cRCTs and one RCT (12,813 participants) evaluated the effect of topical repellents on infection incidence (IRR 0.76, 95% CI 0.56 to 1.02; low-certainty evidence). One cRCT (48,838 participants) evaluated their effect on clinical case incidence (IRR 0.66, 95% CI 0.32 to 1.36; low-certainty evidence). Three studies (2 cRCTs and 1 RCT) included participants belonging to groups considered at high-risk of being infected, while only one cRCT did not include participants at high risk. Adverse events Topical repellents are considered safe. The prevalence of adverse events among participants who used topical repellents was very low (0.6%, 283/47,515) and limited to mild skin reactions. Effect on malaria prevalence Topical repellents may slightly reduce P falciparum prevalence (odds ratio (OR) 0.81, 95% CI 0.67 to 0.97; 3 cRCTs and 1 RCT; 55,366 participants; low-certainty evidence). Two of these studies (1 cRCT and 1 RCT) were carried out in refugee camps, and included exclusively high-risk populations that were not receiving any other background vector control intervention. There is insufficient evidence to conclude that topical repellents can prevent malaria in settings where other vector control interventions are in place. We found the certainty of evidence for all outcomes to be low, primarily due to the risk of bias. A protective effect was suggested among high-risk populations, specially refugees, who might not have access to other standard vector control measures. More adequately powered clinical trials carried out in refugee camps could provide further information on the potential benefit of topical repellents in this setting. Individually randomized studies are also likely necessary to understand whether topical repellents have an effect on personal protection, and the degree to which diversion to non-protected participants affects overall transmission dynamics. Despite this, the potential additional benefits of topical repellents are most likely limited in contexts where other interventions are available.

Characterisation of Anopheles species composition and genetic diversity in Meghalaya, northeast India, using molecular identification tools.

Malaria in India is declining, in part due to the use of long-lasting insecticide-treated nets (LLINs) and vector control. Historically, the north-eastern region of India has contributed ~10%-12% of the nation's malaria burden. The important mosquito vectors in northeast India have long been considered to be Anopheles baimaii and An. minimus, both associated with forest habitats. Local deforestation and increased rice cultivation, along with widespread LLIN use, may be changing vector species composition. Understanding if and how vector species composition is changing is critical to successful malaria control. In Meghalaya state, malaria is now at a low level of endemicity with occasional seasonal outbreaks. In a biodiverse setting like Meghalaya, where >24 Anopheles mosquito species have been recorded, accurate morphological identification of all species is logistically challenging. To accurately determine Anopheles species richness in the West Khasi Hills (WKH) and West Jaintia Hills (WJH) districts, adult and larval mosquitoes were collected and identified using molecular methods of allele-specific PCR and cytochrome oxidase I DNA barcoding. In 14 villages across both districts, we identified high species richness, 19 species in total. Molecular findings indicated that An. minimus and An. baimaii were rare, while four other species (An. maculatus, An. pseudowillmori, An. jeyporiensis and An. nitidus) were abundant. Anopheles maculatus was highly prevalent in WKH (39% of light trap collections) and An. pseudowillmori in WJH (45%). Larvae of these four species were found in rice fields, suggesting that land cover change is influencing species composition change. Our results suggest that rice fields might be contributing to the observed abundance of An. maculatus and An. pseudowillmori, which could be playing a role in malaria transmission, either independently due to their high abundance, or in combination with An. baimaii and/or An. minimus.

Epidemiology of malaria, schistosomiasis, and geohelminthiasis amongst children 3-15 years of age during the dry season in Northern Cameroon.

The double burden of malaria and helminthiasis in children poses an obvious public health challenge, particularly in terms of anemia morbidity. While both diseases frequently geographically overlap, most studies focus on mono-infection and general prevalence surveys without molecular analysis. The current study investigated the epidemiological determinants of malaria, schistosomiasis, and geohelminthiasis transmission among children in the North Region of Cameroon. School and pre-school children aged 3-15 year-of-age were enrolled from three communities in March 2021 using a community cross-sectional design. Capillary-blood samples were obtained, and each was examined for malaria parasites using rapid-diagnostic-test (RDT), microscopy, and PCR while hemoglobin level was measured using a hemoglobinometer. Stool samples were analyzed for Schistosoma mansoni, S. guineensis, and soil-transmitted-helminthiasis (STH) infections using the Kato Katz method, and urine samples were assessed for the presence of S. haematobium eggs (including hybrids) using the standard urine filtration technique. A malaria prevalence of 56% (277/495) was recorded by PCR as opposed to 31.5% (156/495) by microscopy and 37.8% (186/495) by RDT. Similarly, schistosomiasis was observed at prevalence levels of up to 13.3% (66/495) overall [S. haematobium (8.7%); S. mansoni (3.8%); mixed Sh/Sm (0.6%); mixed Sh/Sm/Sg (0.2%). Both infections were higher in males and the 3-9 year-of-age groups. A high frequency of PCR reported P. falciparum mono-infection of 81.9% (227/277) and mixed P. falciparum/P. malariae infection of 17.3% (48/277) was observed. Malaria-helminths co-infections were observed at 13.1% (65/495) with marked variation between P. falciparum/S. haematobium (50.8%, 33/65); P. falciparum/S. mansoni (16.9%, 11/65) and P. falciparum/Ascaris (9.2%, 6/65) (χ2 = 17.5, p = 0.00003). Anemia prevalence was 32.9% (163/495), categorically associated with P. falciparum (45.8%, 104/227), Pf/Sh (11.5%, 26/227), and Pf/Sm (3.9%, 9/227) polyparasitism. Polyparasitism with malaria and helminth infections is common in school-aged children despite periodic long-lasting insecticide-treated nets (LLINs) distribution and regular school-based praziquantel (for schistosomiasis) and albendazole (for STH) campaigns. Co-existence of Plasmodium parasites and helminths infections notably Schistosoma species among children may concurrently lead to an increase in Plasmodium infection with an enhanced risk of anemia, highlighting the necessity of an integrated approach for disease control interventions.

Assessing afebrile malaria and bed-net use in a high-burden region of India: Findings from multiple rounds of mass screening.

A key obstacle in the fight against malaria is afebrile malaria. It remains undiagnosed and, therefore, is invisible to the health system. Apart from being a serious illness, it contributes to increased transmission. Existing studies in India have not adequately reported afebrile malaria and its determinants, including the use of long-lasting insecticide-treated nets (LLINs). This study used six waves of mass screening, which were conducted by the state government in the high-malaria-burden region of Chhattisgarh, a state in India, in 2020, 2021, and 2022. Each round of data collection included more than 15000 individuals. Descriptive statistics were used to analyse key indicators of malaria prevalence and LLIN use. Multivariate analyses were performed to identify the determinants of afebrile malaria and LLIN use. Malaria prevalence in the afebrile population varied from 0.6% to 1.4% across the different waves of mass screening. In comparison, malaria positivity among febrile individuals was greater than 33% in each wave. Afebrile malaria contributed to 19.6% to 47.2% of the overall malaria burden in the region. Indigenous communities (scheduled tribes) were more susceptible to malaria, including afebrile malaria. Individuals using LLINs were less likely to be affected by afebrile malaria. Overall, 77% of the individuals used LLINs in early monsoon season, and in winter the rate was lower at 55%. LLIN use was significantly associated with the number of LLINs the households received from the government. Although fever continues to be a primary symptom of malaria, afebrile malaria remains a significant contributor to the malaria burden in the region. The free distribution of LLINs should be expanded to include high-burden populations. Global policies must include strategies for surveillance and control of afebrile malaria in high-burden areas.

Can insecticide resistance increase malaria transmission? A genetics-epidemiology mathematical modeling approach.

The great successes recorded in the fight against malaria over the last two decades, resulting from the wide scale implementation of insecticide-based interventions in malaria-endemic areas, has prompted a renewed global effort to eradicate malaria. The widespread emergence of insecticide resistance in the population of adult female malaria mosquitoes is considered to pose a potential challenge to such effort. In this study, we address one of the key questions in malaria ecology, namely whether or not insecticide resistance increase malaria transmission. We developed a genetics-epidemiology modeling framework that incorporates a detailed genotype structure of the gene that confers insecticide resistance in mosquitoes, malaria epidemiology in mosquitoes and humans (stratified based on whether or not they are protected by Long-lasting insecticide-treated nets (LLINs) indoors), genotype-specific mosquito repellance property of LLINs and mosquito biting behavior (indoor and outdoor bites). Conditions for the existence and local asymptotic stability of the various disease-free equilibria (by genotype) of the resulting genetic-epidemiology model are derived. This study identifies four parameters of the model that play a crucial role on quantifying the impact of insecticide resistance on malaria transmission, namely the parameters related to the level of the dominance of the resistant allele in heterozygous mosquitoes, the coverage of long-lasting insecticidal nets in the community, the probability of endophilic mosquitoes to successfully take a bloodmeal indoors and the proportion of new adult mosquitoes that are endophilic. We showed that, depending on the values of these four identified parameters, insecticide resistance can increase, decrease, or have no effect on malaria transmission. Our simulations show that malaria eradication can indeed be achieved using the currently-available chemical insecticides, even in the wake of the prevailing widespread insecticide resistance in malaria-endemic areas, if the insecticide-based interventions implemented can result in the attainment of the optimal values of the four identified parameters in malaria-endemic areas.

Exploring The Experiments of Mass Distributions of Bed Nets in The Community to Prevent Malaria in Kisantu Health Zone, Democratic Republic of Congo: A Qualitative Study

Despite its discovery more than a century, malaria remains a of public health problem. One of the pillars in the strategy to fighting it is the use of the mosquito net, which remains the only significant tool of prevention. This study is to evaluate the knowledge, perception and experiments of the mass campaign distribution of the mosquito nets in the community one year after the distribution. A qualitative study, centered on households, was carried out in the community of Kisantu Health Zone (KHZ) in the end of clinical trial in 2019. The semi-structured interviews with community leaders and individual focus groups with women having at least one child, were selected in six villages of the of KHZ. Among the respondents, the all had a good level of knowledge of mosquito nets, namely the proper definition of a mosquito net, the correct mode of installation in a sleeping space and that the occurrence of such holes in a mosquito net could be repaired but that was grounds for its inefficiency. The minority either cleaned the mosquito net with powdered laundry soap, and spread out to dry under the sun. The undesirable events related to the use of long-lasting insecticide-treated nets (LLINs) as well as occurrence of holes was quoted by a minority of the respondents as grounds of the weak use of LLINs in households. After one year of distribution, majority possession and the minority gave up use because of attrition or an adverse effect allotted to the use of LLINs.

Semi-field evaluation of a volatile transfluthrin-based intervention reveals efficacy as a spatial repellent and evidence of other modes of action.

Presently, the most common malaria control tools-i.e., long lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS)-are limited to targeting indoor biting and resting behaviors of Anopheles mosquito species. Few interventions are targeted towards malaria control in areas where transmission is driven or persists due to outdoor biting behaviors. This study investigated a volatile pyrethroid-based spatial repellent (VPSR) designed to bridge this gap and provide protection from mosquito bites in outdoor spaces. Southern Province, Zambia, is one such environment where outdoor biting is suspected to contribute to malaria transmission, where people are active in the evening in open-walled outdoor kitchens. This study assessed the VPSR in replica kitchens within a controlled semi-field environment. Endpoints included effects on mosquito host seeking, immediate and delayed mortality, deterrence, blood feeding inhibition, and fertility. Host-seeking was reduced by approximately 40% over the course of nightly releases in chambers containing VPSR devices. Mosquito behavior was not uniform throughout the night, and the modeled effect of the intervention was considerably higher when hourly catch rates were considered. These two observations highlight a limitation of this overnight semi-field design and consideration of mosquito circadian rhythms is recommended for future semi-field studies. Additionally, deterrence and immediate mortality were both observed in treatment chambers, with evidence of delayed mortality and a dose related response. These results demonstrate a primarily personal protective mode of action with possible positive and negative community effects. Further investigation into this primary mode of action will be conducted through a field trial of the same product in nearby communities.

Bed-nets Hour Density after a Usage of Three Years of Long-lasting Insecticide-treated Nets in Malaria re-elimination Areas in Ngadirejo Village, Purworejo District, Indonesia

Background: Malaria, caused by the genus Plasmodium, is still a global health problem. Its transmission and spread are strongly influenced by the presence of the Anopheles vector. One of the efforts to reduce cases is the distribution of long-lasting insecticide-treated nets to the residents of malaria-endemic areas. This study aims to measure the density of mosquitoes perched on insecticide-treated bed nets after three years of usage. Method: A cross-sectional study was conducted to observe mosquitoes perching on insecticide-treated bed nets at night and calculation of mosquito density data in units of mosquitoes/LLINs/hour. Results: The number of mosquito bites before bedtime in respondents reached 72.5%, while the number of bed nets infested with mosquitoes reached 74.4%. The density of mosquitoes perched varied between 1 and 10 mosquitoes/LLINs/hour with the highest density proportion of 3 mosquitoes/LLINs/hour. Conclusion: LLINs that have been used for three years were found to be less effective at killing and preventing mosquitoes. It is advisable to re-dip with the insecticide doses to match the local vector susceptibility level by officer assistance so that the mosquito nets still function properly

Effectiveness of field-exposed attract-and-kill devices against the adults of Popillia japonica (Coleoptera: Scarabaeidae): a study on duration, form and storage.

The Japanese beetle Popillia japonica Newman is an insect pest native to Japan that has spread into North America, the Azores and, recently, into continental Europe. Here, we present a study assessing the effectiveness of a long-lasting insecticide-treated net (LLIN), assembled in semiochemical-baited attract-and-kill devices (A&Ks) as a low environmental impact means to control P. japonica in the field. We compared the attractiveness of three different forms of A&Ks that were left outdoors throughout the summer, and the residence time of P. japonica landing on them. Moreover, we performed a preliminary study testing the effectiveness of new LLINs after storage. Collected data also allowed us to investigate the beetles' diel flight patterns in relation to meteorological conditions. Killing effectiveness of the field-exposed A&Ks declined steadily over the flight season (from 100% to 37.5%) associated with a decrease in residues of α-cypermethrin, the active ingredient in the LLINs. The different A&K forms (pyramidal, octahedral and ellipsoidal) attracted similar numbers of beetles. Individual beetles' residence time ranged from 75 to 95 s and differed slightly between A&K forms. Effectiveness of LLINs decreased by ≈30% after 1 year storage. Based on numbers landing on A&Ks, the beetles' flight activity peaked about 14:30 h and was inversely correlated with relative humidity. This study indicates that semiochemical-baited A&Ks are effective for controlling P. japonica in the field. Because of active ingredient decay, the LLINs should be replaced after 30-40 days of field exposure to ensure that the A&Ks remain fully functional. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Acceptance and Utilization of Long-Lasting Insecticide-Treated Nets (LLINs) by the Community of Mamboro Sub-district and Katiku Tana Sub-district, Central Sumba Regency, East Nusa Tenggara

Distribution of mosquito nets is one healthcare strategy implemented to control the number of malaria cases in Indonesia. East Nusa Tenggara is one of the provinces contributing to high malaria rates. Cases are high in several areas, including Central Sumba regency. This study aimed to describe the behavior of the people of Mamboro and Katiku Tana sub-districts in using long-lasting insecticide-treated nets (LLINs), the number of LLINs owned, number of beds, number of family members, number of pregnant women and toddlers, distribution of LLINs in families, and LLINs utilization. This is a descriptive quantitative study with a cross-sectional design. The research was conducted in the work area of the Mananga Health Center of Susu Wendewa village of Mamboro sub-district and Malinjak Health Center of Makata Keri village of Katiku Tana sub-district, Central Sumba regency. The research was carried out from 9–19 September 2021 with 341 heads of families as respondents. Data were collected using questionnaires and in-depth interviews. Most families had LLINs (n=287; 94.1%); the total number of LLINs owned was 341, used by 1,220 (94.7%) family members with ten pregnant women and 35 children under five. The number of installed LLINs was 290 units (85%), LLINs obtained from the health centers within 1–3 months was 44% (126 families), 314 units (92%) were used while sleeping, and there were still family members who did not use LLINs every night. We conclude that the acceptance and utilization of LLINs should not stop at the distribution of LLINs to the public and must be supported by an evaluation in the form of regular surveys to ensure that LLINs are correctly used.

The ability of Anopheles funestus and A. arabiensis to penetrate LLINs and its effect on their mortality.

Background: Variation in mosquito body size and the ability to penetrate long-lasting insecticide-treated nets (LLINs) remains unknown. This study evaluated the ability of Anopheles funestusand A. arabiensis to penetrate commercially available treated and untreated bednets and how this behaviour affects mosquito mortality. Methods: Three types of LLINs; DawaPlus 2.0, PermaNet 2.0, Olyset 2.0, and untreated (Safi Net) were tested inside a semi-field system. One hundred 3-5-day-old and non-starved female A. funestus and A. arabiensis were released in a chamber with a sleeping adult volunteer under a treated or untreated bednet. Mosquitoes that penetrated inside the nets were collected every two hours using a mouth aspirator. Live mosquitoes were put in paper cups, fed on glucose ad libitum and their mortality rate was monitored for 48 h. Results: The ability of A. funestus to penetrate treated and untreated bednets was significantly higher than for A. arabiensis for all three LLIN net types ( P<0.001). For both species the penetration rate was higher for untreated bednets than treated ones except for the Olyset net. Regardless of the assessed mosquito species, all the mosquitoes that penetrated the net, successfully blood-fed on the sleeping volunteer. Compared to A. arabiensis, significant mortality was recorded for A. funestus that were caught inside Olyset nets within 48 hrs of monitoring ( P<0.001). Conclusions: These findings demonstrate the ability of A. funestus and A. arabiensis mosquitoes to penetrate the human-occupied treated and untreated bednets. Despite this ability, mosquitoes that penetrated the bednet succumbed to death within two days.

An evaluation of LLIN ownership, access, and use during the Magude project in southern Mozambique.

The Magude Project assessed the feasibly of eliminating malaria in a low transmission setting in southern Mozambique using a package of interventions. This study measured the ownership, access and use of long-lasting insecticide treated nets (LLINs) and inequalities in these indicators across household wealth, size and population subgroups, to understand the protection that LLINs provided during the project. Data were obtained from various household surveys. At least 31% of the nets distributed during the 2014 and 2017 campaigns were lost during the first year post-distribution. Most nets (77.1%) present in the district were Olyset Nets. LLIN access never exceeded 76.3% and use varied seasonally between 40% and 76.4%. LLIN access limited LLIN use during the project, especially during the high transmission season. LLIN ownership, access and use were lower in harder-to-reach localities, in poorer and larger households. Children and women below 30 had poorer access to LLINs than the overall population. Net use was lowest among school-aged children and young adults, especially among young males, and highest in children under 5, pregnant women, in older adults and in households that received indoor residual spraying (IRS). This study revealed that LLIN mass-distribution campaigns alone are not sufficient to achieve the high level of net protection needed during elimination programs and that reviewing the LLIN allocation scheme, top-up distributions and/or community engagement campaigns is needed, also to reduce inequalities in populations' access to LLINs.