Mosquitocidal effect of ivermectin-treated nettings and sprayed walls on Anopheles gambiae s.s.

Ivermectin (IVM) has been proposed as a new tool for malaria control as it is toxic on vectors feeding on treated humans or cattle. Nevertheless, IVM may have a direct mosquitocidal effect when applied on bed nets or sprayed walls. The potential for IVM application as a new insecticide for long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) was tested in this proof-of-concept study in a laboratory and semi-field environment. Laboratory-reared, insecticide-susceptible Kisumu Anopheles gambiae were exposed to IVM on impregnated netting materials and sprayed plastered- and mud walls using cone bioassays. The results showed a direct mosquitocidal effect of IVM on this mosquito strain as all mosquitoes died by 24 h after exposure to IVM. The effect was slower on the IVM-sprayed walls compared to the treated nettings. Further work to evaluate possibility of IVM as a new insecticide formulation in LLINs and IRS will be required.

Physical and insecticidal durability of Interceptor®, Interceptor® G2, and PermaNet® 3.0 insecticide-treated nets in Burkina Faso: results of durability monitoring in three sites from 2019 to 2022.

BACKGROUND: National Malaria Programmes (NMPs) monitor the durability of insecticide-treated nets (ITNs) to inform procurement and replacement decisions. This is crucial for new dual active ingredients (AI) ITNs, for which less data is available. Pyrethroid-only ITN (Interceptor®) and dual AI (Interceptor® G2, and PermaNet® 3.0) ITNs were assessed across three health districts over 36 months in southern Burkina Faso to estimate median ITN survival, insecticidal efficacy, and to identify factors contributing to field ITN longevity. METHODS: Durability was monitored through a prospective study of a cohort of nets distributed during the 2019 mass campaign. Three health districts were selected for their similar pyrethroid-resistance, environmental, epidemiological, and population profiles. Households were recruited after the mass campaign, with annual household questionnaire follow-ups over three years. Each round, ITNs were withdrawn for bioassays and chemical residue testing. Key measures were the percentage of cohort ITNs in serviceable condition, insecticidal effectiveness, and chemical residue content against target dose. Cox proportional hazard models were used to identify determinants influencing ITN survival. RESULTS: At endline, the median useful life was 3.2 (95% CI 2.5-4.0) years for PermaNet® 3.0 ITNs in Orodara, 2.6 (95% CI 1.9-3.2) years for Interceptor® G2 ITNs in Banfora and 2.4 (95% CI 1.9-2.9) years for Interceptor® ITNs in Gaoua. Factors associated with ITN survival included cohort ITNs from Orodara (adjusted hazard ratio (aHR) = 0.58, p = 0.026), households seeing less rodents (aHR = 0.66, p = 0.005), female-headed households (aHR = 0.66, p = 0.044), exposure to social behavior change (SBC) messages (aHR = 0.52, ≤ 0.001) and folding nets when not in use (aHR = 0.47, p < 0.001). At endline, PermaNet® 3.0 ITN recorded 24-h mortality of 26% against resistant mosquitos on roof panels, with an 84% reduction in PBO content. Interceptor® G2 ITN 72-h mortality was 51%, with a 67% reduction in chlorfenapyr content. Interceptor® ITN 24-h mortality was 71%, with an 84% reduction in alpha-cypermethrin content. CONCLUSION: Only PermaNet® 3.0 ITNs surpassed the standard three-year survival threshold. Identified protective factors should inform SBC messaging. Significant decreases in chemical content and resulting impact on bioefficacy warrant more research in other countries to better understand dual AI ITN insecticidal performance.

Insufficient duration of insecticidal efficacy of Yahe® insecticide-treated nets in Papua New Guinea.

BACKGROUND: Insecticide-treated nets (ITNs) are the backbone of anti-malarial vector control in Papua New Guinea (PNG). Over recent years the quality and performance of ITNs delivered to PNG decreased, which has likely contributed to the stagnation in the malaria control effort in the country. The present study reports results from the first 24 months of a durability study with the ITN product Yahe LN® in PNG. METHODS: The durability study was conducted in four villages on the northern coast of PNG, in an area with high malaria parasite transmission, following WHO-recommended methodology adapted to the local scenario. A cohort of n = 500 individually identifiable Yahe® ITNs was distributed by the PNG National Malaria Control Programme from October to December 2021. Insecticidal efficacy of the ITNs was tested using cone bioassays with fully pyrethroid susceptible Anopheles farauti colony mosquitoes at baseline and at 6 months intervals, alongside evaluation of physical integrity and the proportion of ITNs lost to follow-up. A questionnaire was used to collect information on ITN end user behaviour, such as the frequency of use and washing. The observations from the durability study were augmented with simulated laboratory wash assays. RESULTS: Gradual uptake and replacement of previous campaign nets by the communities was observed, such that at 6 months 45% of all newly distributed nets were in use in their designated households. Insecticidal efficacy of the Yahe® nets, expressed as the percent 24 h mortality in cone bioassays decreased from 91 to 45% within the first 6 months of distribution, even though > 90% of study nets had never been washed. Insecticidal efficacy decreased further to < 20% after 24 months. ITNs accumulated physical damage (holes) at a rate similar to previous studies, and 35% were classified as 'too torn' by proportional hole index after 24 months. ITNs were lost to follow-up such that 61% of cohort nets were still present after 24 months. Laboratory wash assays indicated a rapid reduction in insecticidal performance with each consecutive wash such that average 24 h mortality was below 20% after 10 washes. CONCLUSION: Yahe® ITNs are not performing as per label claim in an area with fully pyrethroid susceptible vectors, and should be investigated more comprehensively and in other settings for compliance with currently recommended durability and efficacy thresholds. The mass distribution of low quality ITN products with variable performance is one of the major ongoing challenges for global malaria control in the last decade.

LLIN Evaluation in Uganda Project (LLINEUP): modelling the impact of COVID-19-related disruptions on delivery of long-lasting insecticidal nets on malaria indicators in Uganda.

BACKGROUND: Disruptions in malaria control due to COVID-19 mitigation measures were predicted to increase malaria morbidity and mortality in Africa substantially. In Uganda, long-lasting insecticidal nets (LLINs) are distributed nationwide every 3-4 years, but the 2020-2021 campaign was altered because of COVID-19 restrictions so that the timing of delivery of new nets was different from the original plans made by the National Malaria Control Programme. METHODS: A transmission dynamics modelling exercise was conducted to explore how the altered delivery of LLINs in 2020-2021 impacted malaria burden in Uganda. Data were available on the planned LLIN distribution schedule for 2020-2021, and the actual delivery. The transmission model was used to simulate 100 health sub-districts, and parameterized to match understanding of local mosquito bionomics, net use estimates, and seasonal patterns based on data collected in 2017-2019 during a cluster-randomized trial (LLINEUP). Two scenarios were compared; simulated LLIN distributions matching the actual delivery schedule, and a comparable scenario simulating LLIN distributions as originally planned. Model parameters were otherwise matched between simulations. RESULTS: Approximately 70% of the study population received LLINs later than scheduled in 2020-2021, although some areas received LLINs earlier than planned. The model indicates that malaria incidence in 2020 was substantially higher in areas that received LLINs late. In some areas, early distribution of LLINs appeared less effective than the original distribution schedule, possibly due to attrition of LLINs prior to transmission peaks, and waning LLIN efficacy after distribution. On average, the model simulations predicted broadly similar overall mean malaria incidence in 2021 and 2022. After accounting for differences in cluster population size and LLIN distribution dates, no substantial increase in malaria burden was detected. CONCLUSIONS: The model results suggest that the disruptions in the 2020-2021 LLIN distribution campaign in Uganda did not substantially increase malaria burden in the study areas.

Efficacy of pyrethroid-pyriproxyfen and pyrethroid-chlorfenapyr nets on entomological indicators of malaria transmission: third year of a randomised controlled trial in Benin.

The present cluster-randomised control trial aims to assess the entomological efficacy of pyrethroid-pyriproxyfen and pyrethroid-chlorfenapyr LLINs compared to the standard pyrethroid-only LLINs, in their third year of community usage. Adult mosquito collections were performed every 3 months, in 4 randomly selected houses in each of the 60 trial clusters, using human landing catches. Adult mosquitoes were morphologically identified and Anopheles vectors were molecularly speciated and screened for the presence of the L1014F kdr mutation using PCR. Plasmodium falciparum sporozoite infection was assessed using ELISA. A subset of An. gambiae s.l. was also dissected to examine parity and fertility rates across study arms. There was no evidence of a significant reduction in indoor vector density and entomological inoculation rate by the pyrethroid-pyriproxyfen [DR 0.94 (95% CI 0.46-1.88), p = 0.8527; and RR 1.10 (95% CI 0.44-2.72), p = 0.8380], and pyrethroid-chlorfenapyr [DR 0.74 (95% CI 0.37-1.48), p = 0.3946; and RR 1.00 (95% CI 0.40-2.50), p = 0.9957] LLINs, respectively. The same trend was observed outdoors. Frequencies of the L1014F kdr mutation, as well as parous and fertility rates, were similar between study arms. In the third year after net distribution, entomological indicators show that the two dual active-ingredients nets performed similarly to the standard pyrethroid-only LLIN. To maintain malaria gains, it is crucial that net distribution cycles fit with their operational lifespan.

The relationship between anaemia and the use of treated bed nets among pregnant and non-pregnant women in Ghana.

Studies have indicated that the risk of malaria, particularly its association with anaemia in pregnant women, increases when treated bed nets are not used. This paper utilizes a statistical mechanical model to investigate whether there is a statistical relationship between the presence or absence of anaemia in pregnant and non-pregnant women and their decision to sleep under treated bed nets. Data from the Ghana Malaria Indicator Survey (GMIS), which includes both rural and urban malaria-endemic areas in Ghana, were employed in this study. A total of 2,434 women, comprising 215 pregnant and 2,219 non-pregnant participants, were involved. Among these, 4.76% of the pregnant and anaemic women and 45.89% of the non-pregnant and anaemic women slept under treated bed nets, while 0.86% of the pregnant and anaemic and 6.82% of the non-pregnant and anaemic women did not. The findings revealed that, in the absence of social interaction, non-anaemic pregnant women have a lower prevalence of choosing to use bed nets compared to their anaemic counterparts. Additionally, non-pregnant anaemic women showed a positive private incentive (30.87%) to use treated bed nets, implying a positive correlation between anaemia and the choice to sleep in a treated bed net. Furthermore, the study demonstrated that both pregnancy and anaemia status have a relationship with the use of treated bed nets in Ghana, especially when social interactions are considered. The interaction strength between non-pregnant and anaemic women interacting with each other shows a negative estimate (-1.49%), implying that there is no rewarding effect from imitation. These insights are crucial for malaria prevention and control programs, emphasizing the need for targeted interventions to enhance the use of treated bed nets among both pregnant and non-pregnant women in Ghana's malaria-endemic regions.

A qualitative look at bed net access and use in Burkina Faso, Mozambique, Nigeria, and Rwanda following piloted distributions of dual-active ingredient insecticide-treated nets.

BACKGROUND: Universal coverage with insecticide-treated nets (ITNs) is important for malaria control and elimination. The emergence and intensification of insecticide resistance threatens progress made through the deployment of these interventions and has required the development of newer, more expensive ITN types. Understanding malaria prevention behaviour, including barriers and facilitators to net access and use, can support effective decision-making for the promotion and distribution of ITNs. METHODS: In-depth interviews and focus group discussions were conducted in 3 to 4 villages per district, in 13 districts across Burkina Faso, Mozambique, Nigeria and Rwanda from 2019 to 2022. Interviews were conducted in the local language, translated and transcribed in English, French or Portuguese. Transcripts were coded and analysed using Nvivo and ATLAS.ti. RESULTS: ITNs were obtained from mass distribution campaigns, antenatal care and immunization visits, and purchased on the private market in some locations. While there were divergent perspectives in whether the number of distributed nets were adequate, participants consistently expressed concerns of bias, discrimination, and a lack of transparency with the distribution process. ITNs were frequently used alongside other malaria prevention methods. The primary motivation for use was malaria prevention. While some participants reported using nets nightly throughout the year, other participants reported seasonal use, both due to the perceived higher density of mosquitoes and discomfort of sleeping under a net in the increased heat. Other barriers to consistent net use included activities that take place away from the home, sleeping patterns and arrangements, and sensitivity to the insecticides on the nets. CONCLUSIONS: ITNs remain an important malaria control intervention. To ensure adequate and increased net access, distribution campaigns should consider family structures, available sleeping spaces, and other bed sharing preferences when identifying the number of nets needed for distribution. In addition, campaigns should allow for multiple options for net distribution points and timing to accommodate households remote to health services. Continuous distribution channels and complimentary distribution through the private sector could help fill gaps in coverage. Solutions are needed for outdoor malaria transmission, including alternative designs for ITNs, and improving access to complementary personal protective measures.

Level of awareness and utilization of insecticide-treated bed nets among medical students as measures for reducing malaria episodes.

This study examined the level of awareness and utilization of insecticide-treated bed nets among medical students as measures for reducing malaria episodes in Delta State University, Abraka. It was a descriptive study with objectives and research questions formulated to achieve the study design. A sample size of 200 male and female students resident in the campus hostels were selected using random sampling technique. A self-structured questionnaire was designed and administered to the study participants, however, only 148 copies of the questionnaires were successfully retrieved and used for the study. Data generated were subjected to quantitative statistical analysis for frequencies, percentages, average mean and Chi-square testing. Findings revealed that the level of awareness was significantly associated with the role of health workers in the distribution of insecticide-treated bed nets in Delta State University, Abraka, although, factors hindering health workers from distributing insecticide-treated bed nets were identified. There was significant difference between perception of medical students and the utilization of insecticide-treated bed nets on risk of malaria spread. In addition, there was significant difference between the benefits of using insecticide-treated bed nets and the prevention and control of malaria. We therefore conclude that regular utilization of insecticide-treated bed nets due to adequate awareness eliminates contact with mosquitoes and prevents transmitting vectors of malaria from having contact with the users of insecticide-treated bed net. Massive health education campaign is recommended to further scale up the awareness and effective utilization of insecticide-treated bed nets towards prevention and control of malaria bites among students in Delta State University, Abraka.

Examining the paradox: increased malaria risk in children under 5 in female-headed households in Nigeria.

BACKGROUND: Nigeria is facing a severe malaria crisis, accounting for a significant proportion of global cases and deaths of malaria. This study aimed to investigate the differences between female-headed households (FHHs) and male-headed households (MHHs) and their impact on malaria risk among children under five (U5) in Nigeria. METHODS: Data from the 2021 Nigeria Malaria Indicator Survey (NMIS) were used for this cross-sectional study. A representative sample of 10,988 households was analysed, with key variables subjected to frequency calculations, descriptive statistics, and bivariate analyses using t-tests and chi-square analyses to compare the differences between FHHs and MHHs. RESULTS: Among all participants, 92.1% (N = 10,126) reported residing in male-headed households, while 7.8% (N = 862) reported living in female-headed households. MHHs were significantly more likely to own insecticide-treated bed nets (ITNs) than FHHs (64.7% vs. 53.6%, P < 0.001). U5 children in MHHs had a greater likelihood of sleeping under a bed net the night before the survey than U5 children in FHHs (35.3% vs. 30.0%, P < 0.05). The prevalence of fever in the previous two weeks among U5 children was similar in MHHs and FHHs (35.4% vs. 31.4%), and the testing rates for malaria among U5 children who experienced febrile episodes were higher in MHHs than FHHs (22.4% vs. 15.4%, P < 0.05). Although not statistically significant, FHHs exhibited a higher percentage of U5 children testing positive for malaria compared to MHHs (87.8% vs. 78.9%). On the other hand, FHHs had higher education levels, overall wealth index scores, and a larger presence in urban areas compared to MHHs (P < 0.001). Moreover, FHHs reported higher adherence to malaria prevention awareness (P < 0.001). CONCLUSION: In Nigeria, FHHs enjoy relatively better socioeconomic conditions and stronger awareness of malaria prevention compared to their male-headed counterparts. Contrary to expectations, FHHs are at an increased risk of malaria in children under 5 years old. This phenomenon is associated with entrenched gender inequality and the challenges women face in accessing critical assets. As women in FHHs bear the responsibility of income generation while caring for their children, it is crucial to prioritize interventions that address malaria management in FHHs to reduce both malaria incidence and mortality rates.

Complete series method (CSM): a convenient method to reduce daily heterogeneity when evaluating the regeneration time (RT) of insecticide-treated nets (ITNs).

BACKGROUND: "Regeneration time" (RT) denotes the time required to obtain a stable mortality rate for mosquitoes exposed to insecticide-treated nets (ITNs) after three consecutive washes of a net in a day. The RT informs the wash interval used to artificially age ITNs to simulate their lifetime performance under user conditions (20 washes). RT was estimated following World Health Organization (WHO) longitudinal method (LM) procedures. Longitudinal evaluation may introduce heterogeneity due to mosquito batch variability, complicating RT determination. To overcome this, nets at each stage of regeneration (i.e., 1, 2, 3, 5 and 7 days post wash) were prepared in advance and refrigerated; then, a complete regeneration series was tested with a single mosquito batch on 1 testing day, completing four series over 4 days. This study compared the complete series method (CSM) against the LM. METHODS: The overall heterogeneity in the methods for estimating RT of one incorporated alpha-cypermethrin and piperonyl butoxide (PBO) and one incorporated permethrin with PBO ITNs was determined using laboratory-reared resistant Anopheles arabiensis under standard laboratory conditions. LM methods and CSM were compared in two experiments with refrigerated nets acclimated for (i) 2 h (test 1) and (ii) 3 h (test 2). Four regeneration replicates per day were tested per ITN product with 50 mosquitoes exposed per replicate (equivalent sample size to LM). The heterogeneity from these methods was compared descriptively. RESULTS: The intra-method variability for unwashed pieces was minimal, with variance of 1.26 for CSM and 1.18 for LM. For unwashed nets, LM had substantially greater variance and ratio of LM:CSM was 2.66 in test 1 and 2.49 in test 2. The magnitude of mortality measured in bioassays depended on sample acclimation after refrigeration. CONCLUSIONS: The CSM is a convenient method for determining the regeneration times. ITNs are prepared in advance, reducing pressure to prepare all samples to start on a single day. A complete regeneration series of samples is removed from the refrigerator, defrosted and evaluated on a single day with one mosquito batch reducing the influence of mosquito batch heterogeneity on results. Replicates can be conducted over several days but do not have to be conducted on consecutive days, allowing easy facility scheduling.

Combined use of long-lasting insecticidal nets and Bacillus thuringiensis israelensis larviciding, a promising integrated approach against malaria transmission in northern Côte d'Ivoire.

BACKGROUND: The recent reduction in malaria burden in Côte d'Ivoire is largely attributable to the use of long-lasting insecticidal nets (LLINs). However, this progress is threatened by insecticide resistance and behavioral changes in Anopheles gambiae sensu lato (s.l.) populations and residual malaria transmission, and complementary tools are required. Thus, this study aimed to assess the efficacy of the combined use of LLINs and Bacillus thuringiensis israelensis (Bti), in comparison with LLINs. METHODS: This study was conducted in the health district of Korhogo, northern Côte d'Ivoire, within two study arms (LLIN + Bti arm and LLIN-only arm) from March 2019 to February 2020. In the LLIN + Bti arm, Anopheles larval habitats were treated every fortnight with Bti in addition to the use of LLINs. Mosquito larvae and adults were sampled and identified morphologically to genus and species using standard methods. The members of the An. gambiae complex were determined using a polymerase chain reaction technique. Plasmodium infection in An. gambiae s.l. and malaria incidence in local people was also assessed. RESULTS: Overall, Anopheles spp. larval density was lower in the LLIN + Bti arm 0.61 [95% CI 0.41-0.81] larva/dip (l/dip) compared with the LLIN-only arm 3.97 [95% CI 3.56-4.38] l/dip (RR = 6.50; 95% CI 5.81-7.29; P < 0.001). The overall biting rate of An. gambiae s.l. was 0.59 [95% CI 0.43-0.75] biting/person/night in the LLIN + Bti arm against 2.97 [95% CI 2.02-3.93] biting/person/night in LLIN-only arm (P < 0.001). Anopheles gambiae s.l. was predominantly identified as An. gambiae sensu stricto (s.s.) (95.1%, n = 293), followed by Anopheles coluzzii (4.9%; n = 15). The human-blood index was 80.5% (n = 389) in study area. EIR was 1.36 infected bites/person/year (ib/p/y) in the LLIN + Bti arm against 47.71 ib/p/y in the LLIN-only arm. Malaria incidence dramatically declined from 291.8‰ (n = 765) to 111.4‰ (n = 292) in LLIN + Bti arm (P < 0.001). CONCLUSIONS: The combined use of LLINs with Bti significantly reduced the incidence of malaria. The LLINs and Bti duo could be a promising integrated approach for effective vector control of An. gambiae for elimination of malaria.

Ownership and use of insecticide-treated nets in Myanmar: insights from a nationally representative demographic and health survey.

BACKGROUND: Malaria poses a substantial public health threat in Myanmar, indicating the need for rigorous efforts to achieve elimination of the disease nationwide by 2030. The use of insecticide-treated nets (ITNs) forms part of a pivotal strategy for preventing transmission. This study explored the ownership and use of ITNs in Myanmar and identified factors associated with non-use of ITNs. METHODS: Household datasets from the 2015-2016 Myanmar Demographic and Health Survey were utilised, which encompassed all household members except children under the age of five. Descriptive statistics and inferential tests, including simple and multiple logistics regression models and Pearson correlations, were employed for analysis. All analyses, taking the two-stage stratified cluster sampling design into account, used weighting factors and the "svyset" command in STATA. The ownership and use of bed nets were also visualised in QGIS maps. RESULTS: Among the 46,507 participants, 22.3% (95% CI 20.0%, 24.5%) had access to ITNs, with only 15.3% (95% CI 13.7, 17.1%) sleeping under an ITN the night before the survey. Factors associated with the non-use of ITNs included age category (15-34 years-aOR: 1.17, 95% CI 1.01, 1.30; 50+ years-aOR: 1.19, 95% CI 1.06, 1.33), location (delta or lowland-aOR: 5.39, 95% CI 3.94, 7.38; hills-aOR: 1.80, 95% CI 1.20, 2.71; plains-aOR: 3.89, 95% CI 2.51, 6.03), urban residency (aOR: 1.63, 95% CI 1.22, 2.17), and wealth quintile (third-aOR: 1.38, 95% CI 1.08, 1.75; fourth-aOR: 1.65, 95% CI 1.23, 2.23; fifth-aOR: 1.47, 95% CI 1.02, 2.13). A coherent distribution of the ownership and use of ITNs was seen across all states/regions, and a strong correlation existed between the ownership and use of ITNs (r: 0.9795, 95% CI 0.9377, 0.9933, alpha < 0.001). CONCLUSIONS: This study identified relatively low percentages of ITN ownership and use, indicating the need to increase the distribution of ITNs to achieve the target of at least one ITN per every two people. Strengthening the use of ITNs requires targeted health promotion interventions, especially among relatively affluent individuals residing in delta or lowland areas, hills, and plains.

Factors associated with the risk of malaria among children: analysis of 2021 Nigeria Malaria Indicator Survey.

BACKGROUND: Malaria remains a burden globally, with the African region accounting for 94% of the overall disease burden and deaths in 2019. It is the major cause of morbidity and mortality among children in Nigeria. Though different environmental factors have been assessed to influence the distribution and transmission of malaria vectors, there is a shortage of information on how they may influence malaria transmission among under-fives in Nigeria. METHODS: This study was based on the secondary data analysis of the Nigeria Malaria Indicator Survey 2021. The study sample comprised 10,645 women (aged 15-49) who delivered a child in the 2 years preceding the survey. The study was restricted to under-fives. Logistic regression was used to identify factors associated with the risk of malaria. RESULTS: There was a positive association between the risk of malaria and heard/seen malaria messages in the last 6 months (AOR 1.39, 95% CI 1.19-1.62), houses with walls built using rudimentary materials (AOR = 1.38, 95% CI 1.04-1.83), at least 6 children living in the house (AOR 1.22, 95% CI 1.00-1.49), children being 1 or 2 years old was associated with increased odds (AOR 1.89, 95% CI 1.50-2.34 and AOR 1.89, 95% CI 1.52-2.36), children from households with only treated nets (AOR 1.23, 95% CI 1.04-1.46) and those from the North West or South East regions (AOR 1.50, 95% CI 1.10-2.05 and AOR 1.48, 95% CI 1.01-2.16), respectively. All other predictors were not associated with the risk of malaria. CONCLUSION: The factors associated with the risk of malaria in this study included sleeping under treated mosquito nets, the age of the children, residing in the northwest and southeast regions, wall construction material, 6 children and above in the household and hearing/seen malaria messages in the last 6 months. Continuous health education and public health interventions, such as the provision of LLITNs, will reduce the risk of malaria and improve the health and well-being of children under 5 years of age.

Low long-lasting insecticidal net use in malaria elimination areas in Southern Ethiopia: results from community based cross-sectional study.

BACKGROUND: Despite remarkable progress in malaria burden reduction, malaria continues to be a major public health problem globally. Ethiopia has been distributing long-lasting insecticidal nets (LLINs) for free and nationwide distribution was completed in 2016. However, evidence suggests that the utilization of LLINs varies from setting to setting and from time to time due to different factors, and up-to-date evidence is required for LLIN related decision-making. Hence, this study was designed to assess LLIN utilization and its determinants in the Southern Nations, Nationalities, and People's Region (SNNPR) of Ethiopia. METHODS: A community-based cross-sectional study was conducted in Southern Ethiopia in 2019. Using multi-stage sampling, a total of 2466 households were included. The region was stratified based on the annual malaria index as high, moderate, low, and free strata. Cluster sampling was then applied to select households from high, moderate, and low strata. Data on LLIN ownership, utilization and different determinant factors were collected using household questionnaire. SurveyCTO was used to collect data and data was managed using Stata 15. Descriptive statistics and multilevel mixed-effects logistic regression were performed to identify the determinants of utilization of LLINs. Effect measures were reported using adjusted odds ratio (AOR) with 95% CI. RESULTS: From a total of 2466 households, 48.7% of households had at least one LLIN. LLIN adequacy based on family size was 23% while it was15.7% based on universal access and 29.2% based on sleeping space. From 1202 households that possessed LLIN(s), 66.0% of households reported that they slept under LLIN the night preceding the survey. However, when the total population in all surveyed households were considered, only 22.9% of household members slept under LLIN the night preceding the survey. Malaria endemicity, educational status, wealth status, and knowledge about malaria were associated with LLINs utilization. In addition, reasons for non-use included perceived absence of malaria, side effects of LLIN, conditions of LLINs, inconvenient space and low awareness. CONCLUSION: Low LLIN coverage and low utilization were noted. A low level of utilization was associated with malaria endemicity, wealth status and level of awareness. Distribution of LLIN and continuous follow-up with community awareness creation activities are vital to improve coverage and utilization of LLINs, and to ensure the country's malaria elimination goal.

Kenya must wake up to the threat of cryptic Anopheles species and their impact on residual malaria transmission.

Malaria remains a major health problem in Kenya despite the huge efforts put in place to control it. The non-relenting malaria threat has partly been attributed to residual malaria transmission driven by vectors that cannot effectively be controlled by the two popularly applied control methods: long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Reports indicate that residual transmission is widely spread in areas where malaria is endemic. This could mean that the World Health Organization's vision of a world free of malaria remains a mirage as elimination and prevention of re-establishment of malaria are rendered unachievable. Amongst the major contributors to residual malaria transmission are cryptic rare species, species of mosquitoes that are morphologically indistinguishable, but isolated genetically, that have not been the focus of malaria control programs. Recent studies have reported extensive new Anopheles cryptic species believed to be involved in malaria transmission in Kenya. This underscores the need to understand these malaria vector species, their distribution and bionomics and their impact on malaria transmission. This article discusses reports of these cryptic species, their importance to malaria transmission, especially in the arid and semi-arid areas, and what can be done to mitigate the situation.

Physical durability and insecticidal activity of long-lasting insecticidal nets in Cruzeiro do Sul, Brazil.

Vector control is one of the principal strategies used for reducing malaria transmission. Long-lasting insecticidal bed nets (LLINs) are a key tool used to protect populations at risk of malaria, since they provide both physical and chemical barriers to prevent human-vector contact. This study aimed to assess the physical durability and insecticidal efficacy of LLINs distributed in Cruzeiro do Sul (CZS), Brazil, after 4 years of use. A total of 3000 LLINs (PermaNet 2.0) were distributed in high malaria risk areas of CZS in 2007. After 4 years of use, 27 'rectangular' LLINs and 28 'conical' LLINs were randomly selected for analysis. The evaluation of physical integrity was based on counting the number of holes and measuring their size and location on the nets. Insecticidal efficacy was evaluated by cone bioassays, and the amount of residual insecticide remaining on the surface of the LLINs was estimated using a colorimetric method. After 4 years of use, physical damage was highly prevalent on the rectangular LLINs, with a total of 473 holes detected across the 27 nets. The upper portion of the side panels sustained the greatest damage in rectangular LLINs. The overall mosquito mortality by cone bioassay was < 80% in 25/27 rectangular LLINs, with panel A (at the end of the rectangular bednet) presenting the highest mortality (54%). The overall mean insecticide concentration was 0.5 µg/sample, with the bednet roof containing the highest average concentration (0.61 µg/sample). On the conical LLINs, 547 holes were detected, with the bottom areas sustaining the greatest damage. The cone bioassay mortality was < 80% in 26/28 of the conical LLINs. The mean insecticide concentration was 0.3 µg/sample. After 4 years of use, the insecticidal efficacy of the LLINs was diminished to below acceptable thresholds.

An evaluation of LLIN physical integrity and population attitudes towards net use, care and handling during the Magude project in southern Mozambique.

BACKGROUND: The Magude Project assessed the feasibility of eliminating malaria in Magude district, a low transmission setting in southern Mozambique, using a package of interventions, including long-lasting insecticidal nets (LLINs). As the efficacy of LLINs depends in part on their physical integrity, this metric was quantified for Olyset® Nets post mass-distribution, in addition to net use, care and handling practices and other risk factors associated with net physical integrity. METHODS: Nets were collected during a cross-sectional net evaluation, nine months after the Magude project commenced, which was 2 years after the nets were distributed by the National Malaria Control Programme (NMCP). The physical integrity of the nets was assessed by counting and sizing the holes at different positions on each net. A structured questionnaire was administered to assess how the selected net was used and treated (care, wash and repair). Net bio-efficacy was assessed following the standard World Health Organization (WHO) cone bioassay procedures. RESULTS: Out of the 170 Olyset® Nets included in the analysis, 63.5% had been used the night before. The main reason for not using a net was the notion that there were no mosquitoes present. The average number of people using each net was 1.79. Two thirds of the nets had only been washed once or twice since distribution. Most nets (80.9%) were holed and 18% were torn, but none of the risk factors were significantly associated with net integrity, except for presence of mice in the household. Less than half of the participants noticed holes in holed nets, and of those only 38.6% attempted to repair those. None of the six nets that were tested for bio-efficacy passed the WHO threshold of 80% mosquito mortality. CONCLUSION: Overall the majority of Olyset® Nets were in serviceable condition two years post-distribution, but their insecticidal effect may have been lost. This study-together with previous evidence on suboptimal access to and use of LLINs in Magude district-highlights that LLINs as an intervention could have been optimized during the Magude project to achieve maximum intervention impact.

Malaria infection and predictor factors among Chadian nomads' children.

BACKGROUND: In Chad, malaria remains a significant public health concern, particularly among nomadic populations. Geographical factors and the mobility of human populations have shown to be associated with the diversity of Plasmodium species. The study aims to describe the malaria prevalence among nomadic children and to investigate its associated factors. METHODS: A cross-sectional study was conducted in February and October 2021 among nomadic communities in Chad. Blood sample were collected and tested from 187 Arab, Fulani and Dazagada nomadic children aged 3-59 months using malaria rapid diagnostic test (RDT). A structured electronic questionnaire was administered to their parents to collect information about the socio­economic data. Malaria testing results were categorized according to the SD BIOLINE Malaria Ag Pf/Pan RDT procedures. Logistic regression analysis was used to determine key risk factors explaining the prevalence of malaria. STATA version IC 13 was used for statistical analysis. RESULTS: The overall malaria prevalence in nomadic children was 24.60%, with 65.20% being Plasmodium falciparum species and 34.8% mixed species. Boys were twice as likely (COR = 1.83; 95% CI, 0.92-3.62; p = 0.083) to have malaria than girls. Children whose parents used to seek traditional drugs were five times more likely (AOR = 5.59; 95% CI, 1.40-22.30, p = 0.015) to have malaria than children whose parents used to seek health facilities. Children whose parents reported spending the last night under a mosquito net were one-fifth as likely (AOR = 0.17; 95% CI, 0.03-0.90, p = 0.037) to have malaria compared to children whose parents did not used a mosquito net. Furthermore, Daza children were seventeen times (1/0.06) less likely (AOR = 0.06; 95% CI, 0.01-0.70, p = 0.024) to have malaria than Fulani children and children from households piped water as the main source were seven times more likely (AOR = 7.05; 95% CI, 1.69-29.45; p = 0.007) to have malaria than those using surface water. CONCLUSIONS: Malaria remains a significant public health issue in the nomadic communities of Chad. Community education and sensitization programs within nomad communities are recommended to raise awareness about malaria transmission and control methods, particularly among those living in remote rural areas. The National Malaria Control Program (NMCP) should increase both the coverage and use of long-lasting insecticidal nets (LLINs) and seasonal malaria chemoprevention (SMC) in addition to promoting treatment-seeking behaviors in nomadic communities.

Temperature, mosquito feeding status and mosquito density influence the measured bio-efficacy of insecticide-treated nets in cone assays.

BACKGROUND: The WHO cone bioassay is routinely used to evaluate the bioefficacy of insecticide-treated nets (ITNs) for product pre-qualification and confirmation of continued ITN performance during operational monitoring. Despite its standardized nature, variability is often observed between tests. We investigated the influence of temperature in the testing environment, mosquito feeding status and mosquito density on cone bioassay results. METHODS: Cone bioassays were conducted on MAGNet (alphacypermethrin) and Veeralin (alphacypermethrin and piperonyl butoxide (PBO)) ITNs, using laboratory-reared pyrethroid-resistant Anopheles funestus sensu stricto (FUMOZ strain) mosquitoes. Three experiments were conducted using standard cone bioassays following WHO-recommended test parameters, with one variable changed in each bioassay: (i) environmental temperature during exposure: 22-23 °C, 26-27 °C, 29-30 °C and 32-33 °C; (ii) feeding regimen before exposure: sugar starved for 6 h, blood-fed or sugar-fed; and (iii) mosquito density per cone: 5, 10, 15 and 20 mosquitoes. For each test, 15 net samples per treatment arm were tested with four cones per sample (N = 60). Mortality after 24, 48 and 72 h post-exposure to ITNs was recorded. RESULTS: There was a notable influence of temperature, feeding status and mosquito density on An. funestus mortality for both types of ITNs. Mortality at 24 h post-exposure was significantly higher at 32-33 °C than at 26-27 °C for both the MAGNet [19.33% vs 7%; odds ratio (OR): 3.96, 95% confidence interval (CI): 1.99-7.87, P < 0.001] and Veeralin (91% vs 47.33%; OR: 22.20, 95% CI: 11.45-43.05, P < 0.001) ITNs. Mosquito feeding status influenced the observed mortality. Relative to sugar-fed mosquitoes, The MAGNet ITNs induced higher mortality among blood-fed mosquitoes (7% vs 3%; OR: 2.23, 95% CI: 0.94-5.27, P = 0.068) and significantly higher mortality among starved mosquitoes (8% vs 3%, OR: 2.88, 95% CI: 1.25-6.63, P = 0.013); in comparison, the Veeralin ITNs showed significantly lower mortality among blood-fed mosquitoes (43% vs 57%; OR: 0.56, 95% CI: 0.38-0.81, P = 0.002) and no difference for starved mosquitoes (58% vs 57%; OR: 1.05, 95% CI: 0.72-1.51, P = 0.816). Mortality significantly increased with increasing mosquito density for both the MAGNet (e.g. 5 vs 10 mosquitoes: 7% vs 12%; OR: 1.81, 95% CI: 1.03-3.20, P = 0.040) and Veeralin (e.g. 5 vs 10 mosquitoes: 58% vs 71%; OR 2.06, 95% CI: 1.24-3.42, P = 0.005) ITNs. CONCLUSIONS: The results of this study highlight that the testing parameters temperature, feeding status and mosquito density significantly influence the mortality measured in cone bioassays. Careful adherence to testing parameters outlined in WHO ITN testing guidelines will likely improve the repeatability of studies within and between product testing facilities.