Use Of Long-lasting Insecticidal Nets Research Articles

Coverage, determinants of use and repurposing of long-lasting insecticidal nets two years after a mass distribution in Lihir Islands, Papua New Guinea: a cross-sectional study

BackgroundUniversal coverage with long-lasting insecticidal nets (LLINs) is an essential component of malaria control programmes. Three-yearly mass distribution of LLINs in Papua New Guinea (PNG) has been successful in reducing infection transmission since 2009, but malaria prevalence ramped up from 2015 onwards. Although LLIN universal coverage is mostly achieved during these campaigns, it may not be related with net use over time. Uses given to LLINs and non-compliance of this strategy were evaluated.MethodsA knowledge, attitude and practice (KAP) cross-sectional study was conducted in Lihir Islands, PNG, 2–2.5 years after the last LLIN mass distribution campaign. Data on bed net ownership, use and maintenance behaviour was collected using a household questionnaire administered by trained community volunteers. Logistic regression models were used to identify factors associated with owning at least one LLIN and sleeping under a LLIN the previous night.ResultsAmong 2694 households surveyed, 27.4 % (95 % CI: 25.8–29.2) owned at least one LLIN and 8.7 % (95 % CI: 7.6–9.8) had an adequate LLIN coverage (at least one LLIN for every two people). Out of 13,595 individuals in the surveyed households, 13.6 % (95 % CI: 13.0-–4.2) reported having slept under a LLIN the preceding night. Determinants for sleeping under LLIN included living in a household with adequate LLIN coverage [adjusted OR (aOR) = 5.82 (95 % CI: 3.23–10.49)], household heads knowledge about LLINs [aOR = 16.44 (95 % CI: 8.29–32.58)], and female gender [aOR = 1.92 (95 % CI: 1.53–2.40)] (all p-values < 0.001). LLIN use decreased with older age [aOR = 0.29 (95 % CI: 0.21–0.40) for ≥ 15 year-olds, aOR = 0.38 (95 % CI: 0.27–0.55) for 5–14 year-olds] compared to < 5 year-olds (p-value < 0.001). Knowledge on the use of LLIN was good in 37.0 % of the household heads. Repurposed nets were reported serving as fishing nets (30.4 %), fruits and seedlings protection (26.6 %), covering up food (19.0 %) and bed linen (11.5 %).ConclusionsTwo years after mass distribution, LLIN coverage and use in Lihir Islands is extremely low. Three yearly distribution campaigns may not suffice to maintain an acceptable LLIN coverage unless knowledge on maintenance and use is promoted trough educational campaigns.

Geopolitical zones differentials in intermittent preventive treatment in pregnancy (IPTp) and long lasting insecticidal nets (LLIN) utilization in Nigeria.

BackgroundThe coverage of long lasting insecticidal nets (LLIN) and intermittent preventive treatment of malaria in pregnancy (IPTp) uptake for the prevention of malaria commonly vary by geography. Many sub-Saharan Africa (SSA) countries, including Nigeria are adopting the use of LLIN and IPTp to fight malaria. Albeit, the coverage of these interventions to prevent malaria across geographical divisions have been understudied in many countries. In this study, we aimed to explore the differentials in LLIN and IPTp uptake across Nigerian geopolitical zones.MethodsWe analyzed data from Nigeria Multiple Indicator Cluster Survey (MICS) 2016–17. The outcome variables were IPTp and LLIN uptake among women of childbearing age (15–49 years). A total sample of 24,344 women who had given birth were examined for IPTp use and 36,176 women for LLIN use. Percentages, Chi-square test and multivariable logit models plots were used to examine the geopolitical zones differentials in IPTp and LLIN utilization. Data was analyzed at 5% level of significance.ResultsThe overall prevalence of IPTp was 76.0% in Nigeria. Moreover, there were differences across geopolitical zones: North Central (71.3%), North East (76.9%), North West (78.2%), South East (76.1%), South South (79.7%) and South West (72.4%) respectively. Furthermore, the prevalence of LLIN was 87.7%% in Nigeria. Also, there were differences across geopolitical zones: North Central (89.1%), North East (91.8%), North West (90.0%), South East (77.3%), South South (81.1%) and South West (69.8%) respectively. Women who have access to media use, married, educated and non-poor were more likely to uptake IPTp. On the other hand, rural dwellers and those with media use were more likely to use LLIN. Conversely, married, educated, non-poor and women aged 25–34 and 35+ were less likely to use LLIN.ConclusionThough the utilization of IPTp and LLIN was relatively high, full coverage are yet to be achieved. There was geopolitical zones differentials in the prevalence of IPTp and LLIN in Nigeria. Promoting the utilization of IPTp and LLINs across the six geopolitical zones through intensive health education and widespread mass media campaigns will help to achieve the full scale IPTp and LLIN utilization.

Malaria prevalence and long-lasting insecticidal net use in rural western Uganda: results of a cross-sectional survey conducted in an area of highly variable malaria transmission intensity

BackgroundLong-lasting insecticidal nets (LLINs) remain a cornerstone of malaria control, but strategies to sustain universal coverage and high rates of use are not well-defined. A more complete understanding of context-specific factors, including transmission intensity and access to health facilities, may inform sub-district distribution approaches and tailored messaging campaigns.MethodsA cross-sectional survey of 2190 households was conducted in a single sub-county of western Uganda that experiences highly variable malaria transmission intensity. The survey was carried out approximately 3 years after the most recent mass distribution campaign. At each household, study staff documented reported LLIN use and source among children 2 to 10 years of age and performed a malaria rapid diagnostic test. Elevation and distance to the nearest health facility was estimated for each household. Associations between parasite prevalence and LLIN use were estimated from log binomial regression models with elevation and distance to clinic being the primary variables of interest.ResultsOverall, 6.8% (148 of 2170) of children age 2–10 years of age had a positive RDT result, yielding a weighted estimate of 5.8% (95% confidence interval [CI] 5.4–6.2%). There was substantial variability in the positivity rates among villages, with the highest elevation villages having lower prevalence than lowest-elevation villages (p < .001). Only 64.7% (95% CI 64.0–65.5%) of children were reported to have slept under a LLIN the previous night. Compared to those living < 1 km from a health centre, households at ≥ 2 km were less likely to report the child sleeping under a LLIN (RR 0.86, 95% CI 0.83–0.89, p < .001). Households located farther from a health centre received a higher proportion of LLINs from government distributions compared to households living closer to health centres.ConclusionsLLIN use and sourcing was correlated with household elevation and estimated distance to the nearest health facility. The findings suggest that current facility-based distribution strategies are limited in their reach. More frequent mass distribution campaigns and complementary approaches are likely required to maintain universal LLIN coverage and high rates of use among children in rural Uganda.

Effectiveness of long-lasting insecticidal nets in prevention of malaria among individuals visiting health centres in Ziway-Dugda District, Ethiopia: matched case\u2013control study

BackgroundMalaria is a major health problem in Ethiopia. Sleeping under long-lasting insecticidal nets (LLINs) is its major control strategy. Despite high LLINs use (84%) in Ziway-Dugda District, malaria remained a public health problem, raising concern on its effectiveness. Understanding the effectiveness of malaria control interventions is vital. This study evaluated the effectiveness of LLINs and determinants of malaria in Ziway-Dugda District, Arsi Zone Ethiopia.MethodsA matched case–control study was conducted among 284 study participants (71 cases and 213 controls) in Ziway-Dugda District, Arsi Zone, Ethiopia from March to May, 2017. Three health centers were selected randomly, and enrolled individuals newly diagnosed for malaria proportionally. Cases and controls were individuals testing positive and negative for malaria using rapid diagnostic tests. Each case was matched to three controls using the age of (5 years), gender and village of residence. The information was collected using pre-tested structured questionnaires through face to face interviews and observation. Data were entered into Epi-Info version 3.5, and analysed using Stata version-12. Conditional logistic regression was performed, and odds of LLINs use were compared using matched Adjusted Odds Ratio (AOR), 95% confidence interval (CI) and p-value of < 0.05.ResultsOne hundred twenty-three (61.2%) of the controls and 22 (32.8%) of cases had regularly slept under LLINs in the past two weeks. Using multivariate analysis, sleeping under LLINs for the past two weeks (AOR = 0.23, 95%CI = 0.11–0.45); living in houses sprayed with indoor residual spray (IRS) (AOR = 0.23, 95%CI: 0.10–0.52); and staying late outdoors at night in the past two-weeks (AOR = 2.99, 95%CI = 1.44–6.19) were determinant factors.ConclusionsSleeping under LLINs is effective for malaria prevention in the district. IRS and staying late outdoors at night were determinants of malaria. It is recommended to increase attention on strengthening LLINs use and IRS in the area.

Challenges and opportunities for use of long-lasting insecticidal nets to prevent malaria during overnight travel in Uganda: a qualitative study

BackgroundTravel is a well-recognized risk factor for malaria. Within sub-Saharan Africa, travellers from areas of lower to higher transmission intensity are potentially at high risk of malaria. Long-lasting insecticidal nets (LLINs) are the primary tool for prevention of malaria, and their widespread use has contributed to substantial reductions in malaria burden. However, travellers often fail to use LLINs. To further explore the challenges and opportunities of using LLINs, travellers were interviewed in Uganda.MethodsIn August and September 2019, 20 participants attending outpatient clinics at Naguru General Hospital in Kampala with a history of travel out of Kampala within the previous 60 days were purposively selected. Data were collected through in-depth interviews and analysed thematically using NVivo 12.ResultsOf the 20 participants, 13 were male. Thirteen of the 20 participants tested positive for malaria by microscopy, and 5 reported using of LLINs during travel. The main reasons for travel were to attend social events (weddings, funerals, overnight prayers) and for work. travellers who attended social events reported using LLINs less commonly than those who travelled for work. Challenges to using LLINs during travel included: (1) limited access to LLINs; (2) challenges in planning ahead of travel; (3) lack of space or ability to hang LLINs while travelling; (4) impression that LLINs in lodging places were unhygienic; (5) cultural beliefs discouraging use of LLINs during social events; (6) participation in overnight ceremonies; and (7) doubts about efficacy of LLINs. Positive factors influencing use of LLINs during travel included knowledge regarding malaria prevention and good affordability and availability of LLINs.ConclusionsDespite good traveller knowledge regarding malaria control measures, use of LLINs was limited. Use of LLINs in the prevention of malaria among travellers from low to high transmission settings needs to be prioritized. This calls for increased behaviour change oriented communication to improve traveller preparedness and consideration of use of repellents in situations where LLINs may not be feasible. The Uganda Ministry of Health and Malaria Control Division should use educational messages to increase awareness about the risks of getting malaria during overnight travel through the media. Truck drivers should be sensitized through their companies to use the available space at the back of the trucks for hanging nets and consider using pop-up nets.

Coverage enhancement and community empowerment via commercial availability of the long-lasting nets for malaria in India

Achieving malaria elimination goal in India will require supplemental measures to plug in the gaps in implementation of malaria control programmes. Use of long-lasting insecticide nets is one of the two core interventions for vector control in malaria. The most common distribution channel is free delivery via national malaria control programme of various countries and in India, this is the only channel to provide nets to the masses. Understandably, there are gaps in the optimum coverage of at-risk population due to multiple reasons ranging from population growth to time lag in replacements, emergency conditions like floods and logistical impediments among others. At this juncture, it is crucial for India to explore complementary routes to expand access for nets by its people and one is making them available in private sector at an affordable price. The commercial availability of nets offers several advantages like filling in coverage gaps, overcoming additional requirements by families and financial resources being freed up for poor households. However, there are barriers to the successful operationalization of net commercialization like affordability issues, economic viability for manufacturers, regulatory issues etc. All the so-called barriers can be addressed in a concerted and pragmatic way to make access and availability of nets in private market a reality as that is a need of the hour, if India wants to achieve malaria elimination goal by 2030.

Malaria Infection is High at Transit and Destination Phases Among Seasonal Migrant Workers in Development Corridors of Northwest Ethiopia: A Repeated Cross-Sectional Study.

PurposeMalaria is a leading public health problem in Ethiopia. Every year, thousands of seasonal farm workers travel to farm corridors in Northwest Ethiopia and fall at risk of malaria infection. However, the magnitude of malaria infection and risk factors during harvest time were not well identified. This study aimed at estimating the prevalence and risk factors of malaria infection among seasonal migrant workers in Northwest Ethiopia.MethodsA repeated cross-sectional study was conducted at transit and destination phases in Metema district from September 15, 2018 to October 30, 2019. Data were collected using a structured questionnaire. A capillary blood sample was collected to examine infection with malaria parasite using a microscope. A multivariate logistic regression technique was used to determine risk factors.ResultsThe malaria prevalence at transit and destination phases among migrant workers was 13.5% (95% CI: 12.07–14.93%) and 18.7% (95% CI: 16.40–21.02%), respectively. The combined prevalence was 16.1% (95% CI: 14.67–17.63%). The odds of malaria infection among migrant workers at the destination phase was 1.5 (OR=1.5, 95% CI 1.167–1.846) times higher compared to the transit phase. Education (AOR=8.198; 95% CI: 4.318–15.564), knowledge of antimalarial drugs (AOR=2.4; 95% CI: 1.43–3.95), and use of long-lasting insecticidal nets (AOR=5.0; 95% CI: 3.34–4.43) were significantly associated with malaria infection at migration phases.ConclusionThis study showed that the burden of malaria among seasonal migrant workers was high at transit and destination phases. Malaria prevalence was higher at the destination phase compared to the transit phase. A tailored malaria prevention intervention is needed including awareness creation, screening, treatment, repellent, and prophylaxis at both phases to reduce malaria infections.

Family, social and cultural determinants of long-lasting insecticidal net (LLIN) use in Madagascar: secondary analysis of three qualitative studies focused on children aged 5\u201315\xa0years

BackgroundAlthough it is accepted that long-lasting insecticidal net (LLIN) use is an effective means to prevent malaria, children aged 5 to 15 years do not appear to be sufficiently protected in Madagascar; the malaria prevalence is highest in this age group. The purpose of this research is to summarize recent qualitative studies describing LLIN use among the Malagasy people with a focus on children aged 5–15 years.MethodsQualitative data from three studies on malaria conducted between 2012 and 2016 in 10 districts of Madagascar were analysed. These studies cover all malaria epidemiological profiles and 10 of the 18 existing ethnic groups in Madagascar. A thematic analysis was conducted on the collected data from semi-structured interviews, direct observation data, and informal interviews.ResultsA total of 192 semi-structured interviews were conducted. LLINs are generally perceived positively because they protect the health and well-being of users. However, regional representations of mosquito nets may contribute to LLIN lower use by children over 5 years of age including the association between married status and LLIN use, which leads to the refusal of unmarried young men to sleep under LLINs; the custom of covering the dead with a mosquito net, which leads to fear of LLIN use; and taboos governing sleeping spaces for siblings of opposite sexes, which leads to LLIN shortages in households. Children under 5 years of age are known to be the most vulnerable age group for acquiring malaria and, therefore, are prioritized for LLIN use when there are limited supplies in households. In contrast, children over 5 years of age, who are perceived to be at less risk for malaria, often sleep without LLINs.ConclusionsPerceptions, social practices and regional beliefs regarding LLINs and vulnerability to malaria contribute to the nonuse of LLINs among children over 5 years of age in Madagascar. Modifying LLIN policies to account for these factors may increase LLIN use in this age group and reduce disease burden.

Improvement of Indoor Residual Spraying and Long\u2010Lasting Insecticidal Net services through structured monitoring and supervision as part of the Malaria Elimination Demonstration Project in Mandla, Madhya Pradesh

BackgroundThe Government of Madhya Pradesh employed Indoor Residual Spraying (IRS) with alpha-cypermethrin synthetic pyrethroids in sub-centres with Annual Parasite Incidence (API) from 2 to 4.99. In sub-centres with API more than 5, Long-Lasting Insecticidal Nets (LLINs) were distributed. At the request of the State Government, the Malaria Elimination Demonstration Project (MEDP) staff observed and provided support to both IRS and LLINs campaigns. In the year 2017, the study team monitored only the IRS campaigns, however, in the year 2018, the supportive supervision was provided to the IRS campaign teams along with post-distribution monitoring of the LLINs.MethodsThe study was carried out during IRS spraying using a pre-tested, closed-ended monitoring checklist which consisted of two parts- observations of spraying team and observation of sprayed houses. For LLINs, a sample of the households that received the bed nets was taken for the study. For IRS, the spraying teams were monitored for quality and technique for a total of 159 times in 2017 and 183 times in the year 2018, respectively. For post spraying observations, a total of 1261 and 1791 households were observed in the years 2017 and 2018, respectively. The use of LLINs was observed in 5 % of the households in 2018 and 2020, which is about 2,000 houses in each survey where each house received about 2.5 LLINs per household. The results of surveys were compared to assess impact of supportive supervision and monitoring.ResultsSignificant improvement was noted after supportive supervision in year 2018 in various aspects of spraying. Preparedness of spraying, such as advance information to villagers, presence of equipment and records improved by up to 70 %. The methodology of spraying preparation improved from 50 to 90 %, spraying technique improved from 54 to 80 %, and proper use equipment during spraying improved from 51 to 92 %. After eight months post distribution of the LLINs in 2019, improvement was seen in regular usage of LLINs by 28 %. It was found that on-spot demonstrations during distribution and carrying of LLINs when sleeping outside homes increased by 56 %. Results of IEC campaigns revealed the reduction in adverse effects by 64 % and increase in awareness by 97 %.ConclusionsEffective supervision improved the quality of IRS and usage of LLINs in the study area. Based on these results, continued training and monitoring of staff that is deployed to spraying houses and distribute bed nets was suggested. The study also revealed that proper IEC/BCC drives help increase community acceptance of vector control measures and their rational usage.

Ownership and Utilisation of Long-Lasting Insecticidal Nets in Tiko Health District, Southwest Region, Cameroon: A Cross-Sectional Study.

Introduction Malaria is and remains a serious health concern in Africa. In Cameroon, where malaria is endemic and a major public health problem, the major control measure put in place is the use of long-lasting insecticidal nets (LLINs). In the Tiko Health District (THD), the challenges have been to assess and to evaluate the ownership and utilisation of LLINs. This study sought to assess the ownership and utilisation rates of LLINs in the THD. Methodology. A cross-sectional survey involving 418 households was conducted in four health areas in the THD. A structured questionnaire was used to collect data on LLIN ownership and utilisation as well as sociodemographic characteristics. Results The ownership of at least one LLIN per household, coverage, and accessibility were, respectively, 89%, 56.2%, and 66.3%, while installing LLINs on all beds in the household, sleeping under LLINs the previous night (SULPN), and universal utilisation were 72%, 24.9%, and 14.1%, respectively. Factors significantly associated with the ownership of at least one LLIN per household were respondent's age and gender. Heat (21.1%) and forgetfulness (6.5%) were the main reasons postulated for irregular utilisation of LLINs. Conclusion The ownership LLINs failed to guarantee utilisation and definitely effective control of malaria in the THD, as expected. Continuous and appropriate use of LLINs is indispensable, in addition to periodic sanitation, booster campaigns of LLIN distribution, and evaluation research for effective prevention and control of malaria.

Quantifying and characterizing hourly human exposure to malaria vectors bites to address residual malaria transmission during dry and rainy seasons in rural Southwest Burkina Faso

BackgroundTo sustain the efficacy of malaria vector control, the World Health Organization (WHO) recommends the combination of effective tools. Before designing and implementing additional strategies in any setting, it is critical to monitor or predict when and where transmission occurs. However, to date, very few studies have quantified the behavioural interactions between humans and Anopheles vectors in Africa. Here, we characterized residual transmission in a rural area of Burkina Faso where long lasting insecticidal nets (LLIN) are widely used.MethodsWe analysed data on both human and malaria vectors behaviours from 27 villages to measure hourly human exposure to vector bites in dry and rainy seasons using a mathematical model. We estimated the protective efficacy of LLINs and characterised where (indoors vs. outdoors) and when both LLIN users and non-users were exposed to vector bites.ResultsThe percentage of the population who declared sleeping under a LLIN the previous night was very high regardless of the season, with an average LLIN use ranging from 92.43 to 99.89%. The use of LLIN provided > 80% protection against exposure to vector bites. The proportion of exposure for LLIN users was 29–57% after 05:00 and 0.05–12% before 20:00. More than 80% of exposure occurred indoors for LLIN users and the estimate reached 90% for children under 5 years old in the dry cold season.ConclusionsLLINs are predicted to provide considerable protection against exposure to malaria vector bites in the rural area of Diébougou. Nevertheless, LLIN users are still exposed to vector bites which occurred mostly indoors in late morning. Therefore, complementary strategies targeting indoor biting vectors in combination with LLIN are expected to be the most efficient to control residual malaria transmission in this area.

Community Knowledge, Attitude and Practices on Malaria Vector Control Strategies in Lagos State, South-West Nigeria.

Malaria is a leading public health challenge causing mortality and morbidity in sub-Saharan Africa. Prominent malaria vector control methods employed in sub-Saharan Africa include Long Lasting Insecticide Nets (LLINs) and Indoor Residual spraying (IRS). This study investigated knowledge, attitude and practices (KAP) of malaria vector control methods in Lagos, South-West Nigeria. Structured questionnaires were employed for the cross-sectional survey which was carried out between May and August 2018. Multi-stage sampling technique was used to select Lagos Mainland, Kosofe, and Ojo local government areas (LGAs). Five hundred and twenty questionnaires were used for the study. Data were analyzed for descriptive statistics, whereas χ 2 was used to determine influence of respondents' LGA, level of education and type of dwelling on respondents' attitude and practice. Respondents' LGAs have no significant impact on attitude and practice to malaria vector control methods. However, 'level of education' as well as 'type of dwelling structure' impacted significantly on some practices and attitude. Basically, IRS is the major tool employed in malaria vector control, but sometimes it is used in combination with other methods. A good number of residents also use LLINs. 'Choice of method' employed is mainly based on the effectiveness of method. General perception about LLINs and IRS is that they are effective, cheap and safer. Considering the widespread use of IRS and LLINs for malaria vector control in Lagos, implementation of malaria control programs should consider KAP to these two strategies.

Performance of pirimiphos-methyl based Indoor Residual Spraying on entomological parameters of malaria transmission in the pyrethroid resistance region of Koulikoro, Mali

Malaria vector control in Mali relies heavily on the use of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) in selected districts. As part of strengthening vector control strategies in Koulikoro district, the National Malaria Control Programme (NMCP) through the support from the US President's Malaria Initiative (PMI) has strategically driven the implementation of IRS, with the LLINs coverage also rising from 93.3% and 98.2%. Due to the increased reports of vector resistance to both pyrethroid and carbamates, there was a campaign for the use of pirimiphos-methyl, an organophosphate at Koulikoro between 2015 and 2016. In this study, the effect of IRS on malaria transmission was assessed, by comparing some key entomological indices between Koulikoro, where IRS was implemented and its neighboring district, Banamba that has never received IRS as vector control intervention. The study was conducted in two villages of each district (Koulikoro and Banamba). Pyrethrum spray catches and entry window trapping were used to collect mosquitoes on a monthly basis. WHO tube tests were carried out to assess mosquito susceptibility to insecticides. Mosquitoes were identified to species level by PCR and their infection to P. falciparum was detected by Enzyme Linked-Immuno-Sorbent Assay (ELISA). Of the 527 specimens identified, An. coluzzii was the most frequent species (95%) followed by An. gambiae (4%) and An. arabiensis (1%). Its density was rainfall dependent in the no-IRS area, and almost independent in the IRS area. The infection rate (IR) in the no-IRS area was 0.96%, while it was null in the IRS area. In the no-IRS area, the entomological inoculation rate (EIR) was 0.21 infective bites /person month with a peak in September. High resistance to pyrethroids and carbamates and susceptibility to organophosphates was observed at all sites. The introduction of pirimiphos-methyl based IRS for vector control resulted in a significant decrease in malaria transmission. An. gambiae s.l., the main malaria vector in the area, was resistant to pyrethroids and carbamates but remained susceptible to the organophosphate pirimiphos-methyl.

Insights into factors sustaining persistence of high malaria transmission in forested areas of sub-Saharan Africa: the case of Mvoua, South Cameroon

BackgroundIn Mvoua, a village situated in a forested area of Cameroon, recent studies have reported high prevalence of Plasmodium falciparum infection among the population. In order to understand factors that can sustain such a high malaria transmission, we investigated the biology of Anopheles vectors and its susceptibility to insecticides, as well as long-lasting insecticidal net (LLIN) coverage, use and bio-efficacy.MethodsA longitudinal entomological survey was conducted from July 2018 to April 2019. Adult mosquitoes were collected using the human landing catch (HLC) method and identified using morphological and molecular techniques. Anopheles gambiae (s.l.) larvae were sampled from several stagnant water pools throughout the village and reared to generate F1 adults. The presence of P. falciparum circumsporozoite antigen was detected in the heads and thoraces of mosquitoes collected as adults using an enzyme-linked immunosorbent assay. The insecticide susceptibility status of the local An. gambiae (s.l.) F1 population to the pyrethroid insecticides deltamethrin 0.5% and permethrin 0.75% was determined using World Health Organization-tube bioassays, while the frequency of the knockdown resistance (kdr) mutation was determined by PCR. Coverage, use and physical integrity of LLINs were assessed in households, then cone assays were used to test for their bio-efficacy on both the reference insecticide-susceptible Kisumu strain and on field F1 An. gambiae (s.l.)ResultsIn total, 110 Anopheles mosquitoes were collected, of which 59.1% were identified as Anopheles funestus (s.l.), 38.18% as An. gambiae (s.l.) and 2.72% as An. ziemanii. Anopheles funestus was the most abundant species except in the long rainy season, when An. gambiae (s.l.) predominated (65.8%). In the dry seasons, vectors were principally endophagous (76% of those collected indoors) while they tended to be exophagous (66% of those collected outdoors) in rainy seasons. High Plasmodium infection was observed in An. gambiae (s.l.) and An. funestus, with a circumsporozoitic rate of 14.29 and 10.77%, respectively. Anopheles gambiae (s.l.) was highly resistant to pyrethroid insecticides (mortality rates: 32% for permethrin and 5% for deltamethrin) and harbored the kdr-L1014F mutation at a high frequency (89.74%). Of the 80 households surveyed, only 47.69% had achieved universal coverage with LLNs. Around 70% of the LLINs sampled were in poor physical condition, with a proportionate hole index > 300. Of the ten LLNs tested, eight were effective against the An. gambiae reference insecticide-susceptible Kisumu strain, showing mortality rate of > 80%, while none of these LLINs were efficient against local An. gamabie (s.l.) populations (mortality rates < 11.5%).ConclusionA combination of elevated P. falciparum infection in Anopheles vector populations, insufficient coverage and loss of effectiveness of LLINs due to physical degradation, as well as high resistance to pyrethroid insecticides is responsible for the persistence of high malaria transmission in forested rural area of Mvoua, Cameroon.Graphical

Operational Evaluation of the Effectiveness of Long-lasting Insecticidal Nets on Human-Vector Contact in an African Urban Malaria Context

BackgroundMalaria is still a major public health concern in Côte d’Ivoire despite mass distribution of long-lasting insecticidal nets (LLINs) as a key preventive strategy. This study intended to evaluate the operational effectiveness of LLINs on the level of human-vector contact using 1 antibody-based biomarker of exposure to Anopheles in urban areas.MethodsThis cross-sectional study collected socio-demographic data and use of LLINs from 9 neighborhoods in the city of Bouaké (Côte d’Ivoire). Dry blood spots performed in children aged >6 months and adults were used to evaluate immunoglobulin G (IgG) responses to the Anopheles gSG6-P1 salivary peptide.ResultsIgG response levels to the salivary peptide were significantly lower in individuals who declared having “always” (n = 270) slept under an LLIN compared with those who had “often” (n = 2087) and “never” (n = 88) slept under an LLIN (P < .0001). IgG response levels to gSG6-P1 between those who declared having “always” and “not always” slept under an LLIN varied according to neighborhood, socio-professional category, and age group.ConclusionsThe human IgG level to this gSG6-P1 salivary peptide could be a useful tool to evaluate the actual effectiveness of LLINs and help design behavioral change interventions that are crucial for sustaining universal coverage.

Assessing the impact of low-technology emanators alongside long-lasting insecticidal nets to control malaria.

Malaria control in sub-Saharan Africa relies on the widespread use of long-lasting insecticidal nets (LLINs) or the indoor residual spraying of insecticide. Disease transmission may be maintained even when these indoor interventions are universally used as some mosquitoes will bite in the early morning and evening when people are outside. As countries seek to eliminate malaria, they can target outdoor biting using new vector control tools such as spatial repellent emanators, which emit airborne insecticide to form a protective area around the user. Field data are used to incorporate a low-technology emanator into a mathematical model of malaria transmission to predict its public health impact across a range of scenarios. Targeting outdoor biting by repeatedly distributing emanators alongside LLINs increases the chance of elimination, but the additional benefit depends on the level of anthropophagy in the local mosquito population, emanator effectiveness and the pre-intervention proportion of mosquitoes biting outdoors. High proportions of pyrethroid-resistant mosquitoes diminish LLIN impact because of reduced mosquito mortality. When mosquitoes are highly anthropophagic, this reduced mortality leads to more outdoor biting and a reduced additional benefit of emanators, even if emanators are assumed to retain their effectiveness in the presence of pyrethroid resistance. Different target product profiles are examined, which show the extra epidemiological benefits of spatial repellents that induce mosquito mortality.This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases’.

Assessing the Effectiveness of Impregnated Mosquito Nets, 36 Months after Their Distribution in the South of Cameroon

Mosquito control in Cameroon relies largely on the proper use of Long-Lasting Insecticidal Nets (LLINs). It is necessary to monitor their effectiveness in order to propose corrective measures to improve the strategy. The aim of this work was to determine the physical integrity and effectiveness of LLINs (Interceptor brand) on Anopheles gambiae s.l. populations in two urban and rural areas of the Ayos health district. The level of LLIN coverage and use was assessed through a population survey. The physical integrity of LLINs was assessed by measuring the holes according to the WHO method. Bio-efficacy testing of ITNs was carried out according to the cone test protocol using 2-5-day-old, non-blood fed Anopheles gambiae s.l. females from the natural field strain and the reference susceptible strain. Household LLIN coverage rates in urban and rural areas were 55.50% and 66.94%, respectively. On the other hand, the rates of use were 78.01% and 75.22% in urban and rural areas respectively. The proportion of nets that had lost their physical integrity after 36 months of use was 47.00% and 59.63% in urban and rural areas respectively. The size of holes ranged from 0.5 to 25 cm. Alphacypermethrin was found to be ineffective against both strains of Anopheles gambiae s.l. tested. Knockdown rates ranged from 8.5% to 73% for the reference susceptible strain and less than 2.5% for the natural field strain. Mortality rates for the natural strain of Anopheles gambiae s.l. ranged from 0% to 2.5% while they were between 29% and 70% for the susceptible strain. The results show a decrease in the effectiveness of LLINs against the mosquitoes tested. This may be due to the lower than expected WHO possession and use rates of LLINs, their relatively high degree of wear and tear, and the resistance of the vectors to alphacypermethrin.

Coverage outcomes (effects), costs, cost-effectiveness, and equity of two combinations of long-lasting insecticidal net (LLIN) distribution channels in Kenya: a two-arm study under operational conditions

BackgroundMalaria-endemic countries distribute long-lasting insecticidal nets (LLINs) through combined channels with ambitious, universal coverage (UC) targets. Kenya has used eight channels with variable results. To inform national decision-makers, this two-arm study compares coverage (effects), costs, cost-effectiveness, and equity of two combinations of LLIN distribution channels in Kenya.MethodsTwo combinations of five delivery channels were compared as ‘intervention’ and ‘control’ arms. The intervention arm comprised four channels: community health volunteer (CHV), antenatal and child health clinics (ANCC), social marketing (SM) and commercial outlets (CO). The control arm consisted of the intervention arm channels except mass campaign (MC) replaced CHV. Primary analysis used random sample household survey data, service-provider costs, and voucher or LLIN distribution data to compare between-arm effects, costs, cost-effectiveness, and equity. Secondary analyses compared costs and equity by channel.ResultsThe multiple distribution channels used in both arms of the study achieved high LLIN ownership and use. The intervention arm had significantly lower reported LLIN use the night before the survey (84·8% [95% CI 83·0–86·4%] versus 89·2% [95% CI 87·8–90·5%], p < 0·0001), higher unit costs ($10·56 versus $7·17), was less cost-effective ($86·44, 95% range $75·77–$102·77 versus $69·20, 95% range $63·66–$77·23) and more inequitable (Concentration index [C.Ind] = 0·076 [95% CI 0·057 to 0·095 versus C.Ind = 0.049 [95% CI 0·030 to 0·067]) than the control arm. Unit cost per LLIN distributed was lowest for MC ($3·10) followed by CHV ($10·81) with both channels being moderately inequitable in favour of least-poor households.ConclusionIn line with best practices, the multiple distribution channel model achieved high LLIN ownership and use in this Kenyan study setting. The control-arm combination, which included MC, was the most cost-effective way to increase UC at household level. Mass campaigns, combined with continuous distribution channels, are an effective and cost-effective way to achieve UC in Kenya. The findings are relevant to other countries and donors seeking to optimise LLIN distribution.Trial registrationThe assignment of the intervention was not at the discretion of the investigators; therefore, this study did not require registration.

Use of long-lasting insecticidal nets among women attending antenatal clinic at a tertiary hospital in Bayelsa State, Nigeria 2019

BackgroundMalaria in pregnancy remains a major contributor to maternal and infant morbidity and mortality despite scale up in interventions. Its prevention is one of the major interventions in reducing maternal and infant morbidity and mortality. The ownership, utilization and predictors of use of long-lasting insecticide-treated nets (LLINs) for malaria prevention among women attending antenatal clinic (ANC) at a tertiary hospital in Bayelsa State Nigeria was assessed.MethodsA cross-sectional study of 297 women recruited through systematic sampling was carried out. Information on sociodemographic characteristics, ownership, source and utilization of LLINs, were collected with a pre-tested structured interviewer-administered questionnaire. The relationship between use of LLIN and sociodemographic characteristics was examined using chi square and logistic regression at 5% level of significance.ResultsThe mean age of respondents was 28.8 ± 2.6 years. Most (59.2%) had tertiary education and were mainly (88.2%) urban dwellers. Two hundred and fifty (84.2%) owned LLINs, and 196 (78%) used LLIN the night prior to the interview. Almost half of the respondents purchased their LLINs. Those who purchased LLINs were 3 times more likely to have used it (OR: 3.13, 95% CI 1.62–6.04) compared to those that got it free. Those who were gainfully employed (OR: 3.16, 95% CI 1.59–6.29) and those who earned above the minimum wage (OR: 2.88, 95% CI 1.45–5.72) were 3 times more likely to have used LLIN in their index pregnancy.ConclusionThe use of LLIN as a preventive measure against malaria was relatively high among the participants in this study, though still below national target. The major factors determining the use of LLIN among these women were purchase of LLINs and being gainfully employed. It was recommended that efforts should be made to enforce the policy of free LLINs at ANC registration at the tertiary hospitals, as this would further drive up ownership and utilization rates.

A preliminary study on designing a cluster randomized control trial of two new mosquito nets to prevent malaria parasite infection

BackgroundAlthough long-lasting insecticidal nets (LLINs) are the most effective tool for preventing malaria parasite transmission, the nets have some limitations. For example, the increase of LLIN use has induced the rapid expansion of mosquito insecticide resistance. More than two persons often share one net, which increases the infection risk. To overcome these problems, two new mosquito nets were developed, one incorporating piperonyl butoxide and another covering ceilings and open eaves. We designed a cluster randomized controlled trial (cRCT) to evaluate these nets based on the information provided in the present preliminary study.ResultsNearly 75% of the anopheline population in the study area in western Kenya was Anopheles gambiae s. l., and the remaining was Anopheles funestus s. l. More female anophelines were recorded in the western part of the study area. The number of anophelines increased with rainfall. We planned to have 80% power to detect a 50% reduction in female anophelines between the control group and each intervention group. The between-cluster coefficient of variance was 0.192. As the number of clusters was limited to 4 due to the size of the study area, the estimated cluster size was 7 spray catches with an alpha of 0.05. Of 1619 children tested, 626 (48%) were Plasmodium falciparum positive using a rapid diagnostic test (RDT). The prevalence was higher in the northwestern part of the study area. The number of children who slept under bed nets was 929 (71%). The P. falciparum RDT-positive prevalence (RDTpfPR) of net users was 45%, and that of non-users was 55% (OR 0.73; 95% CI 0.56, 0.95). Using 45% RDTpfPR of net users, we expected each intervention to reduce prevalence by 50%. The intracluster correlation coefficient was 0.053. With 80% power and an alpha of 0.05, the estimated cluster size was 116 children. Based on the distribution of children, we modified the boundaries of the clusters and established 300-m buffer zones along the boundaries to minimize a spillover effect.ConclusionsThe cRCT study design is feasible. As the number of clusters is limited, we will apply a two-stage procedure with the baseline data to evaluate each intervention.