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Bubun N, Anetul E, Koinari M, Johnson PH, Makita LS, Freeman TW, Robinson LJ, Laman M, Karl S. Insufficient duration of insecticidal efficacy of Yahe ® insecticide-treated nets in Papua New Guinea. Malar J 2024; 23:175. [PMID: 38840196 PMCID: PMC11151609 DOI: 10.1186/s12936-024-05005-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Accepted: 05/28/2024] [Indexed: 06/07/2024] Open
Abstract
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.
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Affiliation(s)
- Nakei Bubun
- Papua New Guinea Institute of Medical Research, Madang, Madang, Papua New Guinea
| | - Evodia Anetul
- Papua New Guinea Institute of Medical Research, Madang, Madang, Papua New Guinea
| | - Melanie Koinari
- Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, QLD, Australia
| | - Petrina H Johnson
- Papua New Guinea Institute of Medical Research, Madang, Madang, Papua New Guinea
- Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, QLD, Australia
| | - Leo S Makita
- Papua New Guinea National Department of Health, National Capital District, Port Moresby, Papua New Guinea
| | - Timothy W Freeman
- Rotarians Against Malaria Papua New Guinea, National Capital District, Port Moresby, Papua New Guinea
| | - Leanne J Robinson
- Papua New Guinea Institute of Medical Research, Madang, Madang, Papua New Guinea
- Burnet Institute of Medical Research, Melbourne, VIC, Australia
| | - Moses Laman
- Papua New Guinea Institute of Medical Research, Madang, Madang, Papua New Guinea
| | - Stephan Karl
- Papua New Guinea Institute of Medical Research, Madang, Madang, Papua New Guinea.
- Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, QLD, Australia.
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Effectiveness of long-lasting insecticidal nets in prevention of malaria among individuals visiting health centres in Ziway-Dugda District, Ethiopia: matched case-control study. Malar J 2021; 20:301. [PMID: 34217315 PMCID: PMC8254940 DOI: 10.1186/s12936-021-03833-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Accepted: 06/27/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria 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. METHODS A 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. RESULTS One 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. CONCLUSIONS Sleeping 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.
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Evaluation of the durability of long-lasting insecticidal nets in Guatemala. Malar J 2021; 20:219. [PMID: 33990197 PMCID: PMC8120849 DOI: 10.1186/s12936-021-03722-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 04/03/2021] [Indexed: 12/04/2022] Open
Abstract
Background Insecticide-treated bed nets (ITNs) are widely used for the prevention and control of malaria. In Guatemala, since 2006, ITNs have been distributed free of charge in the highest risk malaria-endemic areas and constitute one of the primary vector control measures in the country. Despite relying on ITNs for almost 15 years, there is a lack of data to inform the timely replacement of ITNs whose effectiveness becomes diminished by routine use. Methods The survivorship, physical integrity, insecticide content and bio-efficacy of ITNs were assessed through cross-sectional surveys conducted at 18, 24 and 32 months after a 2012 distribution of PermaNet® 2.0 in a malaria focus in Guatemala. A working definition of ‘LLIN providing adequate protection’ was developed based on the combination of the previous parameters and usage of the net. A total of 988 ITNs were analysed (290 at 18 months, 349 at 24 months and 349 at 32 months). Results The functional survivorship of bed nets decreased over time, from 92% at 18 months, to 81% at 24 months and 69% at 32 months. Independent of the time of the survey, less than 80% of the bed nets that were still present in the household were reported to have been used the night before. The proportion of bed nets categorized as “in good condition” per World Health Organization (WHO) guidelines of the total hole surface area, diminished from 77% to 18 months to 58% at 32 months. The portion of ITNs with deltamethrin concentration less than 10 mg/m2 increased over time. Among the bed nets for which bioassays were conducted, the percentage that met WHO criteria for efficacy dropped from 90% to 18 months to 52% at 32 months. The proportion of long-lasting insecticidal nets (LLINs) providing adequate protection was 38% at 24 months and 21% at 32 months. Conclusions At 32 months, only one in five of the LLINs distributed in the campaign provided adequate protection in terms of survivorship, physical integrity, bio-efficacy and usage. Efforts to encourage the community to retain, use, and properly care for the LLINs may improve their impact. Durability assessments should be included in future campaigns. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03722-1.
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Karl S, Katusele M, Freeman TW, Moore SJ. Quality Control of Long-Lasting Insecticidal Nets: Are We Neglecting It? Trends Parasitol 2021; 37:610-621. [PMID: 33773912 DOI: 10.1016/j.pt.2021.03.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/25/2021] [Accepted: 03/05/2021] [Indexed: 11/16/2022]
Abstract
Over 2.2 billion long-lasting insecticidal nets (LLINs) for malaria control have been delivered to recipient countries. LLINs are the largest single item in the global malaria control budget. To be eligible for donor-funded procurement and distribution schemes, LLIN products must attain and retain World Health Organization (WHO) prequalification status by passing safety, quality, and efficacy benchmarks. Predelivery inspections further test product quality before distribution. We have shown that, despite these quality-assurance measures, substandard LLINs were distributed in Papua New Guinea (PNG) for at least 6 years (2013-2019). Other countries may have received similar LLINs. Here, we discuss the most important weaknesses of the current LLIN quality-assurance framework that have made this possible.
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Affiliation(s)
- Stephan Karl
- Australian Institute of Tropical Health and Medicine, James Cook University, 1/14-88 McGregor Road, Smithfield, QLD, 4870, Australia; Vector Borne Disease Research Unit, PNG Institute of Medical Research, P.O. Box 378, Madang, 511, Madang Province, Papua New Guinea.
| | - Michelle Katusele
- Vector Borne Disease Research Unit, PNG Institute of Medical Research, P.O. Box 378, Madang, 511, Madang Province, Papua New Guinea
| | - Timothy W Freeman
- Rotarians Against Malaria, P.O. Box 3686, Port Moresby, 121, NCD, Papua New Guinea
| | - Sarah J Moore
- Vector Control Product Testing Unit, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania; Swiss Tropical and Public Health Institute, Vector Biology Unit, Department of Epidemiology and Public Health Socinstrasse, 57, CH-4002 Basel, Switzerland; University of Basel, Petersplatz 1, 4001, Basel, Switzerland
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Ghimire P, Rijal KR, Adhikari N, Thakur GD, Marasini B, Thapa Shrestha U, Banjara MR, Pant SK, Adhikari B, Dumre SP, Singh N, Pigeon O, Chareonviriyaphap T, Chavez I, Ortega L, Hii J. The durability of long-lasting insecticidal nets distributed to the households between 2009 and 2013 in Nepal. Trop Med Health 2020; 48:36. [PMID: 32476984 PMCID: PMC7236445 DOI: 10.1186/s41182-020-00223-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 05/05/2020] [Indexed: 11/10/2022] Open
Abstract
Background Understanding and improving the durability of long-lasting insecticidal nets (LLINs) in the field are critical for planning future implementation strategies including behavioral change for care and maintenance. LLIN distribution at high coverage is considered to be one of the adjunctive transmission reduction strategies in Nepal's Malaria Strategic Plan 2014-2025. The main objective of this study was to assess the durability through assessment of community usage, physical integrity, residual bio-efficacy, and chemical retention in LLINs: Interceptor®, Yorkool®, and PermaNet ®2.0 which were used in Nepal during 2009 through 2013. Methods Assessments were conducted on random samples (n = 440) of LLINs from the eleven districts representing four ecological zones: Terai plain region (Kailali and Kanchanpur districts), outer Terai fluvial ecosystem (Surkhet, Dang, and Rupandhei districts), inner Terai forest ecosystem (Mahhothari, Dhanusa, and Illam districts), and Hills and river valley (Kavrepalanchock and Sindhupalchok districts). For each LLIN, fabric integrity in terms of proportionate hole index (pHI) and residual bio-efficacy were assessed. However, for chemical retention, a representative sample of 44 nets (15 Yorkool®, 10 Permanet®2.0, and 19 Interceptor®) was evaluated. Data were analyzed using descriptive statistics stratified by LLINs brand, districts, and duration of exposure. Results On average, duration of use of LLINs was shortest for the Yorkool® samples, followed by PermaNet® 2.0 and Interceptor® with median ages of 8.9 (IQR = 0.4), 23.8 (IQR = 3.2), and 50.1 (IQR = 3.2) months, respectively. Over 80% of field distributed Yorkool® and PermaNet® 2.0 nets were in good condition (pHI< 25) compared to Interceptor® (66%). Bio-efficacy analysis showed that average mortality rates of Interceptor and Yorkool were below World Health Organization (WHO) optimal effectiveness of ≥ 80% compared to 2-year-old PermaNet 2.0 which attained 80%. Chemical retention analysis was consistent with bio-efficacy results. Conclusion This study shows that distribution of LLINs is effective for malaria control; however, serviceable life of LLINs should be considered in terms of waning residual bio-efficacy that warrants replacement. As an adjunctive malaria control tool, National Malaria Control Program of Nepal can benefit by renewing the distribution of LLINs in an appropriate time frame in addition to utilizing durable and effective LLINs.
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Affiliation(s)
- Prakash Ghimire
- 1Central Department of Microbiology, Tribhuvan University, Kathmandu, Nepal.,World Health Organization Country Office for Nepal, Pulchowk, Lalitpur, Nepal
| | - Komal Raj Rijal
- 1Central Department of Microbiology, Tribhuvan University, Kathmandu, Nepal
| | - Nabaraj Adhikari
- 1Central Department of Microbiology, Tribhuvan University, Kathmandu, Nepal
| | - Garib Das Thakur
- 3Epidemiology and Disease Control Division, Department of Health Services, Ministry of Health and Population, Kathmandu, Nepal
| | - Baburam Marasini
- 3Epidemiology and Disease Control Division, Department of Health Services, Ministry of Health and Population, Kathmandu, Nepal
| | | | - Megha Raj Banjara
- 1Central Department of Microbiology, Tribhuvan University, Kathmandu, Nepal
| | - Shishir Kumar Pant
- 4VectorBorne Disease Research and Training Center, Ministry of Health and Population, Hetauda, Nepal
| | - Bipin Adhikari
- 5Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Shyam Prakash Dumre
- 6Department of Immunogenetics, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
| | - Nihal Singh
- World Health Organization Country Office for Nepal, Pulchowk, Lalitpur, Nepal
| | - Olivier Pigeon
- 7Agriculture and Natural Environment Department, Plant Protection Products and Biocides Physico-chemistry and Residues Unit, Walloon Agricultural Research Centre (CRA-W), Carson Building, Rue du Bordia, 11, B-5030 Gembloux, Belgium
| | | | - Irwin Chavez
- 9Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok, 10400 Thailand
| | - Leonard Ortega
- 10South-East Asia Regional Office, World Health Organization, New Delhi, India.,11Global Malaria Programme World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland
| | - Jeffrey Hii
- 12Malaria Consortium, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok, 10400 Thailand.,13College of Public Health, Medical & Veterinary Sciences, James Cook University, Townville, QLD 4811 Australia
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South A, Lees R, Garrod G, Carson J, Malone D, Hastings I. The role of windows of selection and windows of dominance in the evolution of insecticide resistance in human disease vectors. Evol Appl 2020; 13:738-751. [PMID: 32211064 PMCID: PMC7086049 DOI: 10.1111/eva.12897] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 10/25/2019] [Accepted: 10/28/2019] [Indexed: 01/23/2023] Open
Abstract
Persistent insecticides sprayed onto house walls, and incorporated into insecticide-treated bednets, provide long-acting, cost-effective control of vector-borne diseases such as malaria and leishmaniasis. The high concentrations that occur immediately postdeployment may kill both resistant and susceptible insects. However, insecticide concentration, and therefore killing ability, declines in the months after deployment. As concentrations decline, resistant insects start to survive, while susceptible insects are still killed. The period of time after deployment, within which the mortality of resistant individuals is lower than that of susceptible ones, has been termed the "window of selection" in other contexts. It is recognized as driving resistance in bacteria and malaria parasites, both of which are predominantly haploid. We argue that paying more attention to these mortality differences can help understand the evolution of insecticide resistance. Because insects are diploid, resistance encoded by single genes generates heterozygotes. This gives the potential for a narrower "window of dominance," within the window of selection, where heterozygote mortality is lower than that of susceptible homozygotes. We explore the general properties of windows of selection and dominance in driving resistance. We quantify their likely effect using data from new laboratory experiments and published data from the laboratory and field. These windows can persist months or years after insecticide deployments. Differential mortalities of resistant, susceptible and heterozygous genotypes, after public health deployments, constitute a major challenge to controlling resistance. Greater attention to mortality differences by genotype would inform strategies to reduce the evolution of resistance to existing and new insecticides.
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Affiliation(s)
- Andy South
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
| | - Rosemary Lees
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
| | - Gala Garrod
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
| | | | - David Malone
- Innovative Vector Control Consortium (IVCC)LiverpoolUK
- Present address:
Bill & Melinda Gates FoundationLondonUK
| | - Ian Hastings
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
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Kristan M, Abeku TA, Lines J. Effect of environmental variables and kdr resistance genotype on survival probability and infection rates in Anopheles gambiae (s.s.). Parasit Vectors 2018; 11:560. [PMID: 30367663 PMCID: PMC6204000 DOI: 10.1186/s13071-018-3150-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 10/14/2018] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Environmental factors, especially ambient temperature and relative humidity affect both mosquitoes and malaria parasites. The early part of sporogony is most sensitive and is affected by high temperatures and temperature fluctuation immediately following ingestion of an infectious blood meal. The aim of this study was to explore whether environmental variables such as temperature, together with the presence of the kdr insecticide resistance mutations, have an impact on survival probability and infection rates in wild Anopheles gambiae (s.s.) exposed and unexposed to a pyrethroid insecticide. METHODS Anopheles gambiae (s.s.) were collected as larvae, reared to adults, and fed on blood samples from 42 Plasmodium falciparum-infected local patients at a health facility in mid-western Uganda, then exposed either to nets treated with sub-lethal doses of deltamethrin or to untreated nets. After seven days, surviving mosquitoes were dissected and their midguts examined for oocysts. Prevalence (proportion infected) and intensity of infection (number of oocysts per infected mosquito) were recorded for each group. Mosquito mortality was recorded daily. Temperature and humidity were recorded every 30 minutes throughout the experiments. RESULTS Our findings indicate that apart from the effect of deltamethrin exposure, mean daily temperature during the incubation period, temperature range during the first 24 hours and on day 4 post-infectious feed had a highly significant effect on the risk of infection. Deltamethrin exposure still significantly impaired survival of kdr homozygous mosquitoes, while mean daily temperature and relative humidity during the incubation period independently affected mosquito mortality. Significant differences in survival of resistant genotypes were detected, with the lowest survival recorded in mosquitoes with heterozygote L1014S/L1014F genotype. CONCLUSIONS This study confirmed that the early part of sporogony is most affected by temperature fluctuations, while environmental factors affect mosquito survival. The impact of insecticide resistance on malaria infection and vector survival needs to be assessed separately for mosquitoes with different resistance mechanisms to fully understand its implications for currently available vector control tools and malaria transmission.
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Affiliation(s)
- Mojca Kristan
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK.
| | | | - Jo Lines
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
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Bed nets used to protect against malaria do not last long in a semi-arid area of Ethiopia: a cohort study. Malar J 2018; 17:239. [PMID: 29925371 PMCID: PMC6011348 DOI: 10.1186/s12936-018-2391-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Accepted: 06/14/2018] [Indexed: 11/29/2022] Open
Abstract
Background Long-lasting insecticidal nets (LLINs) are a key tool for malaria prevention and control. Currently, the recommended serviceable life of an LLIN is 3 years under field conditions. However, field studies show considerable variation in LLIN lifespan, from less than 2 years to more than 4 years. This study aimed to determine the attrition, physical integrity, functional survival, and bio-efficacy of LLINs under field conditions in south-central Ethiopia. Methods In October 2014, 7740 LLINs (PermaNet® 2.0) were distributed to 3006 households. Among the distributed LLINs, a cohort study involving 1532 LLINs in 659 households was carried out from October 2014 to November 2016. Data were collected every 6 months by observation, and through interviews with the heads of households. The proportional hole index was used to categorize LLINs as either serviceable or torn. In addition, 120 randomly selected LLINs were tested for bio-efficacy. Results The overall attrition of LLINs was 96% (n = 993) during the study period. The nets’ attrition was mainly due to disposal (64.2%; n = 638). The proportion of LLINs with a hole size 0.5 cm or larger was 79.5% after 24 months. The use of the net on the previous night and having a clean net were associated with a good physical integrity. However, living in a household more than 1 km away from the mosquitoes’ breeding site was associated with poor physical integrity. By the 24th month, only 4% of the nets met the criteria for functional survival. The median functional survival time of the nets was 12 months. A longer functional survival was associated with having a clean net, and shorter survival was associated with living in a household more than 1 km away from the mosquitoes’ breeding site. The PermaNet® 2.0 met the criteria of effective bio-efficacy up to month 24 after distribution. Conclusions The study showed that the median serviceable life of LLINs is only 12 months. However, the bio-efficacy of the LLINs is acceptable for at least 24 months. Therefore, stronger and more efficient LLINs need to be developed for conditions similar to those studied here.
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Randriamaherijaona S, Raharinjatovo J, Boyer S. Durability monitoring of long-lasting insecticidal (mosquito) nets (LLINs) in Madagascar: physical integrity and insecticidal activity. Parasit Vectors 2017; 10:564. [PMID: 29132421 PMCID: PMC5683549 DOI: 10.1186/s13071-017-2419-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 10/03/2017] [Indexed: 11/10/2022] Open
Abstract
Background Long-lasting insecticidal mosquito nets (LLINs) are highly effective for malaria prevention. However, it is also clear that durability monitoring is essential to predict when, post-distribution, a net population, no longer meets minimum WHO standards and needs to be replaced. Following a national distribution campaign in 2013, we tracked two durability indicators, physical integrity and bio-efficacy at six and 12 months post-distribution. While the loss of net integrity during this period was in line with expectations for a one-year net life, bio-efficacy results suggested that nets were losing insecticidal effect faster than expected. The rate of bio-efficacy loss varied significantly between different net brands. Methods We tested 600 randomly selected LLINs, 200 from each of three net brands. Each brand came from different eco-epidemiological zones reflecting the original distribution scheme. Fabric integrity (size and number of holes) was quantified using the proportional hole index (pHI). A subsample of the nets, 134 new nets, 150 at six months and 124 at 12 months, were then tested for bio-efficacy using the World Health Organization (WHO) recommended method. Results Three net types, Netprotect®, Royalsentry® and Yorkool®, were followed. After six months, 54%, 39% and 45%, respectively, showed visible loss of integrity. The median pHI by type was estimated to be one, zero and one respectively. The percentage of damaged nets increased after 12 months such that 83.5%, 74% and 68.5%, had holes. The median pHI for each brand of nets was 47.5, 47 and 23. No significant difference in the estimated pHI at either six or 12 months was observed. There was a statistically significant difference in the proportion of hole size category between the three brands (χ2 = 15.761, df = 4, P = 0.003). In cone bio-assays, mortality of new Yorkool® nets was surprisingly low (48.6%), mortality was 90.2% and 91.3% for Netprotect® and Royalsentry® (F(2, 131) = 81.59, P < 0.0001), respectively. At 12 month use, all tested nets were below the WHO threshold for replacement. Conclusion These findings suggest that there is a need for better net quality control before distribution. More frequent replacement of LLINs is probably not an option programmatically. Regardless of prior approval, LLIN durability monitoring for quality assessment as well as net loss following distribution is necessary to improve malaria control efforts. Electronic supplementary material The online version of this article (10.1186/s13071-017-2419-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sanjiarizaha Randriamaherijaona
- Unité d'Entomologie Médicale, Institut Pasteur de Madagascar, 1274 Avaradoha, 101, Antananarivo, BP, Madagascar. .,Ecole doctorale Sciences de la vie et de l'environnement, Université d'Antananarivo, 101, Antananarivo, Madagascar.
| | - Jacky Raharinjatovo
- Population Services International Madagascar, 7748 Ampefiloha, 101, Antananarivo, BP, Madagascar
| | - Sébastien Boyer
- Medical Entomology Platform, Institute Pasteur of Cambodia, 5 Preah Monivong Blvd (93), Phnom Penh, Cambodia
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Toledo ME, Vanlerberghe V, Rosales JP, Mirabal M, Cabrera P, Fonseca V, Gómez Padrón T, Pérez Menzies M, Montada D, Van der Stuyft P. The additional benefit of residual spraying and insecticide-treated curtains for dengue control over current best practice in Cuba: Evaluation of disease incidence in a cluster randomized trial in a low burden setting with intensive routine control. PLoS Negl Trop Dis 2017; 11:e0006031. [PMID: 29117180 PMCID: PMC5695847 DOI: 10.1371/journal.pntd.0006031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 11/20/2017] [Accepted: 10/11/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Aedes control interventions are considered the cornerstone of dengue control programmes, but there is scarce evidence on their effect on disease. We set-up a cluster randomized controlled trial in Santiago de Cuba to evaluate the entomological and epidemiological effectiveness of periodical intra- and peri-domiciliary residual insecticide (deltamethrin) treatment (RIT) and long lasting insecticide treated curtains (ITC). METHODOLOGY/PRINCIPAL FINDINGS Sixty three clusters (around 250 households each) were randomly allocated to two intervention (RIT and ITC) and one control arm. Routine Aedes control activities (entomological surveillance, source reduction, selective adulticiding, health education) were applied in the whole study area. The outcome measures were clinical dengue case incidence and immature Aedes infestation. Effectiveness of tools was evaluated using a generalized linear regression model with a negative binomial link function. Despite significant reduction in Aedes indices (Rate Ratio (RR) 0.54 (95%CI 0.32-0.89) in the first month after RIT, the effect faded out over time and dengue incidence was not reduced. Overall, in this setting there was no protective effect of RIT or ITC over routine in the 17months intervention period, with for house index RR of 1.16 (95%CI 0.96-1.40) and 1.25 (95%CI 1.03-1.50) and for dengue incidence RR of 1.43 (95%CI 1.08-1.90) and 0.96 (95%CI 0.72-1.28) respectively. The monthly dengue incidence rate (IR) at cluster level was best explained by epidemic periods (Incidence Rate Ratio (IRR) 5.50 (95%CI 4.14-7.31)), the IR in bordering houseblocks (IRR 1.03 (95%CI 1.02-1.04)) and the IR pre-intervention (IRR 1.02 (95%CI 1.00-1.04)). CONCLUSIONS Adding RIT to an intensive routine Aedes control programme has a transient effect on the already moderate low entomological infestation levels, while ITC did not have any effect. For both interventions, we didn't evidence impact on disease incidence. Further studies are needed to evaluate impact in settings with high Aedes infestation and arbovirus case load.
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Affiliation(s)
- Maria Eugenia Toledo
- Department of Epidemiology, Institute of Tropical Medicine “Pedro Kourí”, La Habana, Cuba
| | - Veerle Vanlerberghe
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Julio Popa Rosales
- Provincial Center of Surveillance and Vector Control, Santiago de Cuba, Cuba
| | - Mayelin Mirabal
- Finlay Institute - Center for Vaccines Research and Production, Habana, Cuba
| | - Pedro Cabrera
- Provincial Center of Surveillance and Vector Control, Santiago de Cuba, Cuba
| | - Viviana Fonseca
- Provincial Center of Surveillance and Vector Control, Santiago de Cuba, Cuba
| | | | | | - Domingo Montada
- Department of Epidemiology, Institute of Tropical Medicine “Pedro Kourí”, La Habana, Cuba
| | - Patrick Van der Stuyft
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
- University of Ghent, Ghent, Belgium
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11
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Dieval F, Bouyer J, Fafet JF. An improved extraction method for surface dosage of insecticides on treated textile fabrics. Malar J 2017; 16:14. [PMID: 28049476 PMCID: PMC5209952 DOI: 10.1186/s12936-016-1647-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 12/15/2016] [Indexed: 11/17/2022] Open
Abstract
Background Tens of millions of people live in mosquito-infested regions and controlling mosquito-borne diseases is one of the major interventions aimed at alleviating poverty worldwide. The use of insecticide-treated textiles is one of the most widespread control measures. This includes bed nets, battle clothing or, more generally, textiles use for clothing. These textiles are generally treated with permethrin as active ingredient, which is dosed after extraction of the active molecule present throughout the fabric (measured in mg permethrin/g of fabric) and does not take the effective concentration on the textile surfaces into account. The objective of this study was to propose an improved dosage method that enables measurement of the bioavailable or effective part of active ingredients on the surface of textile treated with insecticides. Methods The proposed method relies on mechanical extraction of active molecules on the surface of the textile in direct contact with either the skin or with the targeted arthropod. Results The results showed that the amount of permethrin measured using the current method is about 200 times higher than the effective surface concentration of the insecticide. In addition, the type of weave or knit influences the effective concentrations of permethrin on the surface of the textile. With the current dosage method, the variation in the concentration of permethrin depending on the type of weave is maximum 8%, whereas with the proposed method, it varies by about 50%. These results were confirmed by bioassays, in which the type of weave significantly affected (p < 10−3) the 100% knockdown time of Anopheles gambiae. Conclusions The bioefficacy of insecticide treatments of fabrics is directly correlated with the effective concentration of insecticide on the textile surface, which can be quantified using the method proposed. This improved method could be used to redefine the limits of actual concentrations of active substance after assessment of the bioefficacy of the treatment and the risk to human health. Further, it enables assessments of the kinetics of insecticide migration in the case of long-lasting insecticide treatment.
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Affiliation(s)
- Florence Dieval
- Laboratoire de Physique Et Mécanique Textile, ENSISA Werner, 11 rue Alfred Werner, 68093, Mulhouse, France.
| | - Jérémy Bouyer
- CIRAD, UMR15 CIRAD-INRA Control of exotic and emerging animal diseases, Campus international de Baillarguet, 34398, Montpellier, France
| | - Jean-François Fafet
- Laboratoire de Physique Et Mécanique Textile, ENSISA Werner, 11 rue Alfred Werner, 68093, Mulhouse, France
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