Long-lasting insecticidal nets provide protection against malaria for only a single year in Burundi, an African highland setting with marked malaria seasonality

Bortel, Wim Van; Mariën, Joachim; Jacobs, Bart K M; Sinzinkayo, Denis; Sinarinzi, Pierre; Lampaert, Emmanuel; D’hondt, Rob; Mafuko, Jean-Marie; Weggheleire, Anja De; Vogt, Florian; Alexander, Neil; Wint, William; Maes, Peter; Vanlerberghe, Veerle; LeClair, Corey

doi:10.1136/bmjgh-2022-009674

Cited by 6 publications

(2 citation statements)

References 41 publications

(91 reference statements)

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“…While MDCs help improve ownership, population access and use of nets immediately after distribution [2,20,21,22,23,24,25], these endeavours often deteriorate into inefficient systems with nets unevenly distributed amongst households [6]. Furthermore, LLIN indicators frequently drop steeply relatively soon after distribution compromising use, as observed on Bioko [26,27]. Recent momentum is building towards improving efficiency through alternative continuous distribution channels [16,5].…”

Section: Discussionmentioning

confidence: 99%

The challenge of improving long-lasting insecticidal nets coverage on Bioko Island: using data to adapt distribution strategies

García,

Galick,

Smith

et al. 2024

Preprint

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Background: Since 2015, malaria vector control on Bioko Island has relied heavily upon long-lasting insecticidal nets (LLIN) to complement other interventions. Despite significant resources utilised, however, achieving and maintaining high coverage has been elusive. Here, core LLIN indicators were used to assess and redefine distribution strategies. Methods: LLIN indicators were estimated for Bioko Island between 2015 and 2022 using a 1x1 km grid of areas. The way these indicators interacted was used to critically assess coverage targets. Particular attention was paid to spatial heterogeneity and to differences between urban Malabo, the capital, and the rural periphery. Results: LLIN coverage according to all indicators varied substantially across areas, decreased significantly soon after mass distribution campaigns (MDC) and, with few exceptions, remained consistently below the recommended target. Use was strongly correlated with population access, particularly in Malabo. After a change in strategy in Malabo from MDC to fixed distribution points, use-to-access showed significant improvement, indicating those who obtained their nets from these sources were more likely to keep them and use them. Moreover, their use rates were significantly higher than those of whom sourced their nets elsewhere. Conclusions: Striking a better balance between LLIN distribution efficiency and coverage represents a major challenge as LLIN retention and use rates remain low despite high access resulting from MDC. The cost benefit of fixed distribution points in Malabo was deemed significant, providing a viable alternative for guaranteeing access to LLINs to those who use them.

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Section: Discussionmentioning

confidence: 99%

The challenge of improving long-lasting insecticidal nets coverage on Bioko Island: using data to adapt distribution strategies

García,

Galick,

Smith

et al. 2024

Preprint

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“…Studies on the effectiveness of mosquito nets are more prevalent in the African continent, where malaria is also a serious problem [ 3 , 5 , 6 ]. In one study, LLINs distributed in Malawi were evaluated for the presence and absence of holes after 1 to 2 years; the results showed a greater protection for users who had the LLINs without holes [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Long-lasting insecticidal nets (LLINs) for malaria control in an endemic area in Brazil

et al. 2023

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Background Most cases of malaria in Brazil are concentrated in the Amazon region. One of the vector control alternatives recommended by the WHO is the long-lasting insecticidal net (LLIN). This tool is used in the nine federal states of the Brazilian Legal Amazon, where LLINs are essential for reducing vector density and disease transmission as they prevent contact between the mosquito and the individual. The objective of this study was to evaluate the residuality and use of LLIN insecticides in different health regions in a city located in the Brazilian Amazon. Methods A total of 17,027 LLINs were installed in the third, fifth and ninth health regions of the municipality of Porto Velho, Rondonia State, Brazil. The LLINs were of two types: Olyset (permethrin), for around the bed, and Interceptor (alphacypermethrin), for around hammocks. The residuality of 172 LLINs was evaluated using cone bioassays to verify the mortality rate of the mosquito Nyssorhynchus darlingi, over a period of 2 years. Structured questionnaires on the acceptance and use of LLINs were distributed to the participating population (n = 391), covering a total sample of 1147 mosquito nets. The mortality rate was evaluated both in terms of days after LLIN installation and the type of insecticide used. Statistical analyses were based on analysis of variance (ANOVA) and Chi-square and were performed using the SPSS statistical program. Results For the Ny. darlingi mosquito, Interceptor-type LLINs showed residual efficacy, with mortality rates ≥ 80% during the 2-year study period, as determined by the WHO. In contrast, Olyset-type LLINs were associated with a reduction in mortality rates, with 76% and 45% mortality rates in the last two assessments, which occurred during the last 6 months of the study period. Based on the structured questionnaires, the acceptance rate, i.e. percentage of individuals accepting the permanence of the 1147 LLINs sampled, in the three health regions of Porto Velho was 93.8% (of 1076 LLINs). Conclusion The alphacypermethrin-impregnated LLIN was more effective than the LLIN impregnated with permethrin. The results indicate that the correct use of mosquito nets—and consequently the protection of the population—needs to be supported by health promotion actions. These initiatives are considered to be essential for the success of this vector control strategy. New studies that consider the monitoring of the placement of mosquito nets are necessary to provide effective support in the correct use of this methodology. Graphical Abstract

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Evaluating the impact of two next generation long-lasting insecticidal nets on malaria incidence in Uganda: an interrupted time series analysis using routine health facility data

Epstein,

Gonahasa,

Namuganga

et al. 2024

Preprint

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Introduction: Malaria remains a significant public health challenge globally, particularly in sub-Saharan Africa, where progress has stalled in recent years. Long-lasting insecticidal nets (LLINs) are a critical preventive tool against malaria. This study investigated the effectiveness of newer-generation LLINs following a universal coverage campaign in Uganda. Methods: Health facility data collected 36 months prior to LLIN distribution and 24 months after LLIN distribution were utilized from 64 sites that took part in a cluster randomized trial comparing two newer-generation LLINs (pyrethroid-PBO and pyrethroid-pyriproxyfen). Using an interrupted time series approach, we compared observed malaria incidence with counterfactual scenarios if no LLINs were distributed adjusting for precipitation, vegetation, seasonality, and care-seeking behavior. Analyses were also stratified by LLIN type and study-site level estimates of transmission intensity. Results: Overall, malaria incidence decreased from 827 cases per 1,000 person-years in the pre-distribution period to 538 per 1,000 person-years in the post-distribution period. Interrupted time series analyses estimated a 23% reduction in malaria incidence (IRR = 0.77, 95% CI 0.65-0.91) in the first 12 months following distribution relative to what would be expected had no distribution occurred, which was not sustained in the 13-24 month post-distribution period (IRR = 0.97, 95% CI 0.75-1.28). Findings were similar when stratified by LLIN type. In the first 12 months following distribution, LLIN effectiveness was greater in the high transmission sites (IRR = 0.67, 95% CI 0.54-0.86) compared to the medium (IRR = 0.74, 95% CI 0.59-0.92) and low transmission sites (IRR = 0.87, 95% CI 0.56-1.32). Conclusion: This study demonstrated a modest reduction in malaria incidence following the distribution of newer-generation LLINs that was sustained for only 12 months, highlighting the need for improved strategies to maintain net effectiveness. Adjusting the frequency of universal coverage campaigns based on local malaria transmission intensity may enhance control efforts.

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Long-lasting insecticidal nets provide protection against malaria for only a single year in Burundi, an African highland setting with marked malaria seasonality

Cited by 6 publications

References 41 publications

The challenge of improving long-lasting insecticidal nets coverage on Bioko Island: using data to adapt distribution strategies

The challenge of improving long-lasting insecticidal nets coverage on Bioko Island: using data to adapt distribution strategies

Evaluation of Long-lasting insecticidal nets (LLINs) for malaria control in an endemic area in Brazil

Evaluating the impact of two next generation long-lasting insecticidal nets on malaria incidence in Uganda: an interrupted time series analysis using routine health facility data

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