Insecticide-Treated Nets Can Reduce Malaria Transmission by Mosquitoes Which Feed Outdoors

Insecticide treated nets (ITNs) represent a powerful means for controlling malaria in Africa because the mosquito vectors feed primarily indoors at night. The proportion of human exposure that occurs indoors, when people are asleep and can conveniently use ITNs, is therefore very high. Recent evidence suggests behavioral changes by malaria mosquito populations to avoid contact with ITNs by feeding outdoors in the early evening. We adapt an established mathematical model of mosquito behavior and malaria transmission to illustrate how ITNs can achieve communal suppression of malaria transmission exposure, even where mosquito evade them and personal protection is modest. We also review recent reports from Tanzania to show that conventional mosquito behavior measures can underestimate the potential of ITNs because they ignore the importance of human movements

Reflections on the 2021 World Malaria Report and the future of malaria control

The World Malaria Report, released in December 2021, reflects the unique challenges currently facing the global malaria community. The report showed the devastating toll of malaria, with an estimated 627,000 people losing their lives to the disease in 2020. The improved methodological approach used for calculating cause of death for young children revealed a systematic underestimation of disease burden over the past two decades; and that Africa has an even greater malaria crisis than previously known. While countries were able to prevent the worst-case scenarios, the disruptions due to the COVID-19 pandemic revealed how weak health systems and inadequate financing can limit the capacity of the continent to address the malaria challenge. African countries also face a convergence of biological threats that could redefine malaria control, notably widespread pyrethroid resistance and emerging resistance to artemisinin. Despite these challenges, there is cause for optimism in lessons learned from the COVID-19 pandemic, recent acceleration of cutting edge research and development, and new partnerships that encourage leadership from and ownership by affected countries. This article presents key insights from the 2021 World Malaria Report and reflections on the future trajectories: it was informed by an in-depth discussion with leading malaria experts from the World Health Organization (WHO), the Bill & Melinda Gates Foundation, and the U.S. President's Malaria Initiative (PMI). The discussion took place during the 34th edition of the Ifakara Master Classes, held virtually on December 15th, 2021

Unlocking the human factor to increase effectiveness and sustainability of malaria vector control

BACKGROUND: Progress in the fight against malaria has stalled in recent years, highlighting the importance of new interventions and tailored approaches. A critical factor that must be considered across contexts and interventions is human behaviour. MAIN TEXT: Factors such as acceptance of insecticide-treated nets (ITNs) and indoor residual spraying (IRS), ability and willingness to consistently use and appropriately care for ITNs and refraining from post-spray wall modifications can all impact the success of core vector control interventions. Understanding factors that can drive or inhibit these behaviours can contribute to improved social and behaviour change strategies and in turn, improved outcomes. Likewise, patterns of nighttime activities can reveal specific gaps in protection that cannot be filled by core interventions and inform development and deployment of complementary tools that meet people's needs and preferences. There is an opportunity to increase use of approaches such as human-centred design to engage affected communities more actively in identifying and developing sustainable solutions that meet their needs and lifestyles. Integration of social and behavioural research with entomological and epidemiological evaluations will provide a more complete picture of malaria transmission dynamics and inform improved targeting of context-appropriate interventions. Finally, for gains to be maintained, interventions must be rooted within systems that support long-term success. This includes a movement toward more sustainable vector control solutions, increased decision-making and ownership of research, implementation, and strategy development at the country level, and inclusive approaches that ensure all men, women, boys, and girls are engaged as part of the solution. CONCLUSIONS: No matter how efficacious, a tool will remain ineffective if communities do not engage with it or use it regularly. Entering the next decade in the fight against malaria there is a critical opportunity to elevate the role of social and behaviour change to increase the impact and sustainability of malaria control and elimination efforts. This includes removing social and structural barriers to use of existing tools at all levels, human-centred and inclusive design and implementation of new tools, and movement toward long-term solutions led by affected communities

Behavioural and electrophysiological responses of female Anopheles gambiae mosquitoes to volatiles from a mango bait

Attractive Toxic Sugar Baits (ATSB) are used in a “lure-and-kill” approach for management of the malaria vector Anopheles gambiae, but the active chemicals were previously unknown. Here we collected volatiles from a mango, Mangifera indica, juice bait which is used in ATSBs in Tanzania and tested mosquito responses. In a Y-tube olfactometer, female mosquitoes were attracted to the mango volatiles collected 24–48 h, 48–72 h and 72–96 h after preparing the bait but volatiles collected at 96–120 h were no longer attractive. Volatile analysis revealed emission of 23 compounds in different chemical classes including alcohols, aldehydes, alkanes, benzenoids, monoterpenes, sesquiterpenes and oxygenated terpenes. Coupled GC-electroantennogram (GCEAG) recordings from the antennae of An. gambiae showed robust responses to 4 compounds: humulene, (E)-caryophyllene, terpinolene and myrcene. In olfactometer bioassays, mosquitoes were attracted to humulene and terpinolene. (E)-caryophyllene was marginally attractive while myrcene elicited an avoidance response with female mosquitoes. A blend of humulene, (E)- caryophyllene and terpinolene was highly attractive to females (P < 0.001) when tested against a solvent blank. Furthermore, there was no preference when this synthetic blend was offered as a choice against the natural sample. Our study has identified the key compounds from mango juice baits that attract An. gambiae and this information may help to improve the ATSBs currently used against malaria vectors

Health impact assessment for promoting sustainable development: the HIA4SD project

Health is central to sustainable development, and thus a cross-cutting issue of the SustainableDevelopment Goal (SDG) 2030 agenda. Natural resource extraction projects in Africa haveconsiderable potential to impact on health-related targets of the SDGs. This paper introducesthe rationale and organization of the HIA4SD Project; a 6-year research for development (r4d)project that aims to inform and facilitate a policy dialogue at the national and internationallevel on whether current regulatory approaches to impact assessment in Africa promotesustainable development, placing emphasis on SDG3Good Health and Well-being. TheHIA4SD Project has a focus on large-scale natural resource extraction projects and is imple-mented in four African countries, namely Burkina Faso, Ghana, Mozambique and Tanzania

Mathematical Evaluation of Community Level Impact of Combining Bed Nets and Indoor Residual Spraying upon Malaria Transmission in Areas where the main Vectors are Anopheles Arabiensis Mosquitoes.

Indoor residual insecticide spraying (IRS) and long-lasting insecticide treated nets (LLINs) are commonly used together even though evidence that such combinations confer greater protection against malaria than either method alone is inconsistent. A deterministic model of mosquito life cycle processes was adapted to allow parameterization with results from experimental hut trials of various combinations of untreated nets or LLINs (Olyset, PermaNet 2.0, Icon Life nets) with IRS (pirimiphos methyl, lambda cyhalothrin, DDT), in a setting where vector populations are dominated by Anopheles arabiensis, so that community level impact upon malaria transmission at high coverage could be predicted. Intact untreated nets alone provide equivalent personal protection to all three LLINs. Relative to IRS plus untreated nets, community level protection is slightly higher when Olyset or PermaNet 2.0 nets are added onto IRS with pirimiphos methyl or lambda cyhalothrin but not DDT, and when Icon Life nets supplement any of the IRS insecticides. Adding IRS onto any net modestly enhances communal protection when pirimiphos methyl is sprayed, while spraying lambda cyhalothrin enhances protection for untreated nets but not LLINs. Addition of DDT reduces communal protection when added to LLINs. Where transmission is mediated primarily by An. arabiensis, adding IRS to high LLIN coverage provides only modest incremental benefit (e.g. when an organophosphate like pirimiphos methyl is used), but can be redundant (e.g. when a pyrethroid like lambda cyhalothin is used) or even regressive (e.g. when DDT is used for the IRS). Relative to IRS plus untreated nets, supplementing IRS with LLINs will only modestly improve community protection. Beyond the physical protection that intact nets provide, additional protection against transmission by An. arabiensis conferred by insecticides will be remarkably small, regardless of whether they are delivered as LLINs or IRS. The insecticidal action of LLINs and IRS probably already approaches their absolute limit of potential impact upon this persistent vector so personal protection of nets should be enhanced by improving the physical integrity and durability. Combining LLINs and non-pyrethroid IRS in residual transmission systems may nevertheless be justified as a means to manage insecticide resistance and prevent potential rebound of not only An. arabiensis, but also more potent, vulnerable and historically important species such as Anopheles gambiae and Anopheles funestus

What Africa can do to accelerate and sustain progress against malaria

After a longstanding global presence, malaria is now largely non-existent or suppressed in most parts of the world. Today, cases and deaths are primarily concentrated in sub-Saharan Africa. According to many experts, this persistence on the African continent reflects factors such as resistance to insecticides and drugs as well as insufficient access to essential commodities such as insecticide-treated nets and effective drugs. Crucially, however, this narrative ignores many central weaknesses in the fight against malaria and instead reinforces a narrow, commodity-driven vision of disease control. This paper therefore describes the core challenges hindering malaria programs in Africa and highlights key opportunities to rethink current strategies for sustainable control and elimination. The epidemiology of malaria in Africa presents far greater challenges than elsewhere and requires context-specific initiatives tailored to national and sub-national targets. To sustain progress, African countries must systematically address key weaknesses in its health systems, improve the quality and use of data for surveillance-responses, improve both technical and leadership competencies for malaria control, and gradually reduce overreliance on commodities while expanding multisectoral initiatives such as improved housing and environmental sanitation. They must also leverage increased funding from both domestic and international sources, and support pivotal research and development efforts locally. Effective vaccines and drugs, or other potentially transformative technologies such as genedrive modified mosquitoes, could further accelerate malaria control by complementing current tools. However, our underlying strategies remain insufficient and must be expanded to include more holistic and context-specific approaches critical to achieve and sustain effective malaria control

Evaluation of different deployment strategies for larviciding to control malaria: a simulation study

BACKGROUND: Larviciding against malaria vectors in Africa has been limited to indoor residual spraying and insecticide-treated nets, but is increasingly being considered by some countries as a complementary strategy. However, despite progress towards improved larvicides and new tools for mapping or treating mosquito-breeding sites, little is known about the optimal deployment strategies for larviciding in different transmission and seasonality settings. METHODS: A malaria transmission model, OpenMalaria, was used to simulate varying larviciding strategies and their impact on host-seeking mosquito densities, entomological inoculation rate (EIR) and malaria prevalence. Variations in coverage, duration, frequency, and timing of larviciding were simulated for three transmission intensities and four transmission seasonality profiles. Malaria transmission was assumed to follow rainfall with a lag of one month. Theoretical sub-Saharan African settings with Anopheles gambiae as the dominant vector were chosen to explore impact. Relative reduction compared to no larviciding was predicted for each indicator during the simulated larviciding period. RESULTS: Larviciding immediately reduced the predicted host-seeking mosquito densities and EIRs to a maximum that approached or exceeded the simulated coverage. Reduction in prevalence was delayed by approximately one month. The relative reduction in prevalence was up to four times higher at low than high transmission. Reducing larviciding frequency (i.e., from every 5 to 10 days) resulted in substantial loss in effectiveness (54, 45 and 53% loss of impact for host-seeking mosquito densities, EIR and prevalence, respectively). In seasonal settings the most effective timing of larviciding was during or at the beginning of the rainy season and least impactful during the dry season, assuming larviciding deployment for four months. CONCLUSION: The results highlight the critical role of deployment strategies on the impact of larviciding. Overall, larviciding would be more effective in settings with low and seasonal transmission, and at the beginning and during the peak densities of the target species populations. For maximum impact, implementers should consider the practical ranges of coverage, duration, frequency, and timing of larviciding in their respective contexts. More operational data and improved calibration would enable models to become a practical tool to support malaria control programmes in developing larviciding strategies that account for the diversity of contexts

Knowledge, attitudes and practices of prevention of mother to child transmision of HIV among women in Laroo Division Gulu Municipality, Uganda

This study is exploring the knowledge, attitudes and practices of Prevention of Mother to Child Transmission (PMTCT) of Human Immunodeficiency Virus (HIV) among child bearing women aged between 15- 45 years old in Laroo division in Gulu municipality. The goal of the study was to determine the level of attitude as well as of knowledge and belief about PMTCT and proportion of women practicing it among the child bearing women of Laroo Division. The Cross-sectional and Descriptive study design was applied in multistage sampling method with random selection of a parish followed by random selection of a village within the parish from which a sample of homesteads was randomly selected. From each homesteads, a single respondent was randomly selected and registered in the study. Questionnaires were given to respondents that had consented to take part in the study. A total of 208 respondents were registered and interviewed in a period of February to march 2011. There were 165 (79.3%) of the mothers who had knowledge about various PMTCT methods. Of these 86(52%) heard about PMTCT first from hospital. 50 (30%) knew about exclusive breast feeding, while another 50(30%) use of ART, 45(27%) knew about replacement feedings and only 21(13%) knew of elective caesarean section as method of PMTCT. However the majority of the mothers 159(96.5%) thought that PMTCT was beneficial. Nevertheless some mothers thought that PMTCT causes various counter indications including infertility 17 (10.5%) and abnormalities in children at birth 27 (16.7). Their HIV serostatus also varied. Of the 135(81.7%) screened for HIV 42(31.2%) tested HIV positive and only 27 (64.2%) used contraceptives to prevent pregnancy while they were HIV positive. However of the correspondents who tested positive in their last HIV tests, the majority (83%) had had at least a pregnancy after testing HIV positive of which 6.8% did not practice PMTCT. Our study suggests evidence that Knowledge, attitude and practice of PMTCT among women of reproductive age in Laroo Division in Gulu municipality in Northern Uganda is adequate.Nevertheless with the infection rate of 31.2% among them points out that there is a substantial burden of HIV in the women community