Background
Malaria remains a major contributor to worldwide disease burden and poverty. In the past decade, malaria control efforts have increased tremendously, culminating in appreciable declines in global burden of the disease [
1]. Endemic countries have deployed efficacious vector control using indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) as hallmark interventions, alongside case management with effective treatment using artemisinin-based combination therapy (ACT) guided by definitive diagnosis [
2].
In Malawi, IRS for malaria vector control with Gammexane dates back to 1913 under the Sanitary Board Ordinance and Public Works Departments [
3]. During the 1990s, small-scale IRS programmes were embarked upon by the private sector (Illovo Malawi Sugar Company) [
3]. These efforts provided a model and enthusiasm for operational scale IRS implementation by the National Malaria Control Programme (NMCP). In 2007, with support from the US President’s Malaria Initiative (PMI), the NMCP piloted IRS in one high-transmission district, Nkhotakota, eventually scaling up to cover two full districts [
4]. In 2010, based on the success of the initial pilot, the Government of Malawi/Ministry of Health (GoM/MoH) supported IRS in five additional districts [
4]. The Malaria Strategic Plan (2011–2015), extended to end in 2016, proposes further scaling up of IRS to 15 districts [
5]. However, high levels of pyrethroid and carbamate resistance were detected in
Anopheles funestus in multiple sites across the country [
6]. These findings necessitated a shift to more expensive, short-acting organophosphate insecticides. As a consequence, PMI suspended direct support for IRS in Malawi in 2012 [
4].
The IRS programme aims to reduce malaria-related morbidity, mortality and poverty, and to contribute to the Malawi Growth and Development Strategy (MGDS) and Millennium Development Goals (MDGs) [
5]. The GoM-funded IRS operations have declined to only one district in the 2013–2014 spraying season due to inadequate support by partners precipitated by the emergence and spread of insecticide resistance, lack of committed GoM financial resources and technical flaws [
4]. Clearly, the IRS programme in Malawi is grappling with the challenge of sustaining operational-scale implementation. This paper highlights and discusses the successes and continued challenges, and presents opportunities, as an archetype for other countries to learn from the experience of Malawi.
Discussion
The IVM policy has been adopted and implemented as the main approach to vector control by most WHO member states [
25]. Well-established IVM programmes with adherence to the five key attributes of the approach have demonstrated enhanced impact of interventions and opened a window for leveraging additional resources [
26]. In Malawi, the malaria programme review, undertaken in 2010, informed the development a Malaria Vector Control Strategy (2015–2019) in 2014. The strategy was founded on the principals of IVM and spell out tactics and recommendations for improving vector control in Malawi [
21]. The development process involved engagement of research organizations and implementing partners to: (a) assess the operational impact of pyrethroid resistance; (b) explore the potential use of DDT and other long-lasting insecticide formulations for IRS; and, (c) explore the role of alternative vector control innovations in the context of IVM. The strategy prioritizes: (1) use of IRS with non-pyrethroid and non-carbamate insecticides in highly malaria-endemic areas based on epidemiological (along the lakeshore and lower Shire Valley) and entomological (insecticide resistance) data; (2) where feasible, supplement IRS and LLINs with focal larval source management (LSM), preferably using bio-larvicides, according to WHO guidelines; and, (3) determining the diversity of vectors and establishing rational IRM strategies (rotational or mosaic approaches) [
21].
Compromised management of insecticides in agriculture and in public health can lead to selection of insecticide resistance in disease vectors and undermine vector control [
6]. Consolidating the strategic frameworks for IVM will strengthen the IRS efforts, improve management of insecticides and environmental safeguards, and facilitate management of insecticide resistance. It will enhance intersectoral accountability, leading to responsible actions among a wide range of stakeholders and provide a platform for sustaining and maximizing the impact of IRS in a cost-effective manner [
11]. As such, the NMCP should use and manage pesticides judiciously in the context of IVM. High political obligation to combating communicable diseases exists in Malawi. This is exemplified by the availability of a national health strategic plan and good collaboration with various partners, coupled with the commitment of relevant government ministries to jointly support vector control. To ensure adequate stakeholder participation in the planning, design and deployment of interventions, provision of guidance and technical insight to policymakers, improving IEC/BCC and advocacy are necessary.
Malawi is among the countries with the highest malaria transmission intensity worldwide [
12]. In order to successfully control malaria and move towards elimination, the country needs to learn from the experience of other countries in scaling-up proven high-impact vector control interventions. Using the platform of the IVM strategy, some endemic countries have propped up vector control by placing it high on the political agenda, and are making steady progress towards focalized elimination of malaria [
27]. LLINs and IRS are deployed as main thrust interventions supplemented with LSM in accordance with and strict adherence to a set of eligibility criteria [
28,
29]. Botswana, Eritrea, Namibia, South Africa, and Swaziland have implemented and sustained IRS with consistent national government funding supplemented by partner support [
29,
30]. This has resulted in marked reduction in malaria transmission and these countries are now re-orienting toward malaria elimination [
31,
32]. In Zambia, IVM has facilitated strong partner collaboration and has helped leveraging of additional resources for IRS [
27]. Over the years, IRS operations have been financed by the Global Fund, World Bank, PMI, and recently Malaria Control and Evaluation Programme (MACEPA), alongside Zambian Government funding [
33]. Zambia has strengthened GR by incorporating GIS-based satellite imagery to improve IRS planning, targeting, operations, logistics, advocacy and monitoring, and evaluation [
34]. Namibia and Eritrea have recently developed costed IVM strategies for advocacy and leveraging of resources for evidence-based vector control [
35,
36].
Strong entomological teams at national and local levels are crucial to coordinate routine monitoring of resistance, data analysis and interpretation to inform policy decisions, translate policies and guidance into action at ground level. Zambia, Eritrea and Namibia have developed country-specific IRM plans to prevent development and spread of insecticide resistance and have trained local staff in entomological and resistance monitoring [
31]. Zambia and Zimbabwe have also established strong external linkages with international research institutions to further build local entomological capacity. Namibia has elaborated vector surveillance guidelines to facilitate entomological monitoring by the regional levels and have streamlined reporting tools for DDT [
35]. Both Eritrea and Namibia have been conducting contact bioassays and insecticide resistance monitoring over the years and have standardized their IRS data collection and reporting tools in line with WHO guidance. Strengthening environmental safeguards through collaboration with in-country environmental regulatory bodies is also necessary for efficient use of insecticides including DDT.
Conclusions
IRS is a proven and effective malaria vector intervention if correctly implemented using WHO recommended insecticides. However, the future of the IRS programme in Malawi is uncertain due to limited funding, cost of alternative insecticides and technical resource challenges being experienced in the country. DDT is currently not registered for public health use in Malawi due to environmental concerns and strong opposition from the agricultural sector over potential contamination of crops, mainly tobacco which is the main foreign exchange earner, and the inherent loss of export markets. However, the availability of a long-lasting formulation of pirimiphos-methyl makes the re-introduction of IRS a possibility and may be a useful approach for the management of pyrethroid resistance. While the GoM is prioritizing the execution of its malaria control activities, it remains unknown if IRS will remain a high-priority intervention. Future decisions on whether and where to implement IRS will be guided by the IVM strategy. Therefore, implementing the IVM strategy, advocating for sustainable domestic funding and developing an IRM plan and a vector surveillance guideline will be critical in steering entomologic monitoring and future vector control activities in Malawi.
Authors’ contribution
EC conceived the idea to publish, collected and analysed the data, and drafted the manuscript. JC, SM, DA, PT, and WD reviewed the manuscript; TM, JMG and JG contributed to the drafting of the manuscript and critically reviewed the manuscript. All authors read and approved the final manuscript.