RAFT will focus on the most pressing challenges in vector control for mosquito-borne diseases, especially malaria and Aedes-borne viruses.

In the case of malaria, increased access to insecticidal nets supported by international donors has prevented many millions of child deaths in Africa. But these gains are under threat, and could be lost, because insecticide resistance in mosquitoes threatens to erode the protection provided by nets. The good news: we are now seeing the advent of new products with new active ingredients and new tools with new modes of action. However, insecticide resistance is geographically varied. Moreover, donors currently spend more than USD 0.5 billion per year on these products, and RAFT believes that the value-for-money of this expenditure can be improved. The RPC addresses this in Workstream 1 by combining entomological and genetic research in sub-Saharan Africa with mathematical modelling and economic analysis. We will then develop a decision-support tool to guide the selection and deployment of these new products in a cost-effective manner.

RAFT will also strengthen the capacity of national control programmes to tackle two emerging mosquito vectors: Aedes spp. and Anopheles stephensi. Viruses transmitted by Aedes mosquitoes, such as dengue, Chikungunya and Zika, are another rapidly rising problem around the world. These mosquitoes thrive in man-made breeding sites which have increased due to urban expansion over the last few decades. The very recent expansion of An. stephensi into African cities is an additional urgent concern. Intensified transmission in urban centres that previously had little or no malaria could be a major setback for malaria control in the region. It is estimated that by 2025, more than half the African population will live in cities. In Africa, where malaria (a rural disease) has historically been the main focus, knowledge about the biology and control of urban mosquitoes like Aedes and An. stephensi is especially weak. To address this, Workstream 2 of the RPC will:

• Conduct research in Asia and Africa (on the effects of anthropogenic development processes on the epidemiology of mosquito-borne diseases) and
• Set up exchange visits to harness expertise from other continents (including central America and Asia).

Workstream 1: Current threats

Maintaining effective malaria vector control in Africa

Long-lasting insecticidal nets (LLINs) represent approximately 45% of global spending on malaria control. They are also responsible for around 2/3s of the reduction in malaria burden since 2000; over the last 15 years, improved coverage with effective malaria control (especially LLINs) has prevented more than 6 million deaths in sub-Saharan Africa.

However, these gains are fragile: they will be lost if we fail to sustain coverage with effective vector control. Unfortunately, both sustained coverage and effectiveness are under threat, due to limits on donor funding and the rapid evolution of insecticide resistance in African vectors. Various new and more expensive vector control products are being developed and becoming available, but insecticide resistance in SSA varies greatly from place to place.

Thus, national malaria programme managers are faced with a wide variety of questions about cost-effectiveness and value-for-money in resistance management.

The main task for workstream 1 is therefore to address this question: “Given the resistance situation in a target area, and the prices of the available LLIN products, which is the most cost-effective LLIN for that region?”

Our research plan

1. Generate entomological data from experimental hut trials [image labelled experimental huts] in our partner countries (Cameroon, Côte d’Ivoire and Tanzania)
2. Model the expected performance of each LLIN in a target area [image labelled modelling]
3. Develop an economic analysis of the product choice decision [image labelled economic analysis]

Workstream 2: Future Threats

Anticipating and preparing for other emerging VBD threats

This workstream addresses emerging and future threats, and has two core functions:

1. Horizon scanning – research on emerging issues and trends that threaten to increase the transmission of mosquito-borne diseases and/or undermine vector control
2. Building resilience – working with vector control programmes to enhance core capabilities required to detect and respond to emerging threats, and ensuring timely access to relevant technical resources and know-how.

Why is this important?

We will focus on threats which could arise from ongoing processes of development. Human-made landscapes (rural and urban) occupy an ever-increasing fraction of the land-surface of the planet. Urbanisation is a key trend in many developing economies; by 2025, it is estimated that more than 50% of the population in Africa will lie in cities. Two disease vectors thrive in these urban environments:

Aedes aegypti, the primary vector of arboviral diseases (such as dengue, Zika, chikungunya and yellow fever). Aedes-borne arboviruses are a growing problem around the world, yet control is hampered by a lack of fundamental knowledge on disease burden, vector ecology and effective interventions.

 

Anopheles stephensi, an efficient urban vector of malaria. Originating from South Asia, An. stephensi has been invading cities across sub-Saharan Africa

Workstream 2 will consist of four strands of work

- Strengthening expertise on the control of urban mosquitoes: We will be evaluating the Aedes-borne virus situation in Africa and Asia, preparing for the invasion of Anopheles stephensi in Africa, and strengthening research capacity by organising South-South exchange visits between experts in Central America, Africa and Asia.

- The effect of anthropogenic change on mosquito-borne diseases: We will focus on human development trends most likely to impact the risk of VBDs by creating environments which alter human-vector contact, mosquito survival or reproductive success. These are namely changes in housing, electrification, water storage and irrigation.

- Resilience-preparedness for future threats and response plans: How can national disease control programmes prepare for the future, including the threat of invasive new infections? How can we manage human-made landscapes without creating opportunities and niches for vectors? How can we integrated VBD control into intersectoral discussions and national economic development plans? RAFT will attempt to address these questions.

- Vector control in complex humanitarian emergencies: Complex emergency scenarios require specialised interventions. We review the vector control technologies which are effective against malaria in these situations.