VectorGrid-Africa

The challenge

Mosquitoes transmit a wide range of infections, most notably malaria, but also dengue virus and other rare but potentially dangerous pathogens. Factors such as climate change and changing land use are having a profound impact on the ecology of mosquitoes, affecting their numbers and distribution, with important implications for the spread of these infections.

Currently, limited surveillance data are available for mosquitoes and mosquito-borne diseases in sub-Saharan Africa. Data collection is not standardised, and data are generally not shared to create an overall picture of patterns in the distribution of mosquito populations. Furthermore, there is often limited collaboration between researchers and public health officials, a barrier to the use of research evidence to inform disease control.

The project

The long-term goal of the VectorGrid-Africa project team is to establish a pan-African platform for the collection and analysis of data on disease-transmitting mosquitoes. Through a pilot phase, such a platform is being created in five countries in East and Southern Africa – Kenya, Madagascar, Mozambique, South Africa and Tanzania.

The project is establishing data collection nodes in each country at sites with varying environmental conditions. At each site, mosquitoes will be collected at specific times of the year and subjected to intensive analysis. This will include:

• Genomic analysis and sequencing, to identify the mosquito species, key genetic traits such as insecticide resistance, and genomic shifts occurring over time.
• Detection of malaria parasites and viruses being carried by mosquitoes.
• Characterisation of mosquito traits. 

The project will draw upon innovative new analytical approaches. These include genetic techniques that enable multiple types of information to be gained in a single test, including the species of mosquito being analysed, the source of its last blood meal, and whether it is carrying malaria parasites. 

In addition, a relatively new technology, infrared spectral analysis, will be used to characterise multiple aspects of trapped mosquitoes, including their species, age, infection with pathogens or commensal bacteria, last blood meal, and insecticide resistance. This technology is highly promising as it requires no reagents and can be done with widely available desktop scanners. 

At each node, ten sentinel villages will be selected, with mosquito collection carried out monthly or twice a year. Data will be collected on an anticipated 300,000 mosquitoes during the project. Linked data will be recorded on environmental conditions and climate, using local data sources and satellite data. Some clinical data on key infections such as malaria will be collected from facilities in each country. 

In Tanzania, the project will also pilot a One Health approach. Working with local veterinary officers to gather samples from cattle, the project will generate data on Rift Valley fever virus, a highly dangerous pathogen with the potential to be transmitted from livestock and other animals to humans. 

The data will be integrated to generate mathematical models of mosquito populations and disease transmission. These models will be used to explore the potential impacts of different climate change scenarios and land-use changes. They will reveal possible disease hotspots and enable the evaluation of the impact of different control interventions. 

Impact

The VectorGrid-Africa project is piloting an approach that could provide the basis of a comprehensive surveillance system for disease-transmitting mosquitoes. It will:

• Create a platform for the intensive and standardised characterisation of mosquitoes and the pathogens they are carrying in five African countries.
• Strengthen local capacity to use genomics and other new tools to characterise mosquitoes.
• Provide policymakers with information on current mosquito populations plus tools for modelling potential changes linked to climate trends and land-use changes.
• Enable policymakers to anticipate changes in disease patterns and evaluate possible disease control strategies.

The project will provide tools to enable policymakers in the five countries to anticipate likely shifts in mosquito-transmitted diseases, thereby improving their preparedness to prevent and control disease outbreaks. Furthermore, over the longer term, the project will provide a model to underpin region-wide adoption of mosquito surveillance.