HYDROMAL: Hydro-dynamic drivers of malaria transmission hazard in Africa

Lead Research Organisation: Aberystwyth University
Department Name: IBERS

Abstract

HYDROMAL: Hydro-dynamic drivers of human malaria transmission hazard in Africa. Thomas, Macklin, Smith and Gamarra Summary Malaria is a vector borne disease - we become infected by the bite of an infected mosquito. There is currently great concern that climate change may improve conditions for many disease vectors, such as mosquitoes, and that diseases like malaria will increase. The main burden of this disease falls in Africa, where changes in rainfall and temperature are projected to occur over the next century. While we have a reasonably good understanding, from laboratory studies, of how changed temperature may effect mosquito populations, we have very little on the effect of changed rainfall, which controls the availability of mosquito breeding sites. The distribution of these breeding sites in relation to human hosts is the main driver of local epidemiology, and in many locations across Africa it is likely that changes in precipitation, not temperature, will drive changes in transmission. This is the critical gap our project aims to fill, not by developing new science, but by adding value to existing knowledge by coupling different disciplines. Modern challenges require interdisciplinary thinking, and our project is an example of this. We aim to link well-established tools from geophyscial hydrology with mathematical models of malaria transmission, models that have been around for over 50 years. To quantify this relationship we will spend a year in the field in Tanzania, with a parallel program of hydrology and entomology, working in a large valley with the highest levels of malaria transmission in the world. We will then spend a further year analyzing the data and linking the mathematics. Our idea is that if we can predict where the breeding sites for vector mosquitoes will be at any given time, based on rainfall and terrain, we can estimate the malaria transmission. If we can prove this simple idea works, it will pave the way for future studies linking climate change projections to impact on this disease in Africa. It may also prove useful for health planners: it may prove more effective to target resources in key locations, and it may be that different interventions are more effective in different landscapes.
 
Description Larval source management of the Anopheles mosquitoes that transmit malaria in sub-Saharan Africa is a promising component of integrated malaria control and elimination, but this requires development of a framework to target productive locations. In this project we investigated this through process-based understanding of habitat hydrology and geomorphology.

We conducted the first catchment scale study of fine resolution spatial and temporal variation in Anopheles habitat and productivity in relation to rainfall, hydrology and geomorphology for a high malaria transmission area of Tanzania. Monthly aggregates of rainfall, river stage and water table were not significantly related to the abundance of vector larvae at individual sites. However, these metrics showed strong explanatory power to predict mosquito larval abundances after stratification by water body type, with a clear seasonal trend for each, defined on the basis of its geomorphological setting and origin.
We have therefore discovered that hydrological and geomorphological processes governing the availability and productivity of Anopheles breeding habitat need to be understood at the local scale in order to effectively target larval source interventions. Mapping and monitoring these processes is a well-established practice providing a tractable way forward for developing important malaria management tools, particularly in combination with high-resolution satellite remote sensing.
Exploitation Route We have shown that local geomorphological and hydrological characterisation is required in order to interpret which water bodies are 'turning on or off' for mosquito production. This varies with rainfall so is a dynamic process. Moreover each water body type appears to follow a characterisitic trajectory of suitability thus presenting the potential for predictive mapping - perhaps up to several weeks in advance of peak productivity. Hydrological and meteorological instrumentation of landscapes such as conducted here is not feasible outside test areas. However, high-resolution (time, space) radar remote sensing of water bodies can now be considered (we have previously piloted this with the European Space Agency), now that we understand that the imagery needs to be interpreted in relation to local hydrology and geomorphology. We have shown the salient features can be characterised from high resolution terrain models and archive optical satellite imagery. We are thus working toward near real-time monitoring of the environment and prediction of malaria mosquito production, in order to target local interventions.
Sectors Aerospace, Defence and Marine,Environment,Healthcare
 
Description High resolution malaria incidence mapping is being developed by our Tanzanian partners and other stakeholders for operational use. We demonstrated in our NERC funded stakeholder workshop the potential of adding predictive environmental information to these systems. This research led to an invitation to attend and give a keynote presentation to the Global Health Group at UCSF, who are coordinating world-wide efforts in malaria elimination (Dec 2015). The meeting was attended by academics, funders and industry and provided new opportunities to apply our findings to operational malaria prediction and intervention planning. Our approach has attracted the attention of the Zanzibar Malaria Control Program for use on the island of Zanzibar, where a major elimination campaign is underway - we have worked through the Innovative Vector Control Consortium based at Liverpool University to develop this program which has been funded as a three year award 2018-2021 ( added to Researchfish under further funding ). The approaches to malaria spatial targeting developed in this NERC proposal have been presented to the Roll Back Malaria Initiative in Geneva 2018, which is leading to new collaborations.
Sector Environment,Healthcare
Impact Types Societal,Economic,Policy & public services
 
Title LIS-MAL estimates of hydro-climatic suitability for malaria transmission in Africa (1971-2100) 
Description Estimates of climatic suitability for malaria transmission in Africa over the periods 1971-2005, 2011-2040, 2041-2070 and 2071-2100. Seven climate projections using the high concentration scenario (RCP 8.5) were produced with EC-EARTH3-HR v3.1 by the Swedish Meteorological and Hydrological Institute (described in the Excel workbook). These were used to run the Lisflood hydrological model at 0.5 degree resolution and estimate hydro-climatic suitability for malaria transmission based on the Mordecai temperature ranges and Lisflood-predicted surface water availability. For each time period and each of the seven GCMs (i.e. 28 rasters) a 0.5 degree raster layer of the 'number of suitable months for malaria transmission' over Africa is presented in the form of a Geotiff. An Excel spreadsheet summarises these files in terms of total area in each 1 month category for the Lisflood estimates and the estimated changes in suitability between time periods. The population estimated to live within areas hydro-climatically suitable for malaria transmission is also presented, incorporating both present day estimates and future predictions. These data are broken down by country and summarised in terms of 'population months' for each time period. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL https://archive.researchdata.leeds.ac.uk/715/
 
Description AU-IHI 
Organisation Ifakara Health Institute
Country Tanzania, United Republic of 
Sector Charity/Non Profit 
PI Contribution substantial work from both parties to link NERC HYDROMAL project into other funded research, notably the Bill & Melinda Gates Foundation funded project 'Control of Malaria Vectors by the Auto Dissemination of Insecticides' led by Dr Silas Majambere. Time spent on this collaboration and discussing the NERC project by IHI staff, data, transport, meetings etc estimated at $50,000 in kind.
Collaborator Contribution Meetings and workshops, joint writing publications, provision of data, field logistic support beyond that provided for in NERC award, organisational support in Tanzania (e.g. local finances, HR). Of particular note is the substantial work/advice put in by partners to ensure Ethical and Project approval was granted by Tanzanian authorities.
Impact multi-discplinary: physical geography (hydrology, geomorphology), ecology, molecular biology, public health entomology. doi: 10.1371/journal.pone.0068679
Start Year 2011
 
Description Roll Back Malaria Vector Control Working Group, Annual meeting Geneva 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Third sector organisations
Results and Impact Invited presentation to global working group comprising malaria control policy makers (eg WHO, governments), practitioners (national elimination campaign teams) and industry (chemical, development consultancies). Invited to present state-of-the-art and potential for spatial technology approaches to target areas for interventions by larval source management.
Year(s) Of Engagement Activity 2018
URL https://rollbackmalaria.com/organizational-structure/working-groups/vcwg/