The earth is continually orbited and observed by a multitude of satellites. Popular films portray them as watching our every move and sniffing out arch villains from on high. Reality is however far less sinister, as many of these satellites are actually employed in much more humanitarian pursuits. Images obtained via these satellites can for example provide public health experts with a powerful tool for monitoring and predicting the prevalence of some vector borne diseases, particularly in the developing world.
This field is known as tele-epidemiology. Tele-epidemiology involves the study of human and animal diseases that are transmitted by vectors, which are closely linked to climate and the environment, by using space technology. It combines different types of data that includes physical factors such as temperature and humidity, health data and socioeconomic data (that is typically gathered by more traditional means) with remote sensing data – in other words data gathered by scanning the earth by satellite or high-flying aircraft – such as climatological, environmental and land use data. This allows researchers to analyse the relationships that exist between the climate, the environment and animal and human health in a given area and to determine whether there are links between the infectious diseases and the environment in which they develop. The goal of the process is to provide public health professionals with tools such as risk maps and forecasting models that will allow them to monitor and anticipate epidemics and put mechanisms such as early warning systems and prevention programmes in place.
One such vector borne disease that is particularly relevant to South Africa and its neighbouring countries is malaria. Malaria is a complex parasitic disease that is found mostly in tropical areas and transmitted by mosquitoes of the genus Anopheles. According to the record of the World Health Organization (WHO), 207 million malaria cases and 627 000 deaths were reported worldwide during 2012. Ninety per cent of these deaths occurred in sub-Saharan Africa and 77% of the victims were children younger than five years. More than 10% of the South African population live in the country’s three malaria-endemic provinces, namely Limpopo, Mpumalanga and KwaZulu-Natal.
The vectors of malaria (Anopheles mosquitoes) thrive in warm, moist environments and it is feared that the projected levels of global warming may enable parasite carrying mosquitoes to spread over more provinces of South Africa and in the process expose more people to the disease. A good climate-modelling system for malaria is therefore an important tool for providing early warning on possible malaria outbreaks and for studying the potential impacts of future climate change on the disease. Such a system will also give decision makers the time necessary to deploy intervention methods to help prevent large-scale spread of the disease.
Since the tele-epidemiology concept could be a lever to address the malaria epidemics in southern Africa, a bilateral discussion was initiated between the University of Pretoria Centre for Sustainable Malaria Control (UP CSMC)
and the French National Centre for Space Studies (CNES)
to explore the potential of a joint research programme using remote sensing to help prevent the spread of malaria. This discussion culminated in a workshop co-hosted by the UP CSMC and the French Embassy on 29 and 30 June 2015. The workshop was attended by scientists from various French research institutions such as CNES, the IRD’s UMR Espace pour le Développement (ESPACE-DEV), the Laboratoire d’Aérologie of the Midi-Pyrénées Observatoire, as well as South African partners such as the South African National Space Agency (SANSA) and the Medical Research Council (MRC). The Manager of the Limpopo Province Malaria Control Programme and delegates from the National Department of Health and the World Health Organisation (WHO) also contributed to the discussions. Other delegates included representatives from the universities of Zimbabwe, Mozambique and Reunion, as well as the Pasteur Institute of Madagascar. The objectives of the workshop were to draw the key players of the planned programme together in order to identify suitable partners for collaboration, to define the boundaries of the research programme and to explore funding opportunities. The proposed collaborative programme is currently known as the ‘Remote sensing for malaria control in Africa’ programme, or ReSMaCA.
It is envisioned that research activities between the UP CSMC and their French partners will focus on the expansion of predictive malaria-risk maps to investigate the impacts of climate variability and changes on the occurrence and intensity of malaria epidemics. Some of these research partners already have similar programmes in place in other African countries.
CNES for example has applied a tele-epidemiological conceptual approach to monitor Rift Valley fever (RVF) in Senegal. RVF is a viral disease found essentially in Africa and is – like malaria – spread by mosquitoes. The disease causes very serious economic losses in livestock in the Sahelian region of Senegal annually and could potentially also infect humans. The work done on the project to date has linked the abundance of RVF vectors to the dynamics of ponds in the area, including their associated vegetation cover and turbidity degree. Turbidity is a measure of the degree to which the water loses its transparency owing to the presence of suspended particulates. The more total suspended solids in the water, the murkier it seems and the higher the turbidity. The ponds’ dynamics in turn, is associated with the spatio-temporal variability of rainfall events. One of the project’s successes to date include a brand-new index for the detection of small and temporary ponds. The index was set up using high-spatial SPOT-5 satellite images and the coupling of in-situ measurements and remote-sensing derived products in order to model dynamic zones potentially occupied by mosquitoes (ZPOM). This combines mechanisms linking rainfall variability, the dynamics of ponds and the density of aggressive vectors.
ESPACE-DEV in turn has a malaria project in the Comoros that aims to characterise the spatio-temporal dynamics of malaria, as well as the ecological and social patterns of the disease. Some of the objectives of the project are to build environmental knowledge through remote sensing; to build a spatial database (geo-catalogue) that will be usable by the Ministry of Health; to identify inequalities in the health system by conducting surveys; to determine the possible impact of control actions; and to model the occurrence of malaria in the Comoros statistically. Similarly, the Pasteur Institute of Madagascar’s malaria project on Madagascar uses remote sensing data to map the persistent abnormal malaria situation on the island. The data they have accumulated to date have enabled them to develop – in collaboration with US AID and ESPACE-DEV – a web based Malaria Early Warning System using mobile phones to collect real-time data from the field.
The lessons learnt by UP’s potential partners in projects like the ones mentioned above that have been underway for a while, could prove immensely valuable in making the proposed ReSMaCA programme a success as well.
In addition to the many international partners that will potentially collaborate on the programme, the UP CSMC will also collaborate with various partners at UP such as the Unit for Geo-information and Mapping (UGM) of the Department of Geography, Geo-informatics and Meteorology (GGM)
. The Unit hosts a variety of geospatial datasets and (as representative of UP) also has a Distribution of Spatial Information Agreement with the City of Tshwane. The Department’s Laboratory for Atmospheric Studies (LAS)
, which was launched with support from Eskom and Sasol earlier this year, was also suggested as a collaborative partner for the programme, as the atmospheric modelling undertaken by the Laboratory could provide more detail on the spatial (and temporal) distribution of climates related to malaria outbreaks, while climatic models generated at LAS could serve as an early warning instrument to assist in malaria risk management, for example in relation to weather prediction, seasonal outlooks and climate change projections.
Prof Tiaan de Jager, Director of the UP CSMC, says that innovative methods, available technologies and a creative approach can assist the University of Pretoria to address some of the serious cross-border issues that currently threaten the malaria elimination targets set by the South African government. As a Collaborating Centre of the Medical Research Council (MRC), the UP CSMC is excited about the new partnership with the French institutions and looking forward to combat malaria, using space technologies.
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