FOCAL-NTDs is an MRC funded project whose goal is to develop a framework that enables neglected tropical disease (NTD) control efforts to be targeted more effectively, with a specific focus on schistosomiasis, human African trypanosomiasis (also known as HAT or sleeping sickness), and lymphatic filariasis (LF). Further details on these three diseases can be found on the About NTDs pages.
Disease control programmes, particularly those operating in low-income countries, require knowledge of the geographical distribution of the target disease in order to establish where control interventions are most needed. In instances where the disease risk is approximately constant across a geographical area (i.e. spatially homogeneous), programmes are able to evenly distribute interventions amongst the population. However, disease risk can often be very variable (i.e. spatially heterogeneous), particularly in the case of parasitic diseases in which the relationship between the parasite and the human host is dependent on the surrounding environment. In these instances a ‘blanket’ intervention approach isn’t sufficient to eliminate a disease from an area, as resources are wasted in areas where there is no disease risk, and are not adequately focused to completely remove disease ‘hotspots’.
For NTDs that are controlled using preventive chemotherapy (schistosomiasis, lymphatic filariasis, soil-transmitted helminths, onchocerciasis, trachoma), current approaches for establishing where to target control interventions focus on establishing whether the disease prevalence within an implementation unit (often a district) are above certain thresholds with little regard given to the variability of disease risk within the implementation unit. Treatment is then delivered to all of the eligible treatment population, regardless of whether their local area has a high or low disease transmission risk.
As the prevalence of these diseases decreases with successive rounds of treatment, their geographical distribution will potentially become more heterogeneous (of focal), and current approaches to prevalence surveys will no longer be adequate as they may miss important foci and conclude that a disease is non-endemic when hotspots still exist. Hence, cost-effective, practical approaches to estimating the spatial distribution of disease risk within an implementation unit will be needed so that interventions can be targeted towards these hotspots.
HAT is already a very focal disease with very limited treatment options, hence an alternative approach to controlling this disease is to control its vector, the tsetse fly. Whilst the context differs, the underlying problem of how to identify areas of high disease transmission risk i.e. areas inhabited by infected tsetse flies, remains the same.
The aim of this project is to develop a framework that enables geographical variability in disease risk to be established and monitored more effectively. This project will focus on the three NTDs stated above and coinfections with malaria in order to demonstrate the flexibility of the framework being developed.
Local level risk maps for each of these diseases will be produced using data provided by project collaborators from endemic countries, including Malawi and Uganda. These maps will combine disease/vector/intermediate host information with information on the risk factors of the diseases in question, which may or may not be geographically referenced. Geographically referenced risk factors could include those that influence the presence and/or density of the disease’s vector/intermediate host, or influence how likely a person is to come into contact with the vector/intermediate host. Using the example of schistosomiasis, this may include factors such as the distance of the village to the nearest freshwater source, factors influencing the intermediate host/parasite ability to survive and breed (e.g. altitude, temperature, vegetation) and information on control activities have been implemented in the area.
Traditional methods of collecting local level disease risk data use survey teams to collect information, with surveys often being expensive, time-consuming and logistically difficult to undertake in rural areas of developing countries. In addition to developing risk maps based on previously collected information, alternative methods for obtaining local level disease-related data will be explored.
Two approaches will be considered.
- Firstly, more efficient spatial sampling methods for determining which sites should be surveyed will be developed. These methods will be ‘flexible’ in the sense that the selection of sites to sample will be done iteratively, and will be selected strategically in order to reduce the uncertainty in the estimated geographical distribution of disease risk in the study area.
- The second approach focuses on using community members to collect disease-related information, as opposed to a dedicated survey team. Community members are becoming increasingly involved in disease control activities in developing countries, and this has been shown to improve intervention coverage and acceptability. This project will explore ways in which community members can more
directly contribute to disease control activities through the development of mobile phone-based surveillance and reporting tools. Community members in Malawi and Uganda will be trained to report information such as preventive therapy coverage (for schistosomiasis and LF) and vector control (malaria and HAT) respectively.