Developing methods to assess the impact of malaria interventions upon transmission and the progress towards elimination
The first aim of this project is to develop and adapt methods used for reproduction number estimation in epidemic models to estimate the changes in malaria transmission which have occurred in an area of Western Kenya. This will provide estimates of the additional control necessary to achieve elimination in an area of intense transmission with high LLIN coverage. It will also provide insights into the direct and indirect effects of insecticide treated nets and how this varies during a long-term intervention.
The second objective is to estimate the impact of different control strategies involving the mass administration of artemisinin combination therapy on malaria transmission during a forthcoming trial in the same area. The detailed data likely to be collected during this trial will be used to estimate transmission at a high spatial and temporal resolution. Using the results from the first part of the project of the level of transmission and trajectory of changing transmission prior to the trial, I will then assess the extent to which reductions in prevalence are likely to be sustainable and the prospects for elimination, both within the study area and more generally.
Measuring progress towards malaria elimination requires an estimate of the reduction in transmission that has occurred over time and the proximity to the threshold reproduction number value of one. However, these changes are not linearly related to measures of disease prevalence and burden (the quantities often used to track progress).
In this project, Dr Patrick Walker, a researcher at the Department of Infectious Disease Epidemiology, Imperial College, will use mathematical models of the spread of malaria to estimate the changes in transmission that occur during this trial to assess the progress being made towards local elimination of the disease. This will first involve developing a statistical technique which is able to estimate changes in transmission intensity during a previous trial of protective nets in the same area. This work will also allow him to investigate the extent to which the disease spreads from one village to another and how this is affected by the presence of nets within different areas. This technique will then be adapted and applied to the different arms of the drug trial, taking into account changes in transmission up to the beginning of the trial.
In the event that the mass administration of anti-malarials proves effective as a tool for helping Western Kenya to eliminate malaria, this research will help to further define the criteria by which to judge where else in the world the intervention could be effective. Alternatively, if the intervention does not prove effective the work will provide an indication of the additional level of control required to achieve elimination. Moreover, monitoring whether transmission changes throughout the trial could provide an indication as to whether the effectiveness of anti-malarial drugs remains the same throughout the trial, which is an important consideration in light of concerns about drug resistance.