A new study, led by Dr Jorge Cano and Dr Paula Moraga, details predictive models of lymphatic filariasis (LF) prevalence and transmission intensity across sub-Saharan Africa.
A new paper in Parasites & Vectors presents the first predictive model of LF transmission intensity based on estimates of the basic reproductive number (R0). Using a suite of environmental and demographic data, and prevalence surveys compiled in the Global Atlas of Helminth Infection, spatiotemporal multivariate models were fitted separately for microfilaraemia (mf) prevalence and antigenaemia prevalence within a Bayesian framework and used to make predictions for non-sampled areas.
The intensity of transmission quantified by R0 was inferred by linking the map of predicted mf prevalence to mathematical models of LF transmission dynamics. The intensity of LF transmission was found to be highly heterogeneous in sub-Saharan Africa prior to the implementation of large-scale MDA-based programmes.
Surveillance efforts following MDA interventions should consider geographical variation in transmission intensity at baseline, as well as the number of MDA rounds and population coverage achieved. Further control efforts may be required in areas of higher transmission intensity; and conversely, interruption of transmission might be achieved earlier in areas of low transmission intensity. The development of microfilaraemia, antigenaemia and R0 maps can help inform future LF surveillance programmes by identifying areas of higher transmission intensity, which may require enhanced and tailored interventions.
Co-lead author of the study, Dr Cano says: “Monitoring and post-MDA surveillance are key phases in the pathway towards the elimination of LF. Whereas the former enables programme managers to determine if they are on track to meet a set target, the latter helps inform whether prevalence of infection has been lowered to a level where recrudescence is unlikely to occur, even after interrupting MDA. The reliability of the outcome provided by monitoring and post-MDA surveillance relies on a good understanding of transmission and its underlying factors prior to intervention. To address this, GAHI, together with partners from the NTD Modelling Consortium, have developed predictive maps of LF prevalence and transmission intensity for the SSA region, through a combination of geostatistical and mathematical models. Consistent with our open access approach, country maps of predicted microfilaraemia and antigenaemia prevalence and transmission intensity have been produced and are already available at the project website”
Read the paper in Parasites & Vectors.
Authors: Paula Moraga, LSHMT (UK), Jorge Cano Ortega, LSHMT (UK), Rebecca F Baggaley, LSHMT (UK), Sammy M Njenga, KEMRI (Kenya), Birgit Nikolay, LSHMT (UK), Emmanuel Davies (Nigeria MoH), Maria Rebollo, Task Force for Global Health (US), Rachel L Pullan, LSHMT (UK), Moses J Bockarie, Liverpool School of Tropical Medicine (UK), TD Hollingsworth, University of Warwick (UK), Manoj Gambhir, Monsah University (Australia), Simon J Brooker, LSHTM (UK)