Jorge Cano Ortega is a research fellow within the GAHI team and an expert on GIS and lymphatic filariasis. He is lead author on a recent paper explaining the creation of the first global map of LF transmission limits and distribution, published in Parasites & Vectors. In this blog entry, he describes the creation of global and additional regional and country maps for LF.
The global elimination of lymphatic filariasis (LF) requires a detailed understanding of the geographical distribution of transmission in order to guide control and post-control surveillance.
We have recently developed a global atlas of lymphatic filariasis with maps of distribution and environmental limits of transmission. This work is valuable in several ways:
• It provides a basis for tracking and interpreting progress in control over time.
• It can define the pre-control transmission limits.
• It can inform the intensity and duration of control.
Methodology and findings
Data were identified for 66 of the 72 countries currently endemic for LF and for a further 17 countries where LF is no longer endemic. Our map highlights a restricted and highly heterogeneous distribution in sub-Saharan Africa, with transmission more widespread in West Africa compared to east, central and southern Africa where pockets of transmission occur. Contemporary transmission occurs across much of South and South-east Asia and the Pacific. Interestingly, the risk map reflects environmental conditions suitable for LF transmission across Central and South America, including the southern States of America, although active transmission is only known in a few isolated foci.
Regional and country maps based on the global map of predicted environmental suitability for LF are now available from the Global Atlas of Helminth Infections. These maps can be a helpful tool for decision-makers of endemic countries, like control programme managers:
• those who are yet to start mapping surveys and therefore need to identify suitable areas for LF transmission;
• those who are implementing MDA interventions and need a benchmark to assess progress.
It is important to keep in mind that these maps do not necessarily reflect current distribution as our model did not account for any potential impact of control interventions on the spatial distribution of the disease. Further investigations are underway to produce more accurate and contemporary maps of LF distribution.
If you have any questions or want more information about our LF maps, please contact jcano.ortega [at] lshtm.ac.uk (Jorge).