Mapping trachoma: data collection and approval

Image property of Dominic Nahr/Magnum/Sightsavers

GAHI’s sister website, the Global Atlas of Trachoma (GAT), is an open-access resource on the geographical distribution of trachoma. Rebecca Mann Flueckiger is GIS Data Manager at the International Trachoma Initiative and she writes for GAHI about the role of technology in mapping trachoma and the approval process required to publish data in the GAT.

7 August 2013

GAHI’s sister website, the Global Atlas of Trachoma (GAT), is an open-access resource on the geographical distribution of trachoma, another neglected tropical disease and a leading cause of blindness globally. To update and expand its existing data, the Global Trachoma Mapping Project (GTMP) was launched in 2012 with support from the International Trachoma Initiative (ITI) at the Task force for Global Health in Decatur, Georgia, United States. Rebecca Mann Flueckiger is GIS Data Manager at ITI and she writes for GAHI about the role of technology in the GTMP and the approval process required to publish data in the GAT.

Trachoma is an eye infection that causes chronic inflammation of the eyelid. Repeated re-infection scars the eyelid, making it turn inward and causing the eyelashes to scratch the eyeball. Over time, this damages the cornea and ultimately leads to blindness. At present, we estimate that trachoma affects more than 21 million people, with 180 million people worldwide living in trachoma-endemic areas at risk of becoming blind. Once we are able to fully and accurately map the scale and location of neglected tropical disease (NTD), we will be able to more effectively deploy resources, including treatment, where they will have maximum impact.

Data on the distribution of trachoma is publicly available on the Global Atlas of Trachoma (GAT). The data contained in the atlas comes from many different sources, including country reports, published research and expert opinion. A recently published paper analyzing the burden of trachoma in Africa estimated that 129.4 million people live in areas of the continent where blinding trachoma is confirmed to occur. This work highlighted how the disease varies greatly across the continent, with clinical signs most common in the Sahel area of West Africa and the savannah areas of East and Central Africa. However, the work further highlighted that there remains a gap of knowledge about the prevalence of trachoma in many suspected endemic areas.

Homepage of the Global Atlas of Trachoma

Technology will be the key for the rapid success of this massive undertaking. For data collection and reporting the GTMP used the
LINKS System, a group of open source tools used to enable simple data collection on Android-powered smartphones, and reporting through a secure website. A geographic component, LINKS Maps, was added to this system to enhance the process. LINKS Maps is a web-based mapping system that links existing data sources to online maps powered by esri.To fill this knowledge gap, the Global Trachoma Mapping Project (GTMP) was launched in the fall of 2012 with the goal of identifying where people are living at risk of the disease and intervention is needed. This is believed to be the largest global mapping campaign ever attempted, examining a sample of 4 million people in 30 countries in less than 2 years.

GPS coordinates are collected as part of the GTMP exercise. A live map of the points being collected is available to the data collection team through the reporting website. These maps provide a visual to ensure that appropriate spatial coverage was achieved. Providing a geographic representation of data has proved valuable to ensure quality of the data submitted as well as to give a visual reference to those responsible for approving the release of the data into the public domain. 

Point map

Once the data collection for an evaluation unit is complete, the data must be reviewed and approved for release by the appropriate Ministry of Health representatives. This review process is a challenge because the sampling strategy requires that the evaluation unit represent roughly 250,000 people and have consistent geographic and socio-economic makeup. An evaluation unit is the geographic area being surveyed. To this end, in some countries administrative boundaries were combined or split to make the evaluation units fit these criteria. Without a map reference, this manipulation of boundary areas makes it difficult for the Ministry of Health representatives to know what area the data represents.

To overcome this obstacle, maps were created to illustrate the boundaries of the evaluation units. These “approval maps” are available on the reporting website. The website is accessible to members of the GTMP team and Ministry of Health representatives. These are dynamic maps, meaning the boundaries change color depending on the stage of the approval process:

  • Red: data is still being collected
  • Orange: data is being cleaned
  • Yellow: MoH has approved the sampling frame and methodology
  • Blue: MoH has given final approval for release of the data

Approval map

Once the survey area turns blue, it is deemed ready for the public domain and input into the Global Atlas of Trachoma, as well as The NTD Mapping Tool currently being developed. As the GTMP continues collecting data, the GAT will continue to be updated to show the latest, most reliable maps of trachoma prevalence in Africa. This will allow ministries and international organizations to better target their interventions, with the ultimate goal of eliminating trachoma by 2020

Rebecca Mann Flueckiger