Survey data can be collected as part of health surveys (national and sub-national) or during field research for studies on infectious diseases. The surveys are usually led by the Ministry of Health, NGOs or other research institutions, and survey results are published in the format of reports or academic journals along with additional information on geographic location and survey methods.
Survey maps show the location of field surveys. The surveys were identified through searches of electronic bibliographic databases, manual searches of local archives and libraries, and direct contact with researchers. They are useful to graphically show the distribution of survey data and to highlight where such data is lacking. They also illustrate differences in the observed prevalence of worm infection both across the country and sub-nationally (for example, at district level).
For STH, the map shows the location of STH surveys and the reported combined prevalence of infection (with any STH species) across the country. Combined STH prevalence is the reported prevalence of each species, calculated using simple probability and a correction factor that allows for associations between STH species. Where the exact co-ordinates of the survey location are not known, data are shown at a small-area scale, typically a district or province.
The inset map shows the district-level prevalence of infection, calculated as an average of surveys conducted in each district. Districts shaded in grey indicate an absence of survey data.
For schistosomiasis, different types of maps are provided:
- The combined schistosomiasis map shows the location of parasitological schistosome infection surveys across the country. Survey locations are categorized by the maximum prevalence of any schistosome species. The inset maps separately show the survey location and reported prevalence..
- The schistosome species-specific maps show the location of parasitological schistosome infection surveys. An inset map provides a close-up for areas where survey locations are crowded.
- The blood in urine map shows the location of surveys that tested blood in urine, a classic sign of uro-genital schistosome infection. Again, an inset map provides a close-up.
For LF, survey data is categorised as pre-control and contemporary. Pre-control maps show the distribution and prevalence of survey data collected before the implementation of large-scale national control programmes. Contemporary survey data, where they exist, includes only those surveys conducted since the implementation of large-scale national control. This includes data collected during Transmission Assessment Surveys (TAS) and from sentinel survey sites. Where the exact co-ordinates of the survey location are not known, data are shown as implementation unit averages, typically a district.