An important step in planning for school-based deworming is determining location, prevalence, and species of worms. As many areas will not have worms, not all children need to be treated. Mapping allows targeting to those who need treatment and thus maximizes program cost-effectiveness. Schistosomiasis and STH will both need to be mapped as the treatment strategy for each is different and often one can be present without the other (see table below).

There has already been appraisal of many areas and predictive maps are available on the Global Atlas of Helminth Infections. We may also be able to assist with mapping existing data and identifying where additional data is needed.

Stages for Mapping Worms and Targeting School-based Deworming

1. Existing data and surveys should be collected and mapped.
2. This should be combined with predictive data, which can identify areas where worm transmission is not occurring.
3. Rapid appraisal can be carried out for areas where data does not exist or is out of date, but where it is shown worm transmission could be occurring.
4. Based on the data, the country’s population, and administrative levels, target areas should be decided. For example, targeting all schools in a district/zone for STH or by focal area for schistosomiasis.
5. Data on schools and school populations can be mapped onto the same map to form a useful planning tool.

School-based deworming can be geographically targeted according to the WHO guidelines (WHO 2004) set out below.

Prevalence thresholds on STH and schistosomiasis for mass school-based deworming