Assessing the epidemiology of soil-transmitted helminths during a transmission assessment survey (TAS)

Overview

 Soil-transmitted helminths infect more than 2 billion people in more than 100 countries, adversely affecting nutritional status and impairing cognitive processes. Their geographical distribution overlaps with at least one of the other parasitic neglected tropical diseases, including lymphatic filariasis.

When a programme for the elimination of lymphatic filariasis is implemented in an endemic area, the distribution of albendazole plus ivermectin or diethylcarbamazine also affects soil-transmitted helminthiases. After at least 5 or 6 years of implementation of this intervention, normally a transmission assessment survey is conducted to confirm that the prevalence of lymphatic filariasis is below a level at which recrudescence is unlikely to occur and the intervention can be stopped.

At this stage, it is important to have information about the epidemiological situation of soil-transmitted helminthiases in the area and, in particular, to determine whether administration of albendazole and mebendazole for the control of these infections should be continued in the absence of further mass drug administration for lymphatic filariasis.

This manual provides support to programme managers in collecting soil-transmitted helminths, including sample size and critical cut-offs, to take decisions on the treatment option in the event that the programme for the elimination of lymphatic filariasis is interrupted.