Defining STH transmission interruption
In order to quantify epidemiologic and operational targets for STH transmission interruption, the DeWorm3 Project has established a series of studies to:
1) define an STH transmission breakpoint
2) develop the tools and methods necessary to operationally measure STH transmission interruption
3) identify the prevalence and intensity of STH in an area believed to have achieved STH elimination
History indicates that interruption of STH transmission may be possible. Specifically, STHs were previously highly prevalent in the southeastern United States, South Korea and Japan and sustained control efforts may have led to the interruption of STH transmission in all of these contexts.
DeWorm3, in partnership with Nagasaki University, is conducting targeted prevalence surveys in Nagasaki Prefecture to identify potential persistent STH infections, correlates of infection, and factors influencing community member participation in STH prevalence surveys in areas considered to be at minimal risk.
In order to define an STH transmission breakpoint in areas with active STH transmission, the Modelling and Trial Simulation support unit at Imperial College London has conducted several groundbreaking mathematical modeling studies. These studies have been used to inform identification of: an optimal intervention (community-wide twice-yearly mass drug administration, MDA), target benchmarks for age-stratified treatment coverage, and a prevalence threshold of 2% after which it is believed that sustained transmission will no longer be possible.
Mathematical models indicate that high treatment compliance is critical for interrupting disease transmission. In collaboration with the Centro de Investigación Veterinaria de Tandil (CIVETAN), the DeWorm3 Project is developing a urinary assay to measure albendazole metabolites. The assay will be utilized during DeWorm3 clinical trial coverage surveys to validate reported treatment coverage.
In low transmission settings with a majority of low intensity infections, it is crucial to apply diagnostic methods with the highest sensitivity to successfully detect all remaining infections. In collaboration with Smith College, the DeWorm3 project identified the best ways of preserving stool for subsequent molecular evaluation by qPCR and developed pooling strategies which help to reduce cost and enhance feasibility of molecular testing at site level.
More information on DeWorm3 mathematical modeling, urinary assays, and qPCR laboratory science can be found here.