Diagnostic target product profile for monitoring and evaluation of soil-transmitted helminth control programmes

Overview

Soil-transmitted helminths are a group of intestinal worms that include Ascaris lumbricoides (giant roundworm), Trichuris trichiura (whipworm), and Ancylostoma spp. (A. duodenale, A. ceylanicum) and Necator americanus (hookworms). Despite the clear biological differences among the different species, their transmission is characterized by the same sequence of events: (i) infected individuals excrete worm eggs through their stool in soil; (ii) under optimal conditions of moisture and temperature the excreted eggs develop into infectious stages; and (iii) finally, infection occurs through oral uptake (Ascaris, Ancylostoma and Trichuris) or skin penetration (Ancylostoma and Necator) of these infectious stages (embryonated eggs and third stage larvae) that reside in the soil and/or in the environment (referring to their common name).

It is estimated that 800 million people worldwide are infected with at least one species of soil-transmit-ted helminth, resulting in a global disease burden of more than 3 million disability-adjusted life years. Given the route of transmission, these infections and their associated disease burden predominate in (sub)tropical countries where optimal climate conditions for egg survival and larval development in the environment, poor socioeconomic status and lack of appropriate access to water, sanitation and hygiene facilitate transmission. Attributable morbidity is mainly associated with infections of moderate-to-heavy intensity and mainly affects children and women of reproductive age. Effects include impaired growth and cognitive development, malnutrition, anaemia and school absenteeism in children, and malnutrition and anaemia in women.

Health ministries currently lack effective tools for monitoring and evaluating programmes to control soil-transmitted helminths. Egg detection can be used, but the cost and challenges of obtaining samples and the need for trained personnel and equipment limit the frequency of monitoring. The purpose of this target product profile is to lead the development of new diagnostic tools to facilitate programme decisions on whether (i) programmes should start preventive chemotherapy, (ii) move to-wards the next phase or ultimately stop preventive chemotherapy, based on WHO’s decision algorithm and (iii) whether soil-transmitted helminths have been eliminated as a public health problem.