Schistosomiasis and soil-transmitted helminthiases: progress report, 2022

Overview

Human schistosomiasis is caused mainly by 3 schistosome species: Schistosoma haematobium, S. mansoni and S. japonicum. S. guineensis, S. intercalatum and S.  mekongi have a highly localized distribution in Central Africa and along the Mekong River in South-East Asia, respectively. Soil-transmitted helminthiases (STH) are infections caused by 4 parasite species: Ascaris lumbricoides, Trichuris trichiura, Ancylostoma duodenale and Necator americanus. The 2 latter species are indistinguishable microscopically and are usually reported together as “hookworms”. Schistosomiasis and STH are neglected tropical diseases (NTDs) and are transmitted mainly in areas with poor access to clean water and sanitation. The presence of an intermediate snail host in water is essential to allow Schistosoma to complete their life cycle. Schistosomiasis and STH can cause significant morbidity, including anaemia, nutritional disturbances and, in the case of schistosomiasis, granuloma, organ pathology and cancer, and an increased risk of acquisition of HIV. In women, urogenital schistosomiasis may cause vaginal bleeding, pain during sexual intercourse and nodules in the vulva, now described as female genital schistosomiasis. Groups at risk for STH and schistosomiasis are those in need of micronutrients: preschool-aged children (pre-SAC, 1–4 years of age), school-aged children (SAC, 5–14 years), women of reproductive age (WRA) and, in addition for schistosomiasis adult and entire communities in high-risk areas.

In countries in which schistosomiasis and STH are endemic, WHO recommends improved access to clean water and sanitation, behavioural change interventions and preventive chemotherapy (PC), which is periodic treatment with anthelminthic medicines (albendazole or mebendazole for STH and praziquantel for schistosomiasis) to populations at risk. WHO also recommends snail control and environmental management to control and eliminate schistosomiasis.