To Reduce the Global Burden of Human Schistosomiasis, Use ‘Old Fashioned’ Snail Control

Abstract

Control strategies to reduce human schistosomiasis have evolved from 'snail picking' campaigns, a century ago, to modern wide-scale human treatment campaigns, or preventive chemotherapy. Unfortunately, despite the rise in preventive chemotherapy campaigns, just as many people suffer from schistosomiasis today as they did 50 years ago. Snail control can complement preventive chemotherapy by reducing the risk of transmission from snails to humans. Here, we present ideas for modernizing and scaling up snail control, including spatiotemporal targeting, environmental diagnostics, better molluscicides, new technologies (e.g., gene drive), and 'outside the box' strategies such as natural enemies, traps, and repellants. We conclude that, to achieve the World Health Assembly's stated goal to eliminate schistosomiasis, it is time to give snail control another look.

Comparative analysis of time-based and quadrat sampling in seasonal population dynamics of intermediate hosts of human schistosomes

“…There has been increasing attention to schistosomes' snail obligate intermediate hosts with the recent paradigm shift from morbidity control to elimination through transmission interruption following the World Health Assembly 2012 resolution 65.21 on schistosomiasis elimination [6,7]. The analysis of past successes in disease elimination have highlighted the key role of snail control in reaching transmission interruption [8][9][10]. Snail control can be achieved through habitat modification, chemical or plant-based molluscicides [11], or by biological control with snail predators such as fish [12] or prawns [13].…”

“…Most snail population sampling protocols used today were established by research efforts between the 1950's and the 1970's fostered by a strong focus on transmission control through snail population management [10,37,38]. Recent quantitative estimates of snail abundance in the context of schistosomiasis control trials in SSA have principally relied on methods involving active habitat sampling principally using time-based protocols, as opposed to passive methods such as snail traps [31,39].…”

Sm‐p80‐based vaccine trial in baboons: efficacy when mimicking natural conditions of chronic disease, praziquantel therapy, immunization, and Schistosoma mansoni re‐encounter

“…Although these control strategies have shown some promise in certain areas, evident limitations such as sustained reinfection rates, emergence of drug-resistant parasites, and a lack of adequate infrastructure, necessitate the development of a schistosomiasis vaccine to supplement (or even supplant) existing control strategies. [11][12][13][14][15][16][17] Additionally, PZQ is nonprophylactic and only effective against adult parasites; repeated treatments are therefore required to alleviate the burden of schistosomiasis in endemic areas. 18,19 A Schistosoma mansoni calpain (Sm-p80)-based vaccine has consistently shown protection against schistosomiasis in rodent and nonhuman primate models of infection and disease, making it a leading vaccine candidate; it is currently being prepared for Phase I/II human clinical trials in 2019.…”

Co-infecção Plasmodium falciparum e Schistosoma haematobium: papel dos genes HLA não-clássicos de classe I (HLA-G, -E e -F) na suscetibilidade à malária

“…Other control strategies are available and already adopted and used by various countries with successful results. For instance, the snail control implemented by various countries including the African ones has provided a high rate of schistosomiasis control (from 80 to 100%) (Sokolow et al 2018). However, in some countries (specially from West Africa, including Benin), the snail control strategy is still disappointing (Sokolow et al 2018), indicating that, depending on the country and its geographical localization, this control maybe more difficult than in those countries.…”

“…For instance, the snail control implemented by various countries including the African ones has provided a high rate of schistosomiasis control (from 80 to 100%) (Sokolow et al 2018). However, in some countries (specially from West Africa, including Benin), the snail control strategy is still disappointing (Sokolow et al 2018), indicating that, depending on the country and its geographical localization, this control maybe more difficult than in those countries. Thus, as precaution, Sokolow et al suggested that it would be important to combine the preventive chemotherapy (to firstly interrupt the infection in human) with the snail control (Sokolow et al 2018).…”