Integrating ecological approaches to interrupt schistosomiasis transmission: opportunities and challenges

Abstract

Background: The development of agenda for global schistosomiasis elimination as a public health problem generates enthusiasms among global health communities, motivating great interests in both research and practice. Recent China-Africa schistosomiasis control initiatives, aiming to enhance collaboration on disease control in African countries, reflect in part that momentum. Yet there is a pressing need to know whether the Chinese experiences can be translated and applied in African settings.

Main body: China's remarkable achievements in schistosomiasis control programme, associated experiences and lessons, have much to offer to those combating the disease. Central to the success of China's control programmes is a strategy termed "integrated control" - integrating environmental approaches (e.g. improved sanitation, agricultural and hydrological development and management), which target different phases of the parasite transmission system, to chemical-based drug treatment and mollusciciding. Yet, despite significant measurable public health benefits, such integration is usually based on field experience and remains largely uncharacterized in an ecological context. This has limited our knowledge on relative contributions of varying components of the integrated control programme to the suppression of disease transmission, making it challenging to generalize the strategy elsewhere. In this opinion article, we have described and discussed these challenges, along with opportunities and research needs to move forward.

Conclusions: There is an urgent need to formalize an ecological framework for the integrated control programme that would allow research towards improved mechanistic understanding, quantification, and prediction of the control efforts.

Keywords: Ecological framework; Integrated control; Schistosomiasis; Transmission interruption.

Fig. 1

Integrated interventions in the ecological framework. Integrated interventions, targeting various aspects of parasite transmission, primarily consist of infectious source control (e.g. chemotherapy on infected humans and/or animals, animal and waste management through improved sanitation), control of snail intermediate host (e.g. mollusciciding using niclosamide, agricultural and hydrological management, and afforestation), and exposure control (e.g. behavioral change through hygiene improvement, and agricultural and hydrological management). However, the relative contribution of integrated intervention framework to the suppression of schistosomiasis remain largely uncharacterized both mechanistically and quantitatively. This limits the generalizability of these intervention approaches to endemic areas elsewhere. The ecological framework emphasizes dynamic interactions among different system components as illustrated in the figure. Such framework can allow the potential usage of different tools to quantify these interventions and associated impacts. The commonly used approach is dynamic modeling, in which these interventions can be specifically factored. The widely used metric for transmission of infectious diseases, R_e, effective reproductive number (or transmission potential) may be used to assess the impacts of the integrated interventions on disease transmission and efforts needed to eliminate the transmission. While ecology-based intervention including environmental modification through water resources projects or agricultural projects will be the major components to provide long-term effectiveness and precision intervention towards schistosomiasis transmission interruption. Biological and mechanical control methods such as application of extracted plant molluscicides and introduction of natural predators (e.g. snail eating fishes or prawns) of intermediate hosts can be harnessed to effectively control snails

Fig.  2

The WordCloud maps of ecological intervention applied in the national schistosomiasis control programmes in China (a) and Africa (b). Two WordClouds were generated in R using the following steps: (1) The search terms of (“ecological intervention” AND “schistosomiasis intervention” AND “China/Africa”) were used to search PubMed database (2)Searched results including titles and abstracts in all literatures of PubMed database, were loaded into tidytext, dplyr, stringr and wordcloud2 packages in R solfware (version 3.5.1), and finally produced interactive wordclouds, with the assistance of China and Africa contour maps.