Integrated risk mapping and targeted snail control to support schistosomiasis elimination in Brazil and Cote d'Ivoire under future climate change

Lead Research Organisation: University of St Andrews
Department Name: Biology


Schistosomiasis is a debilitating, poverty-linked disease caused by a parasitic worm with a complex life cycle: its transmission requires infection of an obligate intermediate freshwater snail host that is parasitized by larvae from eggs released by infected people. In turn, infected snails shed other parasitic larval stages that eventually reinfect people exposed to parasite-contaminated waters whilst doing their daily chores. The inflammatory processes caused by schistosome eggs cause abdominal pain, diarrhea, blood in stool or urine, that lead to chronic anemia, cognitive impairment in children, growth stunting, infertility, a higher risk of contracting HIV in women and, at high levels of infection, to death from liver failure or bladder cancer. With 800 million people at risk and more than 200 million infected, the vast majority of which are school age children, schistosomiasis is one of the most important, but also most neglected tropical diseases.

As both the freshwater snails and the parasite larvae are ectotherms, they have limited ability to thermoregulate . Therefore, their survival, reproduction and dispersal are influenced even by small changes in temperature and temperature variability. Projected climate change is emerging as one of the most powerful drivers of schistosomiasis transmission by altering the geographical distribution of the parasite and its snail hosts and the associated risk of human infections. Understanding climatic, environmental and socio-economic drivers of schistosomiasis and developing novel ecological solutions to fight the disease, improve health, increase food security and alleviate poverty is a scientific and public health priority and will benefit the health of millions of people where schistosomiasis is endemic.

We have three main goals: FIRST, we intend to investigate the effect of increasing temperatures, temperature variability and shift in precipitation patterns due to climate change on the dynamics of snail-born schistosomiasis, a debilitating parasitic disease of poverty affecting more than 200 million people worldwide. We will focus on Brazil and Cote d'Ivoire for these compelling reasons: Brazil suffers the highest schistosomiasis burden in the Americas, with an estimated 2-6 million people infected by the S. mansoni worm. Cote d'Ivoire has a high disease prevalence with an estimated 4 million people infected by S. hameatobium and S. mansoni. Projected climate change - along with growing human population, deforestation, expansion of agriculture and of marginal urban settings and the development of dams and irrigation canals known to be associated with increased schistosomiasis risk caused by habitat expansion for, and extirpation of natural predators of, the snail intermediate host - make these two countries particularly vulnerable to this parasitic disease. We will use a hybrid approach integrating species distribution models accounting for the most relevant socio-economic and environmental drivers of schistosomiasis with temperature-driven, process-based mathematical models of the parasite and its intermediate snail hosts to produce maps of present and future risk for schistosomiasis under climate change. SECOND, we intend to conduct initial feasibility and nutritional studies and market analyses of aquaculture of freshwater prawns native of Brazil and of Cote d'Ivoire with the goal of using them as novel biological control agents of schistosome's snail host while, at the same time, promoting the development of small-scale aquaculture businesses. THIRD, to track future changes in the distribution and abundance of the snail hosts, we will develop machine learning algorithms that enable computer vision as an "environmental diagnosis" tool for the quick and accurate identification of potential schistosome-host snails and parasites from field-acquired cellphone images, trained on thousands of images that have been identified to species by DNA barcoding and PCR-RFLP.

Planned Impact

Through the network of relationships of PI and co-PI, the freely available InVEST software module will be presented to the World Bank, the Asian, African and South American Development banks and the Global Environmental Facility funding mechanism and other governmental and non-governmental institutions involved in international cooperation and supporting the development of water management infrastructures in tropical and subtropical countries where schistosomiasis is or can become endemic. Our vision is that this new InVEST module can be used in the Environmental and Social Impact Assessment procedures usually required to approve the construction of water management infrastructure in tropical and subtropical countries where schistosomiasis is endemic or could become so.

We will develop an outreach program to disseminate the results of our work well beyond the restricted academic community working on schistosomiasis control. We will regularly update the followers of the DeLeo Lab and Hopkins Marine Station Facebook page, the website of the Woods Institute for the Environment, and publish popular scientific articles, such as Science Journal for Kids ( We will also organize joint activities between classes based in the US (initially in at the Monterey Bay in California) and parallel classes in Cote d'Ivoire and Brazil, and use foldscope technology developed by Stanford's Manu Prakash as a tool to introduce elementary students to the wonders of the microscopic world and the infection risk associated with waterborne pathogens and parasites. The work will be used in school outreach programmes in the UK through Science Fairs for primary pupils, school visits for High School pupils and Pint of Science events for adults which are run annually.

A major goal of the proposed research program is to train future professionals who combine a strong academic background with an ability to work in diverse and interdisciplinary settings towards solutions to ecological, environmental and public health problems. The proposed research will provide training in interdisciplinary research for at least three postdoctoral researchers, two graduate students, and several undergraduate students supported through this project. Additional graduate and undergraduate students will be involved through existing programs supporting interdisciplinary training and women and minorities participation, including, at Stanford, E-IPER (PhD), VPUE and MUIR fellowships (undergrad) and for undergraduate, graduate and post doctoral students in Senegal. Students and postdocs will be co-advised and will interact extensively with co-PIs and senior personnel, and will actively participate in the design, field activities, analysis, publication and communication of the proposed research program.


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