Schistosomes, snails and climate change: Current trends and future expectations

Stensgaard, Anna‐Sofie; Vounatsou, Penelope; Sengupta, Mita E.; Utzinger, Jürg

doi:10.1016/j.actatropica.2018.09.013

Cited by 83 publications

(65 citation statements)

References 67 publications

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“…Additionally, early detection of emerging schistosomiasis outside the normally considered endemic range areas using eDNA could be useful to help prevent the disease from spreading. This could, for instance, be highly relevant in situations where schistosomiasis is moving into new territories, as seen recently in Corsica (France) in Europe due to substantial human migration from endemic transmission areas (58,59), or due to climate change making new areas suitable for the establishment of both intermediate host snail species and the parasite (60).…”

Section: Refs 38 43 and 50mentioning

confidence: 99%

Environmental DNA for improved detection and environmental surveillance of schistosomiasis

Sengupta

Hellström

Kariuki

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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107

113

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Schistosomiasis is a water-based, infectious disease with high morbidity and significant economic burdens affecting >250 million people globally. Disease control has, with notable success, for decades focused on drug treatment of infected human populations, but a recent paradigm shift now entails moving from control to elimination. To achieve this ambitious goal, more sensitive diagnostic tools are needed to monitor progress toward transmission interruption in the environment, especially in low-intensity infection areas. We report on the development of an environmental DNA (eDNA)-based tool to efficiently detect DNA traces of the parasite Schistosoma mansoni directly in the aquatic environment, where the nonhuman part of the parasite life cycle occurs. This is a report of the successful detection of S. mansoni in freshwater samples by using aquatic eDNA. True eDNA was detected in as few as 10 cercariae per liter of water in laboratory experiments. The field applicability of the method was tested at known transmission sites in Kenya, where comparison of schistosome detection by conventional snail surveys (snail collection and cercariae shedding) with eDNA (water samples) showed 71% agreement between the methods. The eDNA method furthermore detected schistosome presence at two additional sites where snail shedding failed, demonstrating a higher sensitivity of eDNA sampling. We conclude that eDNA provides a promising tool to substantially improve the environmental surveillance of S. mansoni. Given the proper method and guideline development, eDNA could become an essential future component of the schistosomiasis control tool box needed to achieve the goal of elimination.

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Section: Refs 38 43 and 50mentioning

confidence: 99%

Environmental DNA for improved detection and environmental surveillance of schistosomiasis

Sengupta

Hellström

Kariuki

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

107

113

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“…Studies of both prawns and crayfish remind us that a more thorough exploration of the interface between aquaculture, schistosomiasis transmission, and biological control efforts is required. Aquaculture activities, which will be increasingly in demand in tropical Africa, 74 are likely to directly and indirectly affect schistosome-transmitting snails in ways as yet little studied or appreciated. 75,76 For instance, we noted at Sirikwa Dam near the town of Eldoret that crayfish were abundant and schistosome-transmitting pulmonate snails were absent in the late 1980s-early 1990s.…”

Section: Lessons Learnedmentioning

confidence: 99%

Snail-Related Contributions from the Schistosomiasis Consortium for Operational Research and Evaluation Program Including Xenomonitoring, Focal Mollusciciding, Biological Control, and Modeling

Allan

Shaali

Tian-Bi

et al. 2020

The American Journal of Tropical Medicine and Hygiene

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The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was created in 2008 to answer questions of importance to program managers working to reduce the burden of schistosomiasis in Africa. In the past, intermediate host snail monitoring and control was an important part of integrated schistosomiasis control. However, in Africa, efforts to control snails have declined dramatically over the last 30 years. A resurgence of interest in the control of snails has been prompted by the realization, backed by a World Health Assembly resolution (WHA65.21), that mass drug administration alone may be insufficient to achieve schistosomiasis elimination. SCORE has supported work on snail identification and mapping and investigated how xenomonitoring techniques can aid in the identification of infected snails and thereby identify potential transmission areas. Focal mollusciciding with niclosamide was undertaken in Zanzibar and Côte d'Ivoire as a part of elimination studies. Two studies involving biological control of snails were conducted: one explored the association of freshwater riverine prawns and snail hosts in Côte d'Ivoire and the other assessed the current distribution of Procambarus clarkii, the invasive Louisiana red swamp crayfish, in Kenya and its association with snail hosts and schistosomiasis transmission. SCORE also supported modeling studies on the importance of snail control in achieving elimination and a meta-analysis of the impact of molluscicide-based snail control programs on human schistosomiasis prevalence and incidence. SCORE's snail control studies contributed to increased investment in building capacity, and specimens collected during SCORE research deposited in the Schistosomiasis Collections at the Natural History Museum (SCAN) will provide a valuable resource for the years to come.

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“…Currently, massive treatment with praziquantel and improving sanitation appear the best way to control the disease. However, new foci are appearing, and other are re-emerging probably due to global warming [ 38 , 39 ] and mass human migration [ 40 ], but also to the emergence of drug-tolerant schistosomes [ 41 , 42 ]. In this context, snail control appears to be a crucial strategy to ensure a sustainable control and elimination of schistosomiasis.…”

Section: Discussionmentioning

confidence: 99%

Molluscicidal and parasiticidal activities of Eryngium triquetrum essential oil on Schistosoma mansoni and its intermediate snail host Biomphalaria glabrata, a double impact

et al. 2020

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Background Freshwater snails are the intermediate hosts of a large variety of trematode flukes such as Schistosoma mansoni responsible for one of the most important parasitic diseases caused by helminths, affecting 67 million people worldwide. Recently, the WHO Global Vector Control Response 2017–2030 (GVCR) programme reinforced its message for safer molluscicides as part of required strategies to strengthen vector control worldwide. Here, we present the essential oil from Eryngium triquetrum as a powerful product with molluscicide and parasiticide effect against S. mansoni and the snail intermediate host Biomphalaria glabrata. Methods In the present study, we describe using several experimental approaches, the chemical composition of E. triquetrum essential oil extract and its biological effects against the snail B. glabrata and its parasite S. mansoni. Vector and the free-swimming larval stages of the parasite were exposed to different oil concentrations to determine the lethal concentration required to produce a mortality of 50% (LC50) and 90% (LC90). In addition, toxic activity of this essential oil was analyzed against embryos of B. glabrata snails by monitoring egg hatching and snail development. Also, short-time exposure to sublethal molluscicide concentrations on S. mansoni miracidia was performed to test a potential effect on parasite infectivity on snails. Mortality of miracidia and cercariae of S. mansoni is complete for 5, 1 and 0.5 ppm of oil extract after 1 and 4 h exposure. Results The major chemical component found in E. triquetrum oil determined by GC-FID and GC/MS analyses is an aliphatic polyacetylene molecule, the falcarinol with 86.9–93.1% of the total composition. The LC50 and LC90 values for uninfected snails were 0.61 and 1.02 ppm respectively for 24 h exposure. At 0.5 ppm, the essential oil was two times more toxic to parasitized snails with a mortality rate of 88.8 ± 4.8%. Moderate embryonic lethal effects were observed at the concentration of 1 ppm. Severe surface damage in miracidia was observed with a general loss of cilia that probably cause their immobility. Miracidia exposed 30 min to low concentration of plant extract (0.1 ppm) were less infective with 3.3% of prevalence compare to untreated with a prevalence of 44%. Conclusions Essential oil extracted from E. triquetrum and falcarinol must be considered as a promising product for the development of new interventions for schistosomiasis control and could proceed to be tested on Phase II according to the WHO requirements.

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Schistosomes, snails and climate change: Current trends and future expectations

Cited by 83 publications

References 67 publications

Environmental DNA for improved detection and environmental surveillance of schistosomiasis

Environmental DNA for improved detection and environmental surveillance of schistosomiasis

Snail-Related Contributions from the Schistosomiasis Consortium for Operational Research and Evaluation Program Including Xenomonitoring, Focal Mollusciciding, Biological Control, and Modeling

Molluscicidal and parasiticidal activities of Eryngium triquetrum essential oil on Schistosoma mansoni and its intermediate snail host Biomphalaria glabrata, a double impact

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