Effects of water velocities on worm burdens of animals exposed to Schistosoma mansoni cercariae released under laboratory and field conditions

Radke, Myron G.; Ritchie, L. S.; Rowan, William

doi:10.1016/0014-4894(61)90039-x

Cited by 27 publications

(9 citation statements)

References 5 publications

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“…Compensating for this weak swimming ability, cercariae are chemokinetic and strongly attracted to molecules associated with human skin (34). They also actively swim to the surface (35), where they may be dispersed by currents (33, 36, 37); 10% of experimentally released Schistosoma japonicum cercariae were still infective to mice after traveling 100 m downstream at 0.182 m/s (38) and substantial worm burdens were acquired by mice experimentally exposed to S. mansoni cercariae even when cercariae were released 97.5 m (39) or 610 m (36) upstream from mice. The water contact sites where our study was based are small enough (average area, 1,607 m 2 ) that cercariae produced within these areas could conceivably traverse even the greatest dimension of the largest site (∼121 m), especially considering that cercariae have the capacity to efficiently detect and swim toward human bathers (40).…”

Section: Discussionmentioning

confidence: 99%

Precision mapping of snail habitat provides a powerful indicator of human schistosomiasis transmission

Wood

Sokolow

Jones

et al. 2019

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

108

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Recently, the World Health Organization recognized that efforts to interrupt schistosomiasis transmission through mass drug administration have been ineffective in some regions; one of their new recommended strategies for global schistosomiasis control emphasizes targeting the freshwater snails that transmit schistosome parasites. We sought to identify robust indicators that would enable precision targeting of these snails. At the site of the world’s largest recorded schistosomiasis epidemic—the Lower Senegal River Basin in Senegal—intensive sampling revealed positive relationships between intermediate host snails (abundance, density, and prevalence) and human urogenital schistosomiasis reinfection (prevalence and intensity in schoolchildren after drug administration). However, we also found that snail distributions were so patchy in space and time that obtaining useful data required effort that exceeds what is feasible in standard monitoring and control campaigns. Instead, we identified several environmental proxies that were more effective than snail variables for predicting human infection: the area covered by suitable snail habitat (i.e., floating, nonemergent vegetation), the percent cover by suitable snail habitat, and size of the water contact area. Unlike snail surveys, which require hundreds of person-hours per site to conduct, habitat coverage and site area can be quickly estimated with drone or satellite imagery. This, in turn, makes possible large-scale, high-resolution estimation of human urogenital schistosomiasis risk to support targeting of both mass drug administration and snail control efforts.

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Section: Discussionmentioning

confidence: 99%

Precision mapping of snail habitat provides a powerful indicator of human schistosomiasis transmission

Wood

Sokolow

Jones

et al. 2019

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

108

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“…Such environmental differences would produce variations in water temperature, turbulence, oxygen tension, and host availability, even though the stations were only 150 m apart, and this might have a dramatic effect on the incidence of infections. As a case in point, variations in water velocity radically influence the ultimate worm burdens of animals exposed to Schistosoma mansoni cercariae (Radke et al 1961). The marked difference in the incidence of infection within the same water body emphasises the care which must be exercised when sampling host populations to ensure valid results.…”

Section: Discussionmentioning

confidence: 98%

Suppression of egg production inPotamopyrgus antipodarum(Gastropoda: Hydrobiidae) by larval trematodes

McArthur

Featherston

1976

New Zealand Journal of Zoology

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“…They are highly susceptible to environmental stressors, including desiccation, turbulence in the water column, water temperature, aquatic chemistry and light. 2,[35][36][37][38][39] Water temperature and flow are key determinants of cercarial viability and thus C k (t) is dependent on the infected snail population as modified by these environmental factors:…”

Section: Modelling Cercariae-environment Interactionsmentioning

confidence: 99%

Modelling Environmentally-Mediated Infectious Diseases of Humans: Transmission Dynamics of Schistosomiasis in China

Remais

2010

Advances in Experimental Medicine and Biology

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M acroparasites of humans are sensitive to a variety of environmental variables, including temperature, rainfall and hydrology, yet current comprehension of these relationships is limited. Given the incomplete mechanistic understanding of environment-disease interactions, mathematical models that describe them have seldom included the effects of time-varying environmental processes on transmission dynamics and where they have been included, simple generic, periodic functions are usually used. Few examples exist where seasonal forcing functions describe the actual processes underlying the environmental drivers of disease dynamics. Transmission of human schistosomes, which involves multiple environmental stages, offers a model for applying our understanding of the environmental determinants of the viability, longevity, infectivity and mobility of these stages to controlling disease in diverse environments.Here, a mathematical model of schistosomiasis transmission is presented which incorporates the effects of environmental variables on transmission. Model dynamics are explored and several key extensions to the model are proposed.Modelling Parasite Transmission and Control, edited by Edwin Michael and Robert C. Spear.

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Effects of water velocities on worm burdens of animals exposed to Schistosoma mansoni cercariae released under laboratory and field conditions

Cited by 27 publications

References 5 publications

Precision mapping of snail habitat provides a powerful indicator of human schistosomiasis transmission

Precision mapping of snail habitat provides a powerful indicator of human schistosomiasis transmission

Suppression of egg production inPotamopyrgus antipodarum(Gastropoda: Hydrobiidae) by larval trematodes

Modelling Environmentally-Mediated Infectious Diseases of Humans: Transmission Dynamics of Schistosomiasis in China

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