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

Perez-Saez, Javier; Mandé, Théophile; Zongo, Dramane; Rinaldo, Andrea

doi:10.1371/journal.pntd.0007938

Cited by 4 publications

(7 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Timed searches using a fine-meshed scoop net have been the standard procedure for snail host sampling over the past few decades (Sokolow et al 2018;Perez-Saez et al 2019). Actively searching through potential microhabitats results in an estimated abundance expressed as the number of snails caught per person per time unit.…”

Section: Data Collection Snail Sampling and Ancillary Data Collectionmentioning

confidence: 99%

“…Actively searching through potential microhabitats results in an estimated abundance expressed as the number of snails caught per person per time unit. Although highly valuable to capture seasonal variability within a single population, some possible concerns arise when comparing absolute abundances between different sites owing to the varying sampling efficiencies of individuals and different habitat typologies (Sokolow et al 2018;Perez-Saez et al 2019). Random quadrat sampling involves replicate, exhaustive sampling of a small, delineated surface area to estimate a population's absolute density.…”

Section: Data Collection Snail Sampling and Ancillary Data Collectionmentioning

confidence: 99%

“…Random quadrat sampling involves replicate, exhaustive sampling of a small, delineated surface area to estimate a population's absolute density. Despite enabling a direct comparison of the obtained abundances across different sites and individuals, this strategy is far more labour-intensive (Perez-Saez et al 2019).…”

Section: Data Collection Snail Sampling and Ancillary Data Collectionmentioning

confidence: 99%

“…Similar to earlier studies on the potential of citizen science in monitoring vectors for human pathogens (e.g., Porter et al 2019;Braz Sousa et al 2020), this pilot study was incentivized by the observation that the labour-and resource-intensive nature of vector monitoring by experts hampers multiyear large-scale observations and the setup of effective control programs. An additional lack of (inter) national standards further complicates the monitoring of freshwater snail hosts (Stothard et al 2017;Perez-Saez et al 2019;Maes et al 2021). Given the need for spatiotemporally dense observations, we designed a systematic sampling and classification strategy that can be executed by a selected group of trained volunteers.…”

Section: Beyond the Pilot Study: Broader Perspectives For Citizen Science And Vector Monitoring In Resource-limited Settingsmentioning

confidence: 99%

See 3 more Smart Citations

The Potential of Citizen-Driven Monitoring of Freshwater Snails in Schistosomiasis Research

Brees

Huyse

Tumusiime

et al. 2021

CSTP

View full text Add to dashboard Cite

Schistosomiasis is a tropical parasitic disease affecting more than 200 million people worldwide, predominantly in Africa. The World Health Organization recently highlighted the importance of targeted control of the freshwater snails acting as intermediate hosts for the parasites causing schistosomiasis. However, because of a shortage of trained experts and resources, detailed information on spatiotemporal snail distributions, which is needed for targeted control measures, is often missing. We explore the potential of citizen science to build these much-needed datasets through fine-grained, frequent snail sampling. We trained a network of 25 citizen scientists to weekly report on snail host abundances in 77 predefined water contact sites in and around Lake Albert (western Uganda). Snail abundance, together with marked GPS locations, water chemistry parameters, and photographs of the identified snails are recorded and submitted using the freely available mobile phone application KoBoToolbox. Trained researchers then engage in remote, semi-automatic validation of the submissions, after which there is an opportunity to provide targeted feedback to the citizen scientists. Five months after the operationalisation of the network, a total of 570 reports were submitted and personalized feedback was given, resulting in lasting improvements in subsequent reporting and snail genus identification. The preliminary results show the possibility of citizen science to independently obtain reliable data on the presence of schistosome snail hosts. We therefore argue that citizen-driven monitoring on a high spatiotemporal resolution could help to generate the much-needed data to support local targeted snail control measures in remote and/or resource-limited environments.

show abstract

Section: Data Collection Snail Sampling and Ancillary Data Collectionmentioning

confidence: 99%

Section: Data Collection Snail Sampling and Ancillary Data Collectionmentioning

confidence: 99%

Section: Data Collection Snail Sampling and Ancillary Data Collectionmentioning

confidence: 99%

Section: Beyond the Pilot Study: Broader Perspectives For Citizen Science And Vector Monitoring In Resource-limited Settingsmentioning

confidence: 99%

See 2 more Smart Citations

The Potential of Citizen-Driven Monitoring of Freshwater Snails in Schistosomiasis Research

Brees

Huyse

Tumusiime

et al. 2021

CSTP

View full text Add to dashboard Cite

show abstract

“…This provides a representation of the contact experience of a person standing in the water for 30 min. In addition, this method is as effective as quadrat methods in assessing snail population dynamics across long time periods [ 33 ]. Researchers searched for snails across the area of the pond, with special focus on microhabitats (submerged and floating vegetation, and other floating objects).…”

Section: Methodsmentioning

confidence: 99%

Spatio-temporal variability in transmission risk of human schistosomes and animal trematodes in a seasonally desiccating East African landscape

Starkloff,

Angelo,

Mahalila

et al. 2024

Proc. R. Soc. B.

View full text Add to dashboard Cite

Different populations of hosts and parasites experience distinct seasonality in environmental factors, depending on local-scale biotic and abiotic factors. This can lead to highly heterogeneous disease outcomes across host ranges. Variable seasonality characterizes urogenital schistosomiasis, a neglected tropical disease caused by parasitic trematodes ( Schistosoma haematobium ). Their intermediate hosts are aquatic Bulinus snails that are highly adapted to extreme rainfall seasonality, undergoing prolonged dormancy yearly. While Bulinus snails have a remarkable capacity for rebounding following dormancy, we investigated the extent to which parasite survival within snails is diminished. We conducted an investigation of seasonal snail schistosome dynamics in 109 ponds of variable ephemerality in Tanzania from August 2021 to July 2022. First, we found that ponds have two synchronized peaks of schistosome infection prevalence and observed cercariae, though of lower magnitude in the fully desiccating than non-desiccating ponds. Second, we evaluated total yearly schistosome prevalence across an ephemerality gradient, finding ponds with intermediate ephemerality to have the highest infection rates. We also investigated dynamics of non-schistosome trematodes, which lacked synonymity with schistosome patterns. We found peak schistosome transmission risk at intermediate pond ephemerality, thus the impacts of anticipated increases in landscape desiccation could result in increases or decreases in transmission risk with global change.

show abstract

Mapping of snail intermediate host habitat reveals variability in schistosome and nonschistosome trematode transmission in endemic settings

Angelo

Starkloff

Mahalila

et al. 2023

Preprint

View full text Add to dashboard Cite

Background There is growing recognition that mass drug administration must be complemented with environmental interventions to interrupt schistosomiasis transmission. Accurate mapping of snails and schistosome parasite distribution is critical to identify foci of human exposure and prioritize sites for interventions. Methodology We conducted longitudinal environmental surveys of snails and schistosomes in 467 waterbodies across 86 villages in northwestern Tanzania to describe spatial and temporal variation in snail and schistosome parasites presence and identify relevant underlying predictors. We conducted time constrained net sampling of Bulinus snails from vegetation, sediments, and floating objects and then examined all collected snails for patent infections. Principal findings A total of 43,272 Bulinus snails were collected across the three visits to each waterbody spanning November 2020 - August 2021, and we conducted statistical analyses on the latter two visits with more in-depth surveys (25,052 snails). We found patent schistosome infections in 0.87% of snails, 9.8% of waterbodies, and 31% of villages in all six districts. Variance decomposition indicated that variation among waterbodies was associated with variation in snail presence and the prevalence of schistosomes and nonschistosome parasites, whereas variation among villages and districts was not. Snail presence was highest in March-May a period of heavy rains, but otherwise not associated with waterbody characteristics. Waterbodies permitting cattle use had significantly higher prevalence of schistosomes than those permitting only human use. Nonschistosome parasites were more prevalent in June to September the dry season but were not associated with other waterbody characteristics. Waterbody permanence and distance to the nearest primary school were not associated with snails or parasites. Conclusions/significance This study revealed substantial variation in snails, schistosome and nonschistosome abundance at local (waterbody) scales, and it suggests links between community-driven water use decisions and schistosome transmission. The identification of local drivers of snail and schistosome abundance level and transmission factors at waterbody scale can complement studies across larger scales to shed light on transmission hotspots and guide the development of targeted interventions for schistosomiasis control.

show abstract

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

Cited by 4 publications

References 54 publications

The Potential of Citizen-Driven Monitoring of Freshwater Snails in Schistosomiasis Research

The Potential of Citizen-Driven Monitoring of Freshwater Snails in Schistosomiasis Research

Spatio-temporal variability in transmission risk of human schistosomes and animal trematodes in a seasonally desiccating East African landscape

Mapping of snail intermediate host habitat reveals variability in schistosome and nonschistosome trematode transmission in endemic settings

Contact Info

Product

Resources

About