Faecal bacterial loads during flood events in Northwestern Mediterranean coastal rivers

Chu, Yajing; Salles, Christian; Tournoud, Marie-George; Got, Patrice; Troussellier, Marc; Rodier, Claire; Caro, Audrey

doi:10.1016/j.jhydrol.2011.05.047

Cited by 29 publications

(18 citation statements)

References 37 publications

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“…It is also consistent with the peak of the bacterial causal agent reported by Phetsouvanh et al [13]. Here the end of the epidemic may be driven either by host immunity [51] and/or by the exhaustion of bacterial stores due to the continuous rainfall flushing [31,78]. …”

Section: Discussionsupporting

confidence: 86%

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Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment

Boithias

Choisy

Souliyaseng³

et al. 2016

PLoS Negl Trop Dis

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BackgroundThe global burden of diarrhea is a leading cause of morbidity and mortality worldwide. In montane areas of South-East Asia such as northern Laos, recent changes in land use have induced increased runoff, soil erosion and in-stream suspended sediment loads, and potential pathogen dissemination. To our knowledge, few studies have related diarrhea incidences to catchment scale hydrological factors such as river discharge, and loads of suspended sediment and of Fecal Indicator Bacteria (FIB) such as Escherichia coli, together with sociological factors such as hygiene practices. We hypothesized that climate factors combined with human behavior control diarrhea incidence, either because higher rainfall, leading to higher stream discharges, suspended sediment loads and FIB counts, are associated with higher numbers of reported diarrhea cases during the rainy season, or because water shortage leads to the use of less safe water sources during the dry season. Using E. coli as a FIB, the objectives of this study were thus (1) to characterize the epidemiological dynamics of diarrhea in Northern Laos, and (2) to identify which hydro-meteorological and sociological risk factors were associated with diarrhea epidemics.MethodsConsidering two unconnected river catchments of 22 and 7,448 km2, respectively, we conducted a retrospective time series analysis of meteorological variables (rainfall, air temperature), hydrological variables (discharge, suspended sediments, FIB counts, water temperature), and the number of diarrheal disease cases reported at 6 health centers located in the 5 southern districts of the Luang Prabang Province, Lao PDR. We also examined the socio-demographic factors potentially affecting vulnerability to the effect of the climate factors, such as drinking water sources, hygiene habits, and recreational water exposure.ResultsUsing thus a mixed methods approach, we found E. coli to be present all year long (100–1,000 Most Probable Number or MPN 100 mL-1) indicating that fecal contamination is ubiquitous and constant. We found that populations switch their water supply from wells to surface water during drought periods, the latter of which appear to be at higher risk of bacterial contamination than municipal water fountains. We thus found that water shortage in the Luang Prabang area triggers diarrhea peaks during the dry and hot season and that rainfall and aquifer refill ends the epidemic during the wet season. The temporal trends of reported daily diarrhea cases were generally bimodal with hospital admissions peaking in February-March and later in May-July. Annual incidence rates were higher in more densely populated areas and mostly concerned the 0–4 age group and male patients.ConclusionsWe found that anthropogenic drivers, such as hygiene practices, were at least as important as environmental drivers in determining the seasonal pattern of a diarrhea epidemic. For diarrheal disease risk monitoring, discharge or groundwater level can be considered as relevant proxies. These variables should be mon...

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Section: Discussionsupporting

confidence: 86%

“…Some authors suggested that the end of the epidemic could be driven by host immunity [51] and/or by the exhaustion of bacterial stores due to the continuous rainfall flushing [31,78]. The latter was not clear in our data as the baseline of E .…”

Section: Discussionmentioning

confidence: 64%

Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment

Boithias

Choisy

Souliyaseng³

et al. 2016

PLoS Negl Trop Dis

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“…Periods of droughts followed by short intense rainfall can cause peaks of surface water contamination. River-bed sediments represent an important microorganisms reservoir in dry areas, like the Mediterranean, where long dry periods are interrupted by flashfloods, transporting most of them downstream, up to coastal waters [66]. In areas affected by increasing droughts, treated effluents from sewage plants might become a quantitatively important source of water influx into river and heavy rainfall events can pose a risk to human health because of the huge increase of pathogenic microrganisms concentrations in the river downstream sewage treatment plants.…”

Section: Droughtsmentioning

confidence: 99%

Impact of climate change on waterborne diseases

Funari

Manganelli

Sinisi

2012

Annali Dell'Istituto Superiore Di Sanità

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Abstract. Change in climate and water cycle will challenge water availability but it will also increase the exposure to unsafe water. Floods, droughts, heavy storms, changes in rain pattern, increase of temperature and sea level, they all show an increasing trend worldwide and will affect biological, physical and chemical components of water through different paths thus enhancing the risk of waterborne diseases. This paper is intended, through reviewing the available literature, to highlight environmental changes and critical situations caused by floods, drought and warmer temperature that will lead to an increase of exposure to water related pathogens, chemical hazards and cyanotoxins. The final aim is provide knowledge-based elements for more focused adaptation measures.Key words: climate change, waterborne diseases, microbial pathogens, chemical contaminants, toxic cyanobacteria.Riassunto (Effetto dei cambiamenti climatici sulle malattie trasmesse dall'acqua). I cambiamenti climatici e del ciclo idrologico metteranno a rischio la disponibilità d'acqua e aumenteranno l'esposizione ad acqua contaminata. Le alluvioni, le siccità, le grandi tempeste, le variazioni nella frequenza ed intensità delle piogge, il riscaldamento e l'aumento del livello del mare crescono in ogni parte del mondo e influenzeranno le caratteristiche biologiche e chimico-fisiche dell'acqua attraverso diversi meccanismi, con il conseguente aumento del rischio di malattie trasmesse dall'acqua. L'analisi della letteratura disponibile, presentata in questo articolo, evidenzia i cambiamenti ambientali e le situazioni critiche causate da alluvioni, siccità e crescente riscaldamento che causeranno un aumento di esposizione a patogeni, inquinanti chimici e cianotossine, legati all'acqua. Lo scopo è di fornire gli elementi scientifici di base per misure di adattamento mirate.Parole chiave: cambiamenti climatici, malattie trasmesse dall'acqua, microrganismi patogeni, contaminanti chimici, cianobatteri tossici.

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“…Many studies have shown the impact of rainfall on microbial water quality in coastal and estuarine areas. Contamination due to rainfall most often results from urban wastewater discharges or from nonpoint pollution sources in the watershed (Lipp et al 2001;Chigbu et al 2005;Jeng et al 2005;Coulliette and Noble 2008;Papastergiou et al 2009;Chu et al 2011;Conn et al 2012). Microbial contamination can also occur in dry weather conditions, in which faecal material from seabirds resting on shellfish farming structures is the likely main source (Levesque et al 2000;Wither et al 2005;Ogburn and White 2009;Derolez et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Impact of weather conditions on Escherichia coli accumulation in oysters of the Thau lagoon (the Mediterranean, France)

et al. 2012

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Aims: The Thau lagoon shellfish are regularly impacted by microbial pollution of faecal origin, which cause European health standards to be exceeded and closure of the shellfish harvest. The aims of this study were to investigate the impact of weather and hydrological conditions on Escherichia coli (E. coli) accumulation factor (AF) between water and oysters and to evaluate the relevance of the use of this ratio for the purpose of sanitary risk assessment. Methods and results: Water and oysters (Crassostrea gigas) were sampled simultaneously in situ during 18 months in periods of dry weather and after rainfall events. Shellfish sanitary thresholds were exceeded in both periods. The E. coli AFs measured after rainfall (median = 6) were lower than in dry weather (median = 32), suggesting different shellfish faecal contaminations were operating in this system process. Conclusion: The AFs we measured appeared to be relevant markers for generating sanitary risk assessments for Thau lagoon shellfish. Significance and impact of the study: The results of the study address the need to assess the relationship between water quality measures and shellfish flesh quality. This study will contribute to the elaboration of a management tool to guide local authorities in prioritizing the sources of pollution and in optimizing public investment in the watershed. IntroductionWith up to 13 000 tons of oysters (Crassostrea gigas) and 2500 tons of mussels (Mytilus galloprovincialis) marketed every year, the Thau lagoon is the main shellfish harvesting area in the Mediterranean. Filter-feeding bivalves, such as oysters, filter large volumes of water from their environment and are able to concentrate large numbers of particles, which include micro-organisms pathogenic to human consumers (Bernard 1989;Plusquellec et al. 1990). According to European sanitary rules, the Escherichia coli concentrations found in Thau shellfish correspond to a Class B area. As a result, shellfish must be depurated before they can be marketed. Because Thau lagoon shellfish regularly exceed current health standards, authorities periodically restrict the shellfish harvesting area and, in some cases, suspend production. Moreover, several enteric virus outbreaks due to Thau lagoon oysters occurred during winter gastroenteritis epidemics in the local population .Many studies have shown the impact of rainfall on microbial water quality in coastal and estuarine areas. Contamination due to rainfall most often results from urban wastewater discharges or from nonpoint pollution sources in the watershed (Lipp et al. 2001;Chigbu et al. 2005;Jeng et al. 2005;Coulliette and Noble 2008;Papastergiou et al. 2009;Chu et al. 2011;Conn et al. 2012). Microbial contamination can also occur in dry weather conditions, in which faecal material from seabirds resting on shellfish farming structures is the likely main source (Levesque et al. 2000;Wither et al. 2005;Ogburn and White 2009;Derolez et al. 2010).European regulations recommend monitoring coliform bacteria (e.g. E. coli...

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Faecal bacterial loads during flood events in Northwestern Mediterranean coastal rivers

Cited by 29 publications

References 37 publications

Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment

Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment

Impact of climate change on waterborne diseases

Impact of weather conditions on Escherichia coli accumulation in oysters of the Thau lagoon (the Mediterranean, France)

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