Microbiological evaluation of water during the 2011 flood crisis in Thailand

Hazard identification and risk assessment of the organic, inorganic and microbial contaminants in the surface water after the high magnitude of flood event

The present work has been oriented to the qualitative and quantitative assessments of the aftermath effects of 2014 flood tragedy on the organic, inorganic and microbial contaminants in the floodwater, with a particular emphasis on their relative health risks and microbial infectious hazards to the flood-affected population, using average daily dose, hazard quotient, hazard index (HI), cancer risk (CR) and quantitative microbial risk assessment. Statistical comparison of the organic and inorganic contents was performed using the paired t-tests, while the predominant socio-demographic profiles and health attributes of the respondents to flood-induced health risks (HI) were verified by the chi-square test and binary logistic regression analysis. Among all, Fe, Cu, Pb, Ni, Zn, Cr, Cd, chlorpyrifos, diazinon, polycyclic aromatic hydrocarbons, estriol, 17α-ethinylestradiol, estrone, β-estradiol and bisphenol A were detected at the study area after flooding. The microbiological quality of the floodwater samples has been tracked positive for Escherichia coli, Salmonella typhimurium and Shigella flexneri, with the mean concentrations of 6500, 50 and 180 CFU/100 mL, respectively. Exposure and health risk assessments revealed that the overall HI value for organic and inorganic contaminants in the water samples was 1.19, exceeding the USEPA maximum limit of 1, after the flood incidence. The largest CR contributors were Ni, Cr and Cd, while the infection risks (P_inf,single) associated with the exposure of E. coli, Salmonella spp. and Shigella spp. were identified to be 3.1 × 10^-2, 1.2 × 10^-4 and 3.2 × 10^-5 for incidental scenario; and 8.3 × 10^-1, 3.9 × 10^-1 and 1.9 × 10^-1 for intentional scenario, respectively. The findings of these integrated tools are critically important to provide a more reliable quantitative assessment of human health hazards and microbial risks for different environmental settings, to safeguard water resource, and preservation of public health and the overall river ecosystem.

Leptospira in river and soil in a highly endemic area of Ecuador

BACKGROUND

Leptospira are shed into the environment via urine of infected animals. Rivers are thought to be an important risk factor for transmission to humans, though much is unknown about the types of environment or characteristics that favor survival. To address this, we screened for Leptospira DNA in two rivers in rural Ecuador where Leptospirosis is endemic.

RESULTS

We collected 112 longitudinal samples and recorded pH, temperature, river depth, precipitation, and dissolved oxygen. We also performed a series of three experiments designed to provide insight into Leptospira presence in the soil. In the first soil experiment, we characterized prevalence and co-occurrence of Leptospira with other bacterial taxa in the soil at dispersed sites along the rivers (n = 64). In the second soil experiment, we collected 24 river samples and 48 soil samples at three points along eight transects to compare the likelihood of finding Leptospira in the river and on the shore at different distances from the river. In a third experiment, we tested whether Leptospira presence is associated with soil moisture by collecting 25 soil samples from two different sites. In our river experiment, we found pathogenic Leptospira in only 4 (3.7%) of samples. In contrast, pathogenic Leptospira species were found in 22% of shore soil at dispersed sites, 16.7% of soil samples (compared to 4.2% of river samples) in the transects, and 40% of soil samples to test for associations with soil moisture.

CONCLUSIONS

Our data are limited to two sites in a highly endemic area, but the scarcity of Leptospira DNA in the river is not consistent with the widespread contention of the importance of river water for leptospirosis transmission. While Leptospira may be shed directly into the river, onto the shores, or washed into the river from more remote sites, massive dilution and limited persistence in rivers may reduce the environmental load and therefore, the epidemiological significance of such sources. It is also possible that transmission may occur more frequently on shores where people are liable to be barefoot. Molecular studies that further explore the role of rivers and water bodies in the epidemiology of leptospirosis are needed.

Microbiological Assessment of Tap Water Following the 2016 Louisiana Flooding

Floods are a prominent risk factor in the world of public health, as there is a risk of dispersal of harmful biological and chemical contaminants in floodwater. As climate change increases, the occurrence of natural disasters and risk of adverse health outcomes due to flash flooding also increases. Fecal indicator bacteria, such as Escherichia coli and Enterococci, are often encountered in contaminated floodwater and can cause gastrointestinal illnesses as well as a variety of infections. In August 2016, East Baton Rouge and surrounding parishes in Louisiana suffered heavy floods due to intense rainfall. No study of water quality during flooding has been conducted previously in Baton Rouge, Louisiana. Twenty-three pre-flush and post-flush water samples were collected immediately from accessible homes that had been affected by the floods in order to quantify concentrations of fecal indicator bacteria. These samples were analyzed for the presence of E. coli and Enterococci through both quantitative polymerase chain reaction (qPCR) and the IDEXX enzyme substrate method. The qPCR results indicated that 30% of the samples contained Enterococci and 61% of the samples contained E. coli, with the highest concentrations found in the pre-flush outdoor hose and the pre-flush kitchen tap. The IDEXX method yielded total coliforms in 65% of the samples, E. coli in 4%, and Enterococci in 35%, with the highest concentrations in the pre-flush outdoor faucet and the pre-flush post-filtration kitchen tap. Physical parameters including temperature, barometer pressure, dissolved oxygen, oxidation reduction potential, pH, conductivity, and salinity of these samples were also recorded. Of these parameters, conductivity and salinity were significant, suggesting they may positively influence E. coli and Enterococci growth.

Temporal Variability of Faecal Contamination from On-Site Sanitation Systems in the Groundwater of Northern Thailand

We investigated the impacts of on-site sanitation systems to local groundwater. In this year-long study, we monitored the response of faecal contamination levels to hydroclimatological factors including rainfall and groundwater table. Concentration of faecal indicators-E. coli (ESC), Enterococcus (ENT), nitrate-in thirteen pairs of shallow and deep wells were determined every 7-14 days. All samples from shallow wells were tested positive for faecal contamination (ESC and ENT > 1 MPN/100 mL) but concentration varies. A maximum of 24,000 MPN/100 mL were recorded in some shallow wells. Water from deep wells showed lower susceptibility to contamination with only 4 and 23% of samples tested positive for ESC and ENT, respectively. Concentrations of ESC and ENT were lower too, with a maximum of 5 MPN/100 mL and 28 MPN/100 mL, respectively. Fluctuation in contamination among the wells was described by four archetypal responses to hydroclimatological forcing: (i) flushing during the onset of wet season, (ii) dilution over the course of the wet season, (iii) concentration during the dry season, and (iv) synoptic response to storms. Previous studies attempting to link the prevalence of faecal/waterborne diseases and temporal factors (e.g., dry vs wet season) have produced differing outcomes. Our study may help explain the relevant hydrological mechanisms leading to these varying observations. Presently, most communities in Thailand have access to 'improved' sanitation systems. However, due to the unsustainable implementation of these systems, the otherwise viable drinking-water resources in the form of the abundant local groundwater has become a genuine health hazard.

The impact of flooding on aquatic ecosystem services

Flooding is a major disturbance that impacts aquatic ecosystems and the ecosystem services that they provide. Predicted increases in global flood risk due to land use change and water cycle intensification will likely only increase the frequency and severity of these impacts. Extreme flooding events can cause loss of life and significant destruction to property and infrastructure, effects that are easily recognized and frequently reported in the media. However, flooding also has many other effects on people through freshwater aquatic ecosystem services, which often go unrecognized because they are less evident and can be difficult to evaluate. Here, we identify the effects that small magnitude frequently occurring floods (< 10-year recurrence interval) and extreme floods (> 100-year recurrence interval) have on ten aquatic ecosystem services through a systematic literature review. We focused on ecosystem services considered by the Millennium Ecosystem Assessment including: (1) supporting services (primary production, soil formation), (2) regulating services (water regulation, water quality, disease regulation, climate regulation), (3) provisioning services (drinking water, food supply), and (4) cultural services (aesthetic value, recreation and tourism). The literature search resulted in 117 studies and each of the ten ecosystem services was represented by an average of 12 ± 4 studies. Extreme floods resulted in losses in almost every ecosystem service considered in this study. However, small floods had neutral or positive effects on half of the ecosystem services we considered. For example, small floods led to increases in primary production, water regulation, and recreation and tourism. Decision-making that preserves small floods while reducing the impacts of extreme floods can increase ecosystem service provision and minimize losses.

Critical Knowledge Gaps in Our Understanding of Environmental Cycling and Transmission of Leptospira spp

Exposure to soil or water contaminated with the urine of Leptospira-infected animals is the most common way in which humans contract leptospirosis. Entire populations can be at high risk of leptospirosis while working in inundated fields, when engaging in aquatic sports, or after periods of heavy rainfall. The risk of infection after contact with these environmental sources depends on the ability of Leptospira bacteria to survive, persist, and infect new hosts. Multiple variables such as soil and water pH, temperature, and even environmental microbial communities are likely to shape the environmental conditions needed by the pathogen to persist. Here we review what is known about the environmental phase of the infectious Leptospira transmission cycle and identify knowledge gaps that will serve as a guide for future research.

Hydrological connectivity and Burkholderia pseudomallei prevalence in wetland environments: investigating rice-farming community's risk of exposure to melioidosis in North-East Thailand

In our analysis of 136 water samples from wetland environments (rice paddies, natural wetland sites, man-made water bodies) in rural areas of North-East Thailand, Burkholderia pseudomallei was most prevalent in rice paddies (15 of the 30 positive sites). The high prevalence in the water of rice fields is indicative of the inherent vulnerability of farmers in rural agricultural areas in this area of Thailand and likely other locations in the tropics. Nearly all B. pseudomallei-positive sites were found within the vicinity of a large wetland associated with the Chi River, in the month of July 2014. Positive samples were found in water ranging in pH from 5.9 to 8.7, salinity ranging from 0.04 to 1.58 ppt, nitrate ranging from 0 to 10.8 ppm, and iron ranging from 0.003 to 1.519 ppm. Of these variables, only iron content was statistically higher in B. pseudomallei-positive versus B. pseudomallei-negative sites, suggesting that increasing concentrations of iron may encourage the growth of this bacterium, which is responsible for melioidosis. Our results, when combined with data from other published studies, support the notion that B. pseudomallei can exist in a wide range of environmental conditions. Thus, we argue that health safety education is a more appropriate means of addressing farmer vulnerability than chemical or physical alterations to fields at large scales. Further, it may be important to investigate melioidosis through transdisciplinary approaches that consider the complex social and ecological contexts in which the disease occurs.

Potential health implications of water resources depletion and sewage discharges in the Republic of Macedonia

Potential health implications of deficient sanitation infrastructure and reduced surface water flows due to climate change are examined in the case study of the Republic of Macedonia. Changes in surface water flows and wastewater discharges over the period 1955-2013 were analyzed to assess potential future surface water contamination trends. Simple model predictions indicated a decline in surface water hydrology over the last half century, which caused the surface waters in Macedonia to be frequently dominated by >50% of untreated sewage discharges. The surface water quality deterioration is further supported by an increasing trend in modeled biochemical oxygen demand trends, which correspond well with the scarce and intermittent water quality data that are available. Facilitated by the climate change trends, the increasing number of severe weather events is already triggering flooding of the sewage-dominated rivers into urban and non-urban areas. If efforts to develop a comprehensive sewage collection and treatment infrastructure are not implemented, such events have the potential to increase public health risks and cause epidemics, as in the 2015 case of a tularemia outbreak.

Altitude-scale variation in nitrogen-removal bacterial communities from municipal wastewater treatment plants distributed along a 3600-m altitudinal gradient in China

Microbial ecological information on the nitrogen removal processes in wastewater treatment plants (WWTPs) has been of considerable importance as a means for diagnosing the poor performance of nitrogen removal. In this study, the altitude-scale variations in the quantitative relationships and community structures of betaproteobacteria ammonia-oxidizing bacteria (βAOB) and nitrite-reducing bacteria containing the copper-containing nitrite reductase gene (nirK-NRB) and the cytochrome cd1-containing nitrite reductase gene (nirS-NRB) were investigated in 18 municipal WWTPs distributed along a 3660-masl altitude gradient in China. An altitude threshold associated with the proportions of NRB to total bacteria, NRB to βAOB and nirK-NRB to nirS-NRB was detected at approximately 1500m above sea level (masl). Compared with the stable proportions below 1500masl, the proportions exhibited a pronounced decreasing trend with increased altitude above 1500masl. Spearman correlation analysis indicated that the trend was significantly driven by altitude as well as multiple wastewater and operational variables. The community structure dissimilarity of βAOB, nirK-NRB and nirS-NRB showed significant and positive correlations with altitudinal distance between WWTPs. Redundancy analyses indicated that the variation in community structures above 1500masl were predominantly associated with wastewater, followed by operation and altitude. In summary, although the variations of nitrogen-removal bacterial community in WWTPs were driven dominantly by wastewater and operational variables, altitude was also an important variable influencing the quantitative relationships and community structures of nitrogen-removal bacteria in WWTPs particularly above 1500masl.

Impacts of a flash flood on drinking water quality: case study of areas most affected by the 2012 Beijing flood

In this study, we present a method for identifying sources of water pollution and their relative contributions in pollution disasters. The method uses a combination of principal component analysis and factor analysis. We carried out a case study in three rural villages close to Beijing after torrential rain on July 21, 2012. Nine water samples were analyzed for eight parameters, namely turbidity, total hardness, total dissolved solids, sulfates, chlorides, nitrates, total bacterial count, and total coliform groups. All of the samples showed different degrees of pollution, and most were unsuitable for drinking water as concentrations of various parameters exceeded recommended thresholds. Principal component analysis and factor analysis showed that two factors, the degree of mineralization and agricultural runoff, and flood entrainment, explained 82.50% of the total variance. The case study demonstrates that this method is useful for evaluating and interpreting large, complex water-quality data sets.

Estimating the microbiological risks associated with inland flood events: Bridging theory and models of pathogen transport

Flooding is known to facilitate infectious disease transmission, yet quantitative research on microbiological risks associated with floods has been limited. Pathogen fate and transport models provide a framework to examine interactions between landscape characteristics, hydrology, and waterborne disease risks, but have not been widely developed for flood conditions. We critically examine capabilities of current hydrological models to represent unusual flow paths, non-uniform flow depths, and unsteady flow velocities that accompany flooding. We investigate the theoretical linkages between hydrodynamic processes and spatio-temporally variable suspension and deposition of pathogens from soils and sediments; pathogen dispersion in flow; and concentrations of constituents influencing pathogen transport and persistence. Identifying gaps in knowledge and modeling practice, we propose a research agenda to strengthen microbial fate and transport modeling applied to inland floods: 1) development of models incorporating pathogen discharges from flooded sources (e.g., latrines), effects of transported constituents on pathogen persistence, and supply-limited pathogen transport; 2) studies assessing parameter identifiability and comparing model performance under varying degrees of process representation, in a range of settings; 3) development of remotely sensed datasets to support modeling of vulnerable, data-poor regions; and 4) collaboration between modelers and field-based researchers to expand the collection of useful data in situ.

An assessment of drinking-water quality post-Haiyan

INTRODUCTION

Access to safe drinking-water is one of the most important public health concerns in an emergency setting. This descriptive study reports on an assessment of water quality in drinking-water supply systems in areas affected by Typhoon Haiyan immediately following and 10 months after the typhoon.

METHODS

Water quality testing and risk assessments of the drinking-water systems were conducted three weeks and 10 months post-Haiyan. Portable test kits were used to determine the presence of Escherichia coli and the level of residual chlorine in water samples. The level of risk was fed back to the water operators for their action.

RESULTS

Of the 121 water samples collected three weeks post-Haiyan, 44% were contaminated, while 65% (244/373) of samples were found positive for E. coli 10 months post-Haiyan. For the three components of drinking-water systems - source, storage and distribution - the proportions of contaminated systems were 70%, 67% and 57%, respectively, 10 months after Haiyan.

DISCUSSION

Vulnerability to faecal contamination was attributed to weak water safety programmes in the drinking-water supply systems. Poor water quality can be prevented or reduced by developing and implementing a water safety plan for the systems. This, in turn, will help prevent waterborne disease outbreaks caused by contaminated water post-disaster.

Survey of Microbial Diversity in Flood Areas during Thailand 2011 Flood Crisis Using High-Throughput Tagged Amplicon Pyrosequencing

The Thailand flood crisis in 2011 was one of the largest recorded floods in modern history, causing enormous damage to the economy and ecological habitats of the country. In this study, bacterial and fungal diversity in sediments and waters collected from ten flood areas in Bangkok and its suburbs, covering residential and agricultural areas, were analyzed using high-throughput 454 pyrosequencing of 16S rRNA gene and internal transcribed spacer sequences. Analysis of microbial community showed differences in taxa distribution in water and sediment with variations in the diversity of saprophytic microbes and sulfate/nitrate reducers among sampling locations, suggesting differences in microbial activity in the habitats. Overall, Proteobacteria represented a major bacterial group in waters, while this group co-existed with Firmicutes, Bacteroidetes, and Actinobacteria in sediments. Anaeromyxobacter, Steroidobacter, and Geobacter were the dominant bacterial genera in sediments, while Sulfuricurvum, Thiovirga, and Hydrogenophaga predominated in waters. For fungi in sediments, Ascomycota, Glomeromycota, and Basidiomycota, particularly in genera Philipsia, Rozella, and Acaulospora, were most frequently detected. Chytridiomycota and Ascomycota were the major fungal phyla, and Rhizophlyctis and Mortierella were the most frequently detected fungal genera in water. Diversity of sulfate-reducing bacteria, related to odor problems, was further investigated using analysis of the dsrB gene which indicated the presence of sulfate-reducing bacteria of families Desulfobacteraceae, Desulfobulbaceae, Syntrobacteraceae, and Desulfoarculaceae in the flood sediments. The work provides an insight into the diversity and function of microbes related to biological processes in flood areas.

Development of a rapid, simple method for detecting Naegleria fowleri visually in water samples by loop-mediated isothermal amplification (LAMP)

Naegleria fowleri is the causative agent of the fatal disease primary amebic meningoencephalitis. Detection of N. fowleri using conventional culture and biochemical-based assays is time-consuming and laborious, while molecular techniques, such as PCR, require laboratory skills and expensive equipment. We developed and evaluated a novel loop-mediated isothermal amplification (LAMP) assay targeting the virulence-related gene for N. fowleri. Time to results is about 90 min and amplification products were easily detected visually using hydroxy naphthol blue. The LAMP was highly specific after testing against related microorganisms and able to detect one trophozoite, as determined with spiked water and cerebrospinal fluid samples. The assay was then evaluated with a set of 80 water samples collected during the flooding crisis in Thailand in 2011, and 30 natural water samples from border areas of northern, eastern, western, and southern Thailand. N. fowleri was detected in 13 and 10 samples using LAMP and PCR, respectively, with a Kappa coefficient of 0.855. To the best of our knowledge, this is the first report of a LAMP assay for N. fowleri. Due to its simplicity, speed, and high sensitivity, the LAMP method described here might be useful for quickly detecting and diagnosing N. fowleri in water and clinical samples, particularly in resource-poor settings.