Legionnaires Disease incidence has risen in the Netherlands in recent years. For the majority of the cases, the source of infection is never identified. Two Dutch wastewater treatment plants (WWTPs) ...have previously been identified as source of outbreaks of Legionnaires Disease (LD) among local residents. The objective of this study is to examine if LD patients in the Netherlands are more exposed to aerosols originating from WWTPs than controls.
An atmospheric dispersion model was used to generate nationwide exposure maps of aerosols from 776 WWTPs in the Netherlands. Municipal sewage treatment plants and industrial WWTPs were both included. Exposure of LD cases and controls at the residential address was compared, in a matched case-control design using a conditional logistic regression. Cases were notified LD cases with onset of disease in the period 2013–2018 in the Netherlands (n = 1604).
Aerosols dispersed over a large part of the Netherlands, but modelled concentrations are estimated to be elevated in close proximity to WWTPs. A statistically significant association was found between LD and the calculated annual average aerosol concentrations originating from WWTPs (odds-ratio: 1.32 (1.06–1.63)). This association remained significant when the two outbreak-related WWTPs were removed from the analysis (odds-ratio: 1.28 (1.03–1.58)).
LD cases were more exposed to aerosols from WWTPs than controls. This indicates that exposure to aerosols dispersed from WWTPs caused Legionnaires Disease in residents living near WWTPs in the period 2013–2018. In order to investigate which characteristics of WWTPs are associated with an increased LD risk, the WWTP database should be updated and more data is needed on the presence and survival of aerosolized Legionella bacteria to improve the Legionella dispersion modelling. Furthermore, it is recommended to further investigate how aerosol dispersion of WWTPs can effectively be reduced in order to reduce the potential health risk.
•Exposure to aerosols from WWTPs likely caused LD in people near WWTPs in 2013–2018.•Atmospheric dispersion from wastewater treatment plants (WWTPs) was modelled.•Nationwide exposure maps were made for aerosols from 776 WWTPs in the Netherlands.•Spatial distribution of Legionnaires' disease (LD) was compared to exposure maps.•LD cases were estimated to be more exposed to aerosols from WWTPs than controls.
In total 1216 vegetables obtained from Dutch stores during 2012 and 2013 were analysed to determine the prevalence of 3rd-generation cephalosporin (3GC) resistant bacteria on soil-grown fresh produce ...possibly consumed raw. Vegetables grown conventionally and organically, from Dutch as well as foreign origin were compared. Included were the following vegetable types; blanched celery (n=192), bunched carrots (n=190), butterhead lettuce (n=137), chicory (n=96), endive (n=188), iceberg lettuce (n=193) and radish (n=120). Overall, 3GC-resistant Enterobacteriaceae were detected on 5.2% of vegetables. Based on primary habitat and mechanism of 3GC-resistance, these bacteria could be divided into four groups: ESBL-producing faecal species (Escherichia coli, Enterobacter spp.), AmpC-producing faecal species (Citrobacter freundii, Enterobacter spp.), ESBL-producing environmental species (Pantoea spp., Rahnella aquatilis, Serratia fonticola), and AmpC-producing environmental species (Cedecca spp., Hafnia alvei, Pantoea spp., Serratia plymuthica), which were detected on 0.8%, 1.2%, 2.6% and 0.4% of the vegetables analysed, respectively. Contamination with faecal 3GC-resistant bacteria was most frequently observed in root and bulb vegetables (average prevalence 4.4%), and less frequently in stem vegetables (prevalence 1.6%) and leafy greens (average prevalence 0.6%). In Dutch stores, only four of the included vegetable types (blanched celery, bunched carrots, endive, iceberg lettuce) were available in all four possible variants: Dutch/conventional, Dutch/organic, foreign/conventional, foreign/organic. With respect to these vegetable types, no statistically significant difference was observed in prevalence of 3GC-resistant Enterobacteriaceae between country of origin or cultivation type (5.2%, 5.7%, 5.7% and 3.3%, respectively).
Vegetables consumed raw may be a source of dissemination of 3GC-resistant Enterobacteriaceae and their resistance genes to humans. The magnitude of the associated public health risk presumably depends on the types of bacteria that are ingested, i.e., faecal or environmental species, and may therefore be higher for root and bulb vegetables compared to leafy greens.
•Soil-grown fresh produce (n=1216) possibly consumed raw were investigated.•3GC-resistant Enterobacteriaceae detected on 5.2% of the studied vegetables.•ESBL- and AmpC-producing faecal as well environmental species were identified.•Faecal 3GC-resistant bacteria were most often found in root and bulb vegetables.•No difference in prevalence between country of origin or cultivation type.
In the Netherlands, safe and sufficient drinking water is provided to the general population by ten drinking water companies. To guarantee safe drinking water the World Health Organization (WHO) ...developed a Water Safety Plan (WSP), a Risk Assessment and a Risk Management (RA/RM) framework. The objective of the study was to identify legally required RA approaches, to document application of RA/RM activities at Dutch drinking water companies and to determine to what extent these RA/RM activities as a whole cover all the elements of the WHO WSP approach. This study could be of interest to both managers of large water utilities and decision makers.
The assessment was performed by means of a policy review and interviews with two to four staff members involved in RA/RM from all ten Dutch drinking water companies combined with a joint workshop. The drinking water companies are well aware of the potential hazards and risks that can influence the drinking water quality. To guarantee the supply of safe and sufficient drinking water, the Dutch drinking water sector uses six different legally required RA/RM approaches. This study shows that by using the six legally required RA/RM approaches, all WSP steps are covered. WSP entails a generic risk assessment for identifying all hazards and hazardous events from source to tap, whereas the six legally required RA/RM each focus on specific risks at an advanced level. Each risk assessment provides information on specific hazards and hazardous events covering a part of the water supply chain. These legal requirements are complemented with additional RA/RM activities at sector and water company level such as codes of practices and standard operating procedures. The outcomes of all RA/RM approaches combined provide information from source to tap. When using multiple RA/RM approaches, it is crucial to share and combine information derived from the different activities.
Numerous studies have reported quantitative data on viruses in surface waters generated using different methodologies. In the current study, the impact of the use of either cell culture-based or ...molecular-based methods in quantitative microbial risk assessment was assessed. Previously and newly generated data on the presence of infectious human enteroviruses (HEV) and enterovirus and parechovirus RNA were used to estimate distributions of virus concentrations in surface waters. Because techniques for the detection of infectious human parechoviruses (HPeV) in surface waters were not available, a ‘Parallelogram Approach’ was used to estimate their concentrations based on the ratio infectious HEV/HEV RNA. The obtained virus concentrations were then used to estimate the probability of exposure for children during recreation in such virus contaminated surface waters.
Human enterovirus cell culture/PCR ratios ranged from 2.3 × 10−3 to 0.28. This broad range of ratios indicates that care should be taken in assuming a fixed ratio for assessing the risk with PCR based virus concentrations.
The probabilities of exposure to both enteroviruses and parechoviruses were calculated, using our Parallelogram Approach for the calculation of infectious parechoviruses. For both viruses it was observed that the detection method significantly influenced the probability of exposure. Based on the calculated culture data, PCR data, and the ingestion volume, it was estimated that the mean probabilities of exposure, of recreating children, to surface water containing viruses were 0.087 (infectious enteroviruses), 0.71 (enterovirus particles), 0.28 (parechovirus particles) and 0.025 (calculated infectious parechoviruses) per recreation event. The mean probabilities of exposure of children recreating in surface water from which drinking water is produced to infectious enteroviruses were estimated for nine locations and varied between 1.5 × 10−4 – 0.09 per recreation event.
In this study, the use of the rotavirus dose response relationship as a surrogate was avoided. Instead, the probabilities of exposure were derived as a function of the distributions of the calculated doses. Our ‘Parallelogram Approach’ was used to estimate the unavailable infectious parechovirus concentrations using Monte Carlo simulations, and the exposure assessment carried out showed that virus concentrations present in surface waters could pose a health risk for children and other vulnerable populations.
•The infectious virus/viral genome ratio R of HEV varied from 2.3 × 10−3 to 0.28.•Using this ratio the mean infectious HPeV concentration was estimated as 0.91 PFU/L.•This enables the assessment of exposure to infectious HPeV of recreating children.•The 95% exposure probability was estimated as 0.13 per recreation event.•Thus recreation in these surface waters poses a substantial risk for public health.
During 2007–2010, over 4000 persons in The Netherlands contracted Q-fever, a zoonosis caused by the bacterium Coxiella burnetii. Goats and sheep are the main reservoir of C. burnetti and infected ...animals shed the bacterium with their urine, faeces and birth products. Human infections may occur through direct contact with infected animals, or through inhalation of contaminated dust particles or aerosols. Discharge of waste water from Q fever contaminated goat farms may result in the presence of C. burnetii in sewage water and aerosols at sewage water treatment plants (SWTPs) which may pose a health risk for workers or neighbouring residents. The objectives of this study were to determine the presence of C. burnetii at SWTPs and to optimize available detection methods. In March–July 2011, sewage influent and aeration tank samples from four SWTPs receiving discharge from Q fever positive goat farms were examined by using a multiplex real-time PCR detecting C. burnetii DNA by targeting IS1111 and com1 genes. Influent (44%; n=16/36) and active sludge (36%; n=13/36) samples were positive with low C. burnetii DNA content. Percentage positive samples per SWTP were 28–61%. Positive samples were most frequent in March 2011 and least frequent in May 2011. The presence of C. burnetii DNA in sewage water samples suggests that SWTPs receiving waste water from Q fever contaminated goat farms may contribute to the spread of C. burnetii to the environment. The low levels of C. burnetii DNA in sewage water during the decline of the Q fever outbreak in The Netherlands in 2011 indicate a low health risk for SWTP workers and residents.
Garden soils were investigated as reservoirs and potential sources of pathogenic Legionella bacteria. Legionella bacteria were detected in 22 of 177 garden soil samples (12%) by amoebal coculture. Of ...these 22 Legionella-positive soil samples, seven contained Legionella pneumophila Several other species were found, including the pathogenic Legionella longbeachae (4 gardens) and Legionella sainthelensi (9 gardens). The L. pneumophila isolates comprised 15 different sequence types (STs), and eight of these STs were previously isolated from patients according to the European Working Group for Legionella Infections (EWGLI) database. Six gardens that were found to be positive for L. pneumophila were resampled after several months, and in three gardens, L. pneumophila was again isolated. One of these gardens was resampled four times throughout the year and was found to be positive for L. pneumophila on all occasions.
Tracking the source of infection for sporadic cases of Legionnaires' disease (LD) has proven to be hard. L. pneumophila ST47, the sequence type that is most frequently isolated from LD patients in the Netherlands, is rarely found in potential environmental sources. As L. pneumophila ST47 was previously isolated from a garden soil sample during an outbreak investigation, garden soils were investigated as reservoirs and potential sources of pathogenic Legionella bacteria. The detection of viable, clinically relevant Legionella strains indicates that garden soil is a potential source of Legionella bacteria, and future research should assess the public health implication of the presence of L. pneumophila in garden soil.
Wastewater treatment plants (WWTPs), linking human fecal residues and the environment, are considered as hotspots for the spread of antimicrobial resistance (AMR). In order to evaluate the role of ...WWTPs and underlying operational parameters for the removal of AMR, the presence and removal efficiency of a selected set of 6 antimicrobial resistance genes (ARGs) and 2 mobile genetic elements (MGEs) was evaluated by means of qPCR in influent and effluent samples from 62 Dutch WWTPs. The role of possible factors impacting the concentrations of ARGs and MGEs in the influent and their removal was identified through statistical analysis. ARGs and the class I integron-integrase gene (intI1) were, on average, removed to a similar extent (1.76 log reduction) or better (+0.30–1.90 logs) than the total bacteria (measured as 16S rRNA gene). In contrast, broad-host-range plasmids (IncP-1) had a significantly increased (p < 0.001) relative abundance after treatment. The presence of healthcare institutions in the area served did only slightly increase the concentrations of ARGs or MGEs in influent. From the extended panel of operational parameters, rainfall, increasing the hydraulic load of the plant, most significantly (p < 0.05) affected the treatment efficiency by decreasing it on average −0.38 logs per time the flow exceeded the average daily flow. Our results suggest that overall, WWTP treatments do not favor the proliferation of the assessed resistance genes but might increase the relative abundance of broad-host-range plasmids of the IncP-1 type.
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•Sulfonamide (sul1) and macrolide (ermB) ARGs are predominant ARGs in the influent.•Healthcare institutions in the catchment didn't increase the influent's ARGs loads.•WWTP treatment reduced ARGs by 1.8–2.7 logs.•Relative abundance of IncP-1 plasmids was increased (p < 0.001) after WWTP treatment.•Rainfall increasing the WWTP hydraulic load significantly reduced the removal of ARGs.
Extreme rainfall events may cause pluvial flooding, increasing the transmission of several waterborne pathogens. However, the risk of experiencing clinically overt infections following exposure to ...pluvial floodwater is poorly estimated. A retrospective cross-sectional survey was performed to quantify the occurrence of self-reported gastrointestinal, influenza-like illness (ILI) and dermatological complaints, and the frequency of visits to the general practitioner (GP), during a 4-week observation period following pluvial flooding at seven locations in The Netherlands. Questionnaires were sent to 817 flooded households, 149 (17%) of which returned the questionnaire reporting information for 199 participants. Contact with floodwater was significantly associated with increased occurrence of gastrointestinal odds ratio (OR 4·44), ILI (OR 2·75) and dermatological (OR 6·67) complaints, and GP visits (OR 2·72). Having hand contact with floodwater was associated with gastrointestinal and dermatological complaints, whereas ILI complaints were associated with being engaged in post-flooding cleaning operations and having walked/cycled through floodwater. This study shows that floodwater-associated diseases occur in urban settings following extreme rainfall events in a high-income country. As pluvial floods are expected to escalate in the future due to global climate change, further research is warranted to determine the disease burden of pluvial flooding and to assess the effect of different interventions, including raising awareness among stakeholders.
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