Microbial risk assessment of drinking water based on hydrodynamic modelling of pathogen concentrations in source water

Norovirus contamination of drinking water sources is an important cause of waterborne disease outbreaks. Knowledge on pathogen concentrations in source water is needed to assess the ability of a drinking water treatment plant (DWTP) to provide safe drinking water. However, pathogen enumeration in source water samples is often not sufficient to describe the source water quality. In this study, the norovirus concentrations were characterised at the contamination source, i.e. in sewage discharges. Then, the transport of norovirus within the water source (the river Gota alv in Sweden) under different loading conditions was simulated using a hydrodynamic model. Based on the estimated concentrations in source water, the required reduction of norovirus at the DWTP was calculated using quantitative microbial risk assessment (QMRA). The required reduction was compared with the estimated treatment performance at the DWTP. The average estimated concentration in source water varied between 4.8 x 10(2) and 7.5 x 10(3) genome equivalents L-1; and the average required reduction by treatment was between 7.6 and 8.8 Log(10). The treatment performance at the DWTP was estimated to be adequate to deal with all tested loading conditions, but was heavily dependent on chlorine disinfection, with the risk of poor reduction by conventional treatment and slow sand filtration. To our knowledge, this is the first article to employ discharge-based QMRA, combined with hydrodynamic modelling, in the context of drinking water. (C) 2015 Elsevier B.V. All rights reserved

Occurrence and removal efficiency of parasitic protozoa in Swedish wastewater treatment plants

Giardia intestinalis, Cryptosporidium spp., Entamoeba histolytica and Dientamoeba fragilis are parasitic protozoa and causative agents of gastroenteritis in humans. G. intestinalis and Cryptosporidium spp. in particular are the most common protozoa associated with waterborne outbreaks in high-income countries. Surveillance of protozoan prevalence in wastewater and evaluation of wastewater treatment removal efficiencies of protozoan pathogens is therefore imperative for assessment of human health risk. In this study, influent and effluent wastewater samples from three wastewater treatment plants in Sweden were collected over nearly one year and assessed for prevalence of parasitic protozoa. Quantitative real-time PCR using primers specific for the selected protozoa Cryptosporidium spp., G. intestinalis, E. histolytica, Entamoeba dispar and D. fragilis was used for protozoan DNA detection and assessment of wastewater treatment removal efficiencies. Occurrence of G. intestinalis, E. dispar and D. fragilis DNA was assessed in both influent (44, 30 and 39 out of 51 samples respectively) and effluent wastewater (14, 9 and 33 out of 51 samples respectively) in all three wastewater treatment plants. Mean removal efficiencies of G. intestinalis, E. dispar and D. fragilis DNA quantities, based on all three wastewater treatment plants studied varied between 67 and 87%, 37–75% and 20–34% respectively. Neither E. histolytica nor Cryptosporidium spp. were detected in any samples. Overall, higher quantities of protozoan DNA were observed from February to June 2012. The high prevalence of protozoa in influent wastewater indicates the need for continued monitoring of these pathogens in wastewater-associated aquatic environments to minimise the potential risk for human infection

UV radiation promotes melanoma dissemination mediated by the sequential reaction axis of cathepsins-TGF-beta 1-FAP-alpha

Background: Ultraviolet radiation (UVR) is the major risk factor for development of malignant melanoma. Fibroblast activation protein (FAP)-alpha is a serine protease expressed on the surface of activated fibroblasts, promoting tumour invasion through extracellular matrix (ECM) degradation. The signalling mechanism behind the upregulation of FAP-alpha is not yet completely revealed. Methods: Expression of FAP-alpha was analysed after UVR exposure in in vitro co-culture systems, gene expression arrays and artificial skin constructs. Cell migration and invasion was studied in relation to cathepsin activity and secretion of transforming growth factor (TGF)-beta 1. Results: Fibroblast activation protein-a expression was induced by UVR in melanocytes of human skin. The FAP-alpha expression was regulated by UVR-induced release of TGF-beta 1 and cathepsin inhibitors prevented such secretion. In melanoma cell culture models and in a xenograft tumour model of zebrafish embryos, FAP-alpha mediated ECM degradation and facilitated tumour cell dissemination. Conclusions: Our results provide evidence for a sequential reaction axis from UVR via cathepsins, TGF-beta 1 and FAP-alpha expression, promoting cancer cell dissemination and melanoma metastatic spread.Funding Agencies|Swedish Research Council; Welander-Finsen Foundation; Ostgotaregionens Cancer Foundation; Swedish Cancer Society; County Council of Ostergotland; Olle Engkvist Foundation</p