Johns Hopkins Center for Water and Health

Baltimore, MD, United States

Johns Hopkins Center for Water and Health

Baltimore, MD, United States
Time filter
Source Type

Lucy F.E.,Institute of Technology Sligo | Lucy F.E.,Carrick on Shannon Co. | Graczyk Z.,Johns Hopkins Center for Water and Health | Graczyk Z.,Institute of Technology Sligo | And 2 more authors.
Parasitology Research | Year: 2010

During summer months, samples of marine beach water were tested weekly for human waterborne pathogens in association with high and low bather numbers during weekends and weekdays, respectively. The numbers of bathers on weekends were significantly higher than on weekdays (P<0.001), and this was associated with a significant (P< 0.04) increase in water turbidity. The proportion of water samples containing Cryptosporidium parvum, Giardia duodenalis, and Enterocytozoon bieneusi was significantly higher (P<0.03) on weekends than on weekdays, and significantly (P<0.01) correlated with enterococci counts. The concentration of all three waterborne pathogens was significantly correlated with bather density (P<0.01). The study demonstrated that: (a) human pathogens were present in beach water on days deemed acceptable for bathing according to fecal bacterial standards; (b) enterococci count was a good indicator for the presence of Cryptosporidium, Giardia, and microsporidian spores in recreational marine beach water; (c) water should be tested for enterococci during times when bather numbers are high; (d) re-suspension of bottom sediments by bathers caused elevated levels of enterococci and waterborne parasites, thus bathers themselves can create a non-point source for water contamination; and (e) exposure to recreational bathing waters can play a role in epidemiology of microsporidiosis. In order to protect public health, it is recommended to: (a) prevent diapered children from entering beach water; (b) introduce bather number limits to recreational areas; (c) advise people with gastroenteritis to avoid bathing; and (d) use showers prior to and after bathing. © Springer-Verlag 2010.

Lucy F.E.,Institute of Technology Sligo | Connolly M.,Institute of Technology Sligo | Graczyk T.K.,Institute of Technology Sligo | Graczyk T.K.,Johns Hopkins Center for Water and Health | And 2 more authors.
Aquatic Invasions | Year: 2010

Zebra mussels (Dreissena polymorpha) are recognised biomonitors in determining the presence and viability of the human waterborne pathogens Cryptosporidium parvum, C. hominis, Giardia intestinalis and microsporidia in surface waters. This study investigated whether the size of zebra mussels is a significant factor in the concentration of protozoan Cryptosporidium oocysts, Giardia cysts and microsporidian spores. Zebra mussels were collected in Lough Arrow, a small Irish lake, which is utilized for drinking water abstraction and is subject to agricultural and human wastewater pollution drivers, both recognised risk factors for human waterborne pathogens. Zebra mussels were cleaned, divided into size (5 mm) interval classes based on their shell length and made up to 150 g samples (wet weight with shell). Combined fluorescence in situ hybridization (FISH) and immunofluorescent antibody (IFA) techniques were utilized as biomolecular techniques to assess the presence and concentration of the pathogens. PCR analysis provided source-tracking information on human and animal pollution sources. There was no significant relationship between the size of D. polymorpha and pathogen loads in similar sized samples, indicating that different sites in the same or different waterbody can be compared in terms of relative concentrations of human waterborne parasites irrespective of the zebra mussels' size. Cryptosporidium was the most abundant species, with lower counts of Giardia and the microsporidian Encephalitozoon hellem, respectively. Cryptosporidium oocysts and Giardia cysts were detected in zebra mussel samples at all three lake water abstraction points. A lake transect showed a decline in Cryptosporidium with increasing distance from a stream discharging sewage. Samples from agricultural sites indicated faecal inputs contaminated with these pathogens. Species identification implicated both human and animal faecal inputs to the lake from treated effluent, septic tanks, and agriculture. The research demonstrates the efficacy of zebra mussels as sentinels of water quality irrespective of their size. © 2010 The Author(s).

Cheng H.-W.A.,Institute of Technology Sligo | Lucy F.E.,Institute of Technology Sligo | Graczyk T.K.,Institute of Technology Sligo | Graczyk T.K.,Johns Hopkins Center for Water and Health | And 2 more authors.
Parasitology Research | Year: 2011

Municipal wastewater treatment plants play a vital role in reducing the microbial load of sewage before the end-products are discharged to surface waters (final effluent) or local environments (biosolids). This study was to investigate the presence of human-virulent microsporidian spores (Enterocytozoon bieneusi, Encephalitozoon intestinalis, and Encephalitozoon hellem) and enterococci during treatment processes at four Irish municipal secondary wastewater treatment plants (plants A-D). Microsporidian abundance was significantly related to seasonal increase in water temperature. Plant A had the least efficient removal of E. intestinalis spores (32%) in wastewater, with almost 100% removal at other plants both in April and July. Some negative removal efficiencies were obtained for E. bieneusi (at plants C and D, -100%) and for E. hellem (at plants A and D, -90% and -50%). In addition, a positive correlation was found between the levels of enterococci and E. bieneusi in July (r s=0.72, P<0.05). In terms of the dewatered biosolids, a median concentration as high as 32,000 spores/Kg of E. hellem was observed at plant D in July. Plant C sewage sludge contained the lowest microsporidian loadings (E. bieneusi; 450 spores/L and 1,000 spores/L in April and July, respectively). This study highlights the seasonal variation in concentrations of microsporidian spores in the incoming sewage. Spores in final effluents and dewatered biosolids can be the source of human-virulent microsporidian contamination to the local environment. This emphasizes a considerably high public health risk when sewage-derived biosolids are spread during summer months. This study also suggested enterococci as a potential indicator of the presence of microsporidian spores in wastewater, especially for E. bieneusi. © 2011 Springer-Verlag.

Gibson K.E.,University of Arkansas | Opryszko M.C.,Johns Hopkins Center for Water and Health | Schissler J.T.,Johns Hopkins Center for Water and Health | Guo Y.,Johns Hopkins Center for Water and Health | Schwab K.J.,Johns Hopkins Center for Water and Health
American Journal of Tropical Medicine and Hygiene | Year: 2011

An estimated 884 million people worldwide do not have access to an improved drinking water source, and the microbial quality of these sources is often unknown. In this study, a combined tangential flow, hollow fiber ultrafiltration (UF), and real-time PCR method was applied to large volume (100 L) groundwater (N = 4), surface water (N = 9), and finished (i.e., receiving treatment) drinking water (N = 6) samples for the evaluation of human enteric viruses and bacterial indicators. Human enteric viruses including norovirus GI and GII, adenovirus, and Polyomavirus were detected in five different samples including one groundwater, three surface water, and one drinking water sample. Total coliforms and Escherichia coli assessed for each sample before and after UF revealed a lack of correlation between bacterial indicators and the presence of human enteric viruses. Copyright © 2011 by The American Society of Tropical Medicine and Hygiene.

Gibson K.E.,Johns Hopkins Center for Water and Health | Gibson K.E.,University of Arkansas | Schwab K.J.,Johns Hopkins Center for Water and Health
Food and Environmental Virology | Year: 2011

We investigated the thermal inactivation profiles of murine norovirus (MNV), Hepatitis A virus (HAV), and feline calicivirus (FCV), which are surrogates for the study of human noroviruses. Thermal inactivation of MNV and FCV were evaluated at 37, 50, and 60°C and HAV at 37, 50, 60, and 70°C. All viral surrogates were relatively stable at 37°C. MNV and FCV decimal reduction times (D-values) at 50°C were statistically significantly different (P < 0.05) with MNV being more stable. Both surrogates had comparable, low D-values at 60°C. HAV had significantly higher (P < 0.05) D-values than both MNV and FCV at 50 and 60°C. Overall, the infectivity assay results indicate that HAV is resistant to thermal inactivation while MNV is moderately resistant and FCV is least resistant. © 2011 Springer Science + Business Media, LLC.

Nappier S.P.,Johns Hopkins Center for Water and Health | Graczyk T.K.,Johns Hopkins Center for Water and Health | Tamang L.,Johns Hopkins Center for Water and Health | Schwab K.J.,Johns Hopkins Center for Water and Health
Journal of Applied Microbiology | Year: 2010

Aims: To evaluate the bioaccumulation, retention and depuration rates of nine pathogens and surrogates when two oyster species were co-localized in tanks of seawater. Methods and Results: Crassostrea ariakensis (n = 52) and Crassostrea virginica (n = 52) were exposed to five virus types, two protozoan and two microsporidian species for 24 h. Oysters were then placed in depuration tanks, and subsets were removed and analysed for micro-organisms at weekly intervals. The odds of C. ariakensis oysters harbouring mouse norovirus-1 (MNV-1), human norovirus (NoV) or haepatitis A virus (HAV) were significantly greater than the odds of C. virginica oysters harbouring the same viruses (MNV-1 OR = 5·05, P = 0·03; NoV OR = 6·97, P = 0·01; HAV OR = 7·40, P < 0·001). Additionally, compared to C. virginica, C. ariakensis retained significantly higher numbers of transmissive stages of all protozoan and microsporidian species (P < 0·01). Crassostrea ariakensis oysters are also capable of retaining multiple human pathogens for at least 1 month. Conclusions: Crassostrea ariakensis oysters were statistically more likely to harbour enteropathogens and microbial indicators, compared to C. virginica. Individual C. ariakensis were also statistically more likely to retain multiple viruses, protozoa and microsporidia than C. virginica, highlighting the role the species may play in the transmission of multiple diseases. Significance and Impact of the Study: Nonnative Crassostrea ariakensis oysters are under review for their introduction into the Chesapeake Bay. The results of this study suggest that nonnative C. ariakensis oysters may present a serious public health threat to people consuming the oysters raw from contaminated sites. © 2009 The Society for Applied Microbiology.

Loading Johns Hopkins Center for Water and Health collaborators
Loading Johns Hopkins Center for Water and Health collaborators