Detection of Shiga toxin-encoding genes in small community water supplies.

Shiga toxin (Stx), one of the most potent bacterial toxins known, can cause bloody diarrhea, hemolytic uremic syndrome, kidney failure and death. The aim of this pilot was to investigate the occurrence of Shiga toxin-encoding genes, stx (stx1 and stx2) from total coliform (TC) and E. coli positive samples from small community water systems. After aliquots for TC and E. coli analyses were removed, the remnant volume of the samples was enriched, following a protocol developed for this study. Fifty-two per cent of the samples tested by multiplex PCR were positive for the presence of the stx genes; this percentage was higher in raw water samples. The stx2 gene was more abundant. Testing larger volumes of the samples increase the sensitivity of our assay, providing an alternative protocol for the detection of Shiga toxin-producing E. coli (STEC) that might be missed by the TC assay. This study confirms the presence of Stx encoding genes in source and distributed water for all systems sampled and suggests STEC as a potential health risk in small systems.

Recommendations for dealing with waste contaminated with Ebola virus: a Hazard Analysis of Critical Control Points approach.

OBJECTIVE: To assess, within communities experiencing Ebola virus outbreaks, the risks associated with the disposal of human waste and to generate recommendations for mitigating such risks. METHODS: A team with expertise in the Hazard Analysis of Critical Control Points framework identified waste products from the care of individuals with Ebola virus disease and constructed, tested and confirmed flow diagrams showing the creation of such products. After listing potential hazards associated with each step in each flow diagram, the team conducted a hazard analysis, determined critical control points and made recommendations to mitigate the transmission risks at each control point. FINDINGS: The collection, transportation, cleaning and shared use of blood-soiled fomites and the shared use of latrines contaminated with blood or bloodied faeces appeared to be associated with particularly high levels of risk of Ebola virus transmission. More moderate levels of risk were associated with the collection and transportation of material contaminated with bodily fluids other than blood, shared use of latrines soiled with such fluids, the cleaning and shared use of fomites soiled with such fluids, and the contamination of the environment during the collection and transportation of blood-contaminated waste. CONCLUSION: The risk of the waste-related transmission of Ebola virus could be reduced by the use of full personal protective equipment, appropriate hand hygiene and an appropriate disinfectant after careful cleaning. Use of the Hazard Analysis of Critical Control Points framework could facilitate rapid responses to outbreaks of emerging infectious disease.

Cryptosporidium in small water systems in Puerto Rico: a pilot study.

A pilot study was undertaken to investigate the occurrence of Cryptosporidium in four very small drinking water systems supplying communities in rural Puerto Rico. Water samples (40 L) were collected and oocysts were concentrated by calcium carbonate flocculation, recovered by immunomagnetic separation and detected by immunofluorescence microscopy. Cryptosporidium oocysts were identified in all four systems. This is the first report of evidence of the potential public health risk from this chlorine-resistant pathogen in Puerto Rican small water systems. Further work is warranted to fully assess the health risks that Cryptosporidium and other protozoa pose to populations served by community-managed small drinking water systems.

Impact on diarrhoeal illness of a community educational intervention to improve drinking water quality in rural communities in Puerto Rico.

BACKGROUND: Waterborne disease is a major risk for small water supplies in rural settings. This study was done to assess the impact of an educational intervention designed to improve water quality and estimate the contribution of water to the incidence of diarrhoeal disease in poor rural communities in Puerto Rico a two-part study was undertaken. METHODS: An educational intervention was delivered to communities relying on community water supplies. This intervention consisted of student operators and administrators supervising and assisting community members who voluntarily "operate" these systems. These voluntary operators had no previous training and were principally concerned with seeing that some water was delivered. The quality of that water was not something they either understood or addressed. The impact of this intervention was measured through water sampling for standard bacteriological indicators and a frank pathogen. In addition, face-to-face epidemiological studies designed to determine the base-line occurrence of diarrhoeal disease in the communities were conducted. Some 15 months after the intervention a further epidemiological study was conducted in both the intervention communities and in control communities that had not received any intervention. RESULTS: Diarrhoeal illness rates over a four week period prior to the intervention were 3.5%. Salmonella was isolated from all of 5 distributed samples prior to intervention and from only 2 of 12 samples after the intervention. In the 15 months follow-up study, illness rates were lower in the intervention compared to control communities (2.5% vs 3.6%%) (RR = 0.70, 95%CI 0.43, 1.15), though this was not statistically significant. However, in the final Poisson regression model living in an intervention system (RR = 0.318; 95%CI 0.137 - 0.739) and owning a dog (RR = 0.597, 95%CI 0.145 - 0.962) was negatively associated with illness. Whilst size of system (RR = 1.006, 95%CI 1.001 - 1.010) and reporting problems with sewage system (RR = 2.973, 95%CI 1.539 - 5.744) were positively associated with illness. CONCLUSIONS: Educational interventions directed both at identified individuals and the community in general in small communities with poor water quality is a way of giving communities the skills and knowledge to manage their own drinking water quality. This may also have important and sustainable health benefits, though further research preferably using a randomised control trial design is needed.

Spatial variability associated with shifting land use: water quality and sediment metals in La Parguera, Southwest Puerto Rico.

Development in southwest Puerto Rico, as in many areas of the Caribbean, is outpacing the ability of upland flora, salt flats, and mangroves to capture sediments and intercept and transform nutrients. A comparative study to examine the effects of development on near-shore water quality in La Parguera, Puerto Rico, was initiated in 1998. Total suspended solids were significantly higher in the vicinity of developing areas compared to reference areas. Chlorophyll-a measurements near of the wastewater treatment plant averaged two times the level of other areas. The overall average concentrations of copper, chromium, nickel, and zinc in sediments collected from salt flats exceeded values reported to cause impairment of biological systems. Marine sediments near more developed locations had the highest metal concentrations, suggesting a greater transport in this area. Natural resources are the primary attraction in this area; therefore, protection of near-shore resources should receive greater attention in land use planning.