The evidence for groundwater as a source of enteric illness in developing countries: A systematic review of the literature

Groundwater constitutes approximately 30% of freshwater globally and serves as a source of drinking water in many regions. Groundwater sources are subject to contamination with human pathogens (viruses, bacteria and protozoa) from a variety of sources that can cause diarrhea and contribute to the devastating global burden of this disease. To attempt to describe the extent of this public health concern in developing countries, a systematic review of the evidence for groundwater microbially-contaminated at its source as risk factor for enteric illness under endemic (non-outbreak) conditions in these countries was conducted. Epidemiologic studies published in English language journals between January 2000 and January 2011, and meeting certain other criteria, were selected, resulting in eleven studies reviewed. Data were extracted on microbes detected (and their concentrations if reported) and on associations measured between microbial quality of, or consumption of, groundwater and enteric illness; other relevant findings are also reported. In groundwater samples, several studies found bacterial indicators of fecal contamination (total coliforms, fecal coliforms, fecal streptococci, enterococci and E. coli), all in a wide range of concentrations. Rotavirus and a number of enteropathogenic bacteria and parasites were found in stool samples from study subjects who had consumed groundwater, but no concentrations were reported. Consumption of groundwater was associated with increased risk of diarrhea, with odds ratios ranging from 1.9 to 6.1. However, limitations of the selected studies, especially potential confounding factors, limited the conclusions that could be drawn from them. These results support the contention that microbial contamination of groundwater reservoirs—including with human enteropathogens and from a variety of sources—is a reality in developing countries. While microbially-contaminated groundwaters pose risk for diarrhea, other factors are also important, including water treatment, water storage practices, consumption of other water sources, water quantity and access to it, sanitation and hygiene, housing conditions, and socio-economic status. Further understanding of the interrelationships between, and the relative contributions to disease risk of, the various sources of microbial contamination of groundwater can guide the allocation of resources to interventions with the greatest public health benefit. Several recommendations for future research, and for practitioners and policymakers, are presented.^

Monitoreo de parásitos patógenos en afluentes agroindustriales

Las aguas residuales son potenciales portadoras de enteroparásitos patógenos para el hombre cuya dosis infectiva puede ser mínima y prolongado el tiempo de sobrevivencia de huevos y quistes en el ambiente. La reglamentación limita la presencia de huevos de helmintos y, hasta el año 2000, no proponía una técnica para su detección. Este trabajo se realizó para caracterizar parasitológicamente los efluentes procedentes de agroindustrias. La capacitación en la identificación microscópica demandó la confección de fichas que describen las características de huevos de helmintos. Se efectuaron ensayos con muestras de bodegas y aceiteras en los puntos detectados de contaminación. Los métodos fueron adaptados a las particularidades de los efluentes. Los resultados no señalaron presencia de helmintos; no obstante, se hallaron Cyclospora e Isospora, protozoarios que, por su alto poder infectivo, también constituyen un riesgo para el hombre. Sin embargo, no están contemplados por la legislación. Respecto a helmintos, es necesario un estudio comparativo de las técnicas de detección para efluentes agroindustriales, con el fin de establecer las que optimicen su recuperación. En cuanto a otras especies es preciso continuar investigando su presencia para evaluar la conveniencia de incorporarlas a la reglamentación.

Biomass of the main elements of the planktonic community in the Equatorial Pacific upwelling

Based on samples with a 140-liter bottles in the upwelling region of the equatorial Pacific, an analysis was made of vertical distribution of various members of the plankton community of organisms (small and large phytoplankton, bacteria, different groups of protozoans, small and large, mainly herbivorous and predatory, animals). There is a distinct vertical divergence between layers of dominance of groups with similar feeding habits against the background of uneven quantitative distribution. Contrariwise, there are masses of consumers in the layers of high concentration of their potential prey.