Susanne Herbst

Mosquito nets in a rural area of Western Kenya: ownership, use and quality

BackgroundInsecticide-treated nets (ITNs) are regarded as one of the most effective strategies to prevent malaria in Africa. This study analyses the use and quality of nets owned by households in an area of high net coverage.MethodsA structured questionnaire on ownership and use of nets was administered to the households of individuals sampled from a local health centre in south Kisii district, Kenya. A physical inspection of all the nets in the households was done and their conditions recorded on spot check forms designed for that purpose.ResultsOf the 670 households surveyed, 95% owned at least one net. Only 59% of household residents slept under a net during the night prior to the survey. 77% of those who slept under a net used an insecticide-treated net (ITN) or long-lasting insecticide-treated nets (LLIN). Out of 1,627 nets in the survey households, 40% were deemed to be of poor quality because of holes. Compared to other age groups, children aged 5-14 years were most likely to have slept under nets of poor quality (odds ratio 1.41; p = 0.007).ConclusionsAlthough net ownership was high following increased delivery of ITNs, continuous promotion of effective maintenance and routine use is needed and efforts to replace damaged nets must be implemented.

Climate Change Impact Assessment of Food- and Waterborne Diseases

The PubMed and ScienceDirect bibliographic databases were searched for the period of 1998–2009 to evaluate the impact of climatic and environmental determinants on food- and waterborne diseases. The authors assessed 1,642 short and concise sentences (key facts), which were extracted from 722 relevant articles and stored in a climate change knowledge base. Key facts pertaining to temperature, precipitation, water, and food for 6 selected pathogens were scrutinized, evaluated, and compiled according to exposure pathways. These key facts (corresponding to approximately 50,000 words) were mapped to 275 terminology terms identified in the literature, which generated 6,341 connections. These relationships were plotted on semantic network maps to examine the interconnections between variables. The risk of campylobacteriosis is associated with mean weekly temperatures, although this link is shown more strongly in the literature relating to salmonellosis. Irregular and severe rain events are associated with Cryptosporidium sp. outbreaks, while noncholera Vibrio sp. displays increased growth rates in coastal waters during hot summers. In contrast, for Norovirus and Listeria sp. the association with climatic variables was relatively weak, but much stronger for food determinants. Electronic data mining to assess the impact of climate change on food- and waterborne diseases assured a methodical appraisal of the field. This climate change knowledge base can support national climate change vulnerability, impact, and adaptation assessments and facilitate the management of future threats from infectious diseases. In the light of diminishing resources for public health this approach can help balance different climate change adaptation options.

Spatial patterns of diarrhoeal illnesses with regard to water supply structures--a GIS analysis.

This paper presents an application of a geographical information system (GIS) in the field of research of drinking water epidemiology. A retrospective study regarding gastrointestinal infections was carried out in the Rhine-Berg District (North Rhine-Westphalia, Germany), which is characterised by different drinking water supply structures. The main objective was to examine the hypothesis that spatial variations of diarrhoeal illnesses may be linked with different drinking water sources (groundwater or surface water). We introduced a GIS for storing and analysing the wide range of data sets comprising features of the water supply structure and the epidemiological databases which constitute the basic elements of a surveillance-system for waterborne infectious diseases. GIS-techniques supported the generation of hypotheses regarding disease distribution and causation. The data bases which are routinely available turned out to be of sufficient quantity and quality for running a waterborne disease surveillance-system. Geo-statistical analysis revealed spatial variations in the incidence of diarrhoeal illnesses. Parameters depicting the water supply structures, especially the amount of drinking water produced from surface or groundwater, were correlated with the age-standardised incidence rates of gastrointestinal infections. The correlation models showed a trend of positive linkage between disease incidence and amount of groundwater. We found GIS-techniques extremely useful to carry out area-based correlation studies and to analyse the exposure of populations in drinking water epidemiology.

A comparison of efficiencies of microbiological pollution removal in six sewage treatment plants with different treatment systems

Six sewage treatment plants (STP) were investigated over a 12-month period in order to measure the microbiological load of untreated municipal wastewater and to evaluate the removal efficiencies of different treatment systems. The STP investigated can be classified into three categories: bigger plants with tertiary treatment, smaller plants with enhanced secondary treatment, and very small compact facilities. The plants studied had a considerable quantitative impact on the hydrology of the catchment area; consequently, it was anticipated that the microbiological load of the effluent would also be significant. Eighty samples were taken from the influent and effluent of the STP, regardless of weather conditions, and several bacterial and two parasitological parameters were analysed. The average microbiological reduction of each STP was dependent on its capacity and treatment procedures and varied between 1.9 and 3.5log10. Small compact facilities had a significantly lower removal efficiency (2.0+/-1log10) and discharged treated wastewater with a poorer microbiological quality compared to larger plants with tertiary treatment or with enhanced secondary treatment (2.8log10). Final sand filtration and extensive intermediate settling considerably improved the overall microbiological removal efficiency. During the study period, the microbiological water quality of the receiving water course was not significantly impaired by the discharge of any of the investigated plants; however, the compact facilities showed critical treatment deficiencies. In particular, the reduction of Giardia cysts was insufficient (<1.5log10) compared to that of the bigger plants (>3.0log10). In order to quantify the overall impact of microbiological loads on the receiving watercourse in this catchment area, it is also necessary to assess the pollution from combined sewer overflow basins and diffuse pollution. This will be considered in subsequent studies.

Knowledge Mapping for Climate Change and Food- and Waterborne Diseases

The authors extracted from the PubMed and ScienceDirect bibliographic databases all articles published between 1998 and 2009 that were relevant to climate change and food- and waterborne diseases. Any material within each article that provided information about a relevant pathogen and its relationship with climate and climate change was summarized as a key fact, entered into a relational knowledge base, and tagged with the terminology (predefined terms) used in the field. These terms were organized, quantified, and mapped according to predefined hierarchical categories. For noncholera Vibrio sp. and Cryptosporidium sp., data on climatic and environmental influences (52% and 49% of the total number of key facts, respectively) pertained to specific weather phenomena (as opposed to climate change phenomena) and environmental determinants, whereas information on the potential effects of food-related determinants that might be related to climate or climate change were virtually absent. This proportion was lower for the other pathogens studied (Campylobacter sp. 40%, Salmonella sp. 27%, Norovirus 25%, Listeria sp. 8%), but they all displayed a distinct concentration of information on general food- and water-related determinants or effects, albeit with little detail. Almost no information was available concerning the potential effects of changes in climatic variables on the pathogens evaluated, such as changes in air or water temperature, precipitation, humidity, UV radiation, wind, cloud coverage, sunshine hours, or seasonality. Frequency profiles revealed an abundance of data on weather and food-specific determinants, but also exposed extensive data deficiencies, particularly with regard to the potential effects of climate change on the pathogens evaluated. A reprioritization of public health research is warranted to ensure that funding is dedicated to explicitly studying the effects of changes in climate variables on food- and waterborne diseases.

GIS-based analysis of drinking-water supply structures: a module for microbial risk assessment.

Water-related infections constitute an important health impact world-wide. A set of tools serving for Microbial Risk Assessment (MRA) of waterborne diseases should comprise the entire drinking-water management system and take into account the Hazard Analysis and Critical Control Point (HACCP) concept which provides specific Critical Control Points (CCPs) reflecting each step of drinking-water provision. A Geographical Information System (GIS) study concerning water-supply structure (WSS) was conducted in the Rhein-Berg District (North Rhine-Westphalia, Germany). As a result, suitability of the existing water databases HYGRIS (hydrological basis geo-information system) and TEIS (drinking-water recording and information system) for the development of a WSS-GIS module could be demonstrated. Spatial patterns within the integrated raw and drinking-water data can easily be uncovered by GIS-specific options. The application of WSS-GIS allows a rapid visualization and analysis of drinking-water supply structure and offers huge advantages concerning microbial monitoring of raw and drinking water as well as recognition and investigation of incidents and outbreaks. Increasing requests regarding health protection and health reporting, demands for a better outbreak management and water-related health impacts of global climate change are major challenges of future water management to be tackled with methods including spatial analysis. GIS is assumed to be a very useful tool to meet these requirements.

Risk factor analysis of diarrhoeal diseases in the Aral Sea area (Khorezm, Uzbekistan)

In the Aral Sea basin, human activities have resulted in the severe degradation of water and soil, which is considered to cause serious human health problems. This study investigated the risk factors: water, sanitation and related hygiene issues for diarrhoeal disease in Khorezm province, Uzbekistan. The risk factors were studied using a combination of quantitative and qualitative methods including water quality monitoring, standardised questionnaires and spot checks. Multiple linear regression analysis revealed that visible contamination of drinking water during storage and the absence of anal cleansing materials were significantly associated with the number of diarrhoeal episodes per household. Overall, the findings of the study show that the domestic domain plays a major role with regard to faecal-oral disease transmission in Khorezm, Uzbekistan. Unhealthy excreta disposal habits and unsafe drinking water storage practices have to be urgently tackled in order to break the faecal-oral transmission route.

Water and Sanitation-Related Health Aspects in Khorezm, Uzbekistan

The severe man-made degradation of water and soil in the Aral Sea basin is considered to cause serious human health problems. Hence, the Center for Development (ZEF) in collaboration with the Institute for Hygiene and Public Health at the Bonn University Clinics, Germany, conducted a study on diarrhoeal diseases and its risk factors in the Khorezm Region between May 2003 and March 2004. In the study, we investigated the risk factors water, sanitation and hygiene for diarrhoeal disease by applying a combination of quantitative (exposure assessment, epidemiological data) and qualitative methods (standardized interviews, structured observations).