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1.  Solar disinfection: an approach for low-cost household water treatment technology in Southwestern Ethiopia 
Disinfection of contaminated water using solar radiation (SODIS) is known to inactivate bacteria. Its inactivation efficiency depends on local conditions where the disinfection is made. This study was aiming to test the efficiency of solar disinfection using different water parameters as low-cost household water treatment technology. Inactivation of microbes was tested using fecal coliform as test organism. The SODIS experiment was carried out at turbidity 2NTU, pH 7, and various water temperature (38.1°C, 41.8°C, 45.6°Cand 51.1°C) and solar intensities, using clear and black plastic bottles filled to different depths. The results show that the rate of microbial inactivation in relation to depth of water, turbidity, container type, intensity of light and color of container was statistically significant (p < 0.05). However, bottle placement, exposure and water pH were unrelated to microbial inactivation. Bacterial re-growth was not observed after solar disinfection. By adjusting the parameters, complete and irreversible fecal coliform inactivation was achieved within an exposure time of less than four hours in the areas where the solar irradiance is about 3.99 kW/m2 and above. Our results indicate that application of SODIS could play a significant role in the provision of safe water in rural communities of developing countries where there is ample sunshine, specifically in sub-Saharan African countries.
PMCID: PMC3895732  PMID: 24410979
Safe water supply; Water disinfection; Household water treatment; Solar radiation
2.  Physico-chemical and biological characterization of anopheline mosquito larval habitats (Diptera: Culicidae): implications for malaria control 
Parasites & Vectors  2013;6:320.
A fundamental understanding of the spatial distribution and ecology of mosquito larvae is essential for effective vector control intervention strategies. In this study, data-driven decision tree models, generalized linear models and ordination analysis were used to identify the most important biotic and abiotic factors that affect the occurrence and abundance of mosquito larvae in Southwest Ethiopia.
In total, 220 samples were taken at 180 sampling locations during the years 2010 and 2012. Sampling sites were characterized based on physical, chemical and biological attributes. The predictive performance of decision tree models was evaluated based on correctly classified instances (CCI), Cohen’s kappa statistic (κ) and the determination coefficient (R2). A conditional analysis was performed on the regression tree models to test the relation between key environmental and biological parameters and the abundance of mosquito larvae.
The decision tree model developed for anopheline larvae showed a good model performance (CCI = 84 ± 2%, and κ = 0.66 ± 0.04), indicating that the genus has clear habitat requirements. Anopheline mosquito larvae showed a widespread distribution and especially occurred in small human-made aquatic habitats. Water temperature, canopy cover, emergent vegetation cover, and presence of predators and competitors were found to be the main variables determining the abundance and distribution of anopheline larvae. In contrast, anopheline mosquito larvae were found to be less prominently present in permanent larval habitats. This could be attributed to the high abundance and diversity of natural predators and competitors suppressing the mosquito population densities.
The findings of this study suggest that targeting smaller human-made aquatic habitats could result in effective larval control of anopheline mosquitoes in the study area. Controlling the occurrence of mosquito larvae via drainage of permanent wetlands may not be a good management strategy as it negatively affects the occurrence and abundance of mosquito predators and competitors and promotes an increase in anopheline population densities.
PMCID: PMC4029358  PMID: 24499518
Decision trees; Generalized linear model; Macroinvertebrate predators; Mosquito control; Mosquito larvae
3.  High load of multi-drug resistant nosocomial neonatal pathogens carried by cockroaches in a neonatal intensive care unit at Tikur Anbessa specialized hospital, Addis Ababa, Ethiopia 
Cockroaches have been described as potential vectors for various pathogens for decades; although studies from neonatal intensive care units are scarce. This study assessed the vector potential of cockroaches (identified as Blatella germanica) in a neonatal intensive care unit setup in Tikur Anbessa Hospital, Addis Ababa, Ethiopia.
A total of 400 Blatella germanica roaches were aseptically collected for five consecutive months. Standard laboratory procedures were used to process the samples.
From the external and gut homogenates, Klebsiella oxytoca, Klebsiella pneumoniae, Citrobacter spp. Enterobacter cloacae, Citrobacter diversus, Pseudomonas aeruginosa, Providencia rettgeri, Klebsiella ozaenae, Enterobacter aeruginosa, Salmonella C1, Non Group A streptococcus, Staphylococcus aureus, Escherichia coli, Acinetobacter spp. and Shigella flexneri were isolated. Multi-drug resistance was seen in all organisms. Resistance to up to all the 12 antimicrobials tested was observed in different pathogens.
Cockroaches could play a vector role for nosocomial infections in a neonatal intensive care unit and environmental control measures of these vectors is required to reduce the risk of infection. A high level of drug resistance pattern of the isolated pathogens was demonstrated.
PMCID: PMC3436638  PMID: 22958880
Blatella germanica; Multi-drug resistant pathogens; Neonatal intensive care unit; Ethiopia
4.  Malaria and water resource development: the case of Gilgel-Gibe hydroelectric dam in Ethiopia 
Malaria Journal  2009;8:21.
Ethiopia plans to increase its electricity power supply by five-fold over the next five years to fulfill the needs of its people and support the economic growth based on large hydropower dams. Building large dams for hydropower generation may increase the transmission of malaria since they transform ecosystems and create new vector breeding habitats. The aim of this study was to assess the effects of Gilgel-Gibe hydroelectric dam in Ethiopia on malaria transmission and changing levels of prevalence in children.
A cross-sectional, community-based study was carried out between October and December 2005 in Jimma Zone, south-western Ethiopia, among children under 10 years of age living in three 'at-risk' villages (within 3 km from dam) and three 'control' villages (5 to 8 km from dam). The man-made Gilgel-Gibe dam is operating since 2004. Households with children less than 10 years of age were selected and children from the selected households were sampled from all the six villages. This included 1,081 children from 'at-risk' villages and 774 children from 'control' villages. Blood samples collected from children using finger prick were examined microscopically to determine malaria prevalence, density of parasitaemia and identify malarial parasite species.
Overall 1,855 children (905 girls and 950 boys) were surveyed. A total of 194 (10.5%) children were positive for malaria, of which, 117 (60.3%) for Plasmodium vivax, 76 (39.2%) for Plasmodium falciparum and one (0.5%) for both P. vivax and P. falciparum. A multivariate design-based analysis indicated that, while controlling for age, sex and time of data collection, children who resided in 'at-risk' villages close to the dam were more likely to have P. vivax infection than children who resided farther away (odds ratio (OR) = 1.63, 95% CI = 1.15, 2.32) and showed a higher OR to have P. falciparum infection than children who resided in 'control' villages, but this was not significant (OR = 2.40, 95% CI = 0.84, 6.88). A classification tree revealed insights in the importance of the dam as a risk factor for malaria. Assuming that the relationship between the dam and malaria is causal, 43% of the malaria occurring in children was due to living in close proximity to the dam.
This study indicates that children living in close proximity to a man-made reservoir in Ethiopia are at higher risk of malaria compared to those living farther away. It is recommended that sound prevention and control programme be designed and implemented around the reservoir to reduce the prevalence of malaria. In this respect, in localities near large dams, health impact assessment through periodic survey of potential vectors and periodic medical screening is warranted. Moreover, strategies to mitigate predicted negative health outcomes should be integral parts in the preparation, construction and operational phases of future water resource development and management projects.
PMCID: PMC2649153  PMID: 19178727

Results 1-4 (4)