Master of Science / Department of Diagnostic Medicine/Pathobiology / Steven S. Dritz / Cassandra K. Jones / Biological hazards in animal feed are a growing concern for the feed industry. Porcine epidemic diarrhea virus (PEDV) is the first viral pathogen confirmed to be transmissible in swine feed and feed ingredients. This led to investigations identifying the magnitude of transmissible risk PEDV imposes and strategies to mitigate infectivity in contaminated diets. The objective of the first experiment was to evaluate the minimum infectious dose of PEDV in virus-inoculated feed. Pigs became infected when PEDV concentrations at or above 5.6 × 10¹ 50% tissue culture infectious dose/g (TCID₅₀/g); corresponding feed cycle threshold (Ct) of 37 or below was utilized. Evaluation of a mitigation strategy for PEDV contaminated diets is also important since cross-contamination during feed manufacturing is possible. Therefore, the objective of the second experiment was to determine the effectiveness of feed batch sequencing as a method to minimize the risk of PEDV cross-contamination. This method was effective to reduce but not eliminate infectious PEDV carryover risk. Furthermore, feed that lacked detectible PEDV RNA as analyzed by quantitative real-time reverse transcription PCR assay (qPCR) was infectious. The third study was an observational study complementary to the previous experiment where the magnitude of virus contamination in the feed manufacturing facility was characterized during feed batch sequencing. Widespread contamination of the facility occurred and surfaces remained contaminated until chemically cleaned. The final experiment was conducted to assess PEDV RNA detection in feed and spray dried porcine plasma (SDPP) when analyzed by qPCR across 5 diagnostic laboratories. Overall, it appears qPCR PEDV RNA detection in feed and SDPP was precise as quantified by low coefficient of variation across laboratories, with the exception of one %CV from SDPP inoculated with low virus load from one laboratory. Although the magnitude of the Ct value difference was large in only 1 of 5 laboratories, comparisons of Ct values across laboratories should be interpreted cautiously. Finally, qPCR can be a useful surveillance tool for detection of PEDV RNA in non-clinical samples such as feed and SDPP.

South Africa currently faces multiple Cr(VI) contamination problems which are unsuccessfully remediated using available technologies. Cr(VI) is highly toxic, carcinogenic and mutagenic in nature and it is exclusively released through anthropogenic activities. A new treatment approach is proposed using locally isolated Cr(VI) reducing species of bacteria. This method is envisioned to be economical and ecologically friendly. Indigenous chromium(VI) reducing bacteria (CRBs) were isolated from a dried sludge consortium collected in the Brits Wastewater Treatment Plant, North-West Province (South Africa). Characterisation using 16S rRNA fingerprinting followed by taxonomic studies revealed a wide diversity of CRBs isolated under anaerobic conditions than under aerobic conditions. The consortium was determined to be predominantly gram-positive. The Cr(VI) reducing component of the culture was determined to be predominantly facultative, consisting predominantly of Bacillus sp., i.e. B. cereus, B. thuringiensis and B. mycoides. Batch experiments under both aerobic and anaerobic conditions showed a high Cr(VI) reducing performance under relatively high initial Cr(VI) concentrations. The reduction rate using this culture was 3 to 8 times higher than reduction rates reported in bacteria previously isolated and studied in North America and Europe. The culture performed best as a consortium with the different species operating cooperatively. The bacteria were acclimated to Cr(VI) toxicity through the long period of contact during the activated sludge treatment process at the source. A Monod like model was used to evaluate the rate of Cr(VI) reduction over a wide range of initial Cr(VI) concentrations. The model revealed that Cr(VI) reduction in the consortium culture followed quasi-first order kinetics with a Cr(VI) inhibitor term as a second exponential: C = C0 . exp [-p . exp (-q . C0 ) . t]. The parameter p and q for the semi-empirical first order model were statistically accurate with R2 values greater than 94% for all data ranges evaluated. Previous studies were not able to pick the variability of Monod coefficients, kmc and Kc, since at narrow ranges of initial Cr(VI) concentrations, the impact of the chromium toxicity variability was insignificant. This study demonstrates the potential of a biological approach using locally isolated Cr(VI) reducing bacteria to decontaminate Cr(VI) polluted sites in South Africa. / Dissertation (MSc)--University of Pretoria, 2009. / Chemical Engineering / unrestricted

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Since Actinomycetes have been isolated from finished public drinking water, it is believed that the organisms are unaffected by the chlorination and flocculation of water treatment plants and pass as spores through the filters into the general distribution system. For this reason it was deemed imperative to study the toxic effects of these organisms.

Submitted in fulfillment of the requirements for the Degree of Master of Technology: Biological Sciences at Technikon Natal, 2000. / Spice oils are known to exhibit antifungal activity and therefore have the potential to control mycotoxin production. There is a need in the food industry to find measures to control mycotoxins that are frequently associated with grains that form the staple diet of the majority of the population in South Africa. Clove, cinnamon, oregano, tumeric, eucalyptus, neem, aniseed, mace and nutmeg oils were tested to determine their inhibitory potential against growth of Aspergillus parasiticus and Fusarium moniliforme using the agar overlay technique. Varying concentrations of the spice oils, ranging from 0.1 ppm to 2.0 ppm, were incorporated into broth cultures of A. parasiticus and maize patty cultures ofF. moniliforme. Levels of production of aflatoxins and fumonisin were determined using standard thin layer chromatography and highpressure liquid chromatography methods. In addition, the active component of the spice oils were isolated, characterised and tested. The inhibitory potential of these compounds for field use was tested by incorporating clove oil, whole cloves and ground cloves in samp / M

Recent theories posit that cognitive factors explain the development and maintenance of contamination fears associated with obsessive compulsive disorder (OCD). Few studies to date have aimed to establish causality or temporal precedence for cognitions predicting OCD-relevant distress and avoidance. The current study used a prospective design to assess threat appraisals, personality traits, and obsessive compulsive symptoms in an unselected sample of university students and community members (N = 105) several days prior to a contamination behavioural approach task (BAT) in a public washroom. Results of the hierarchical regressions demonstrated that prospective danger appraisals significantly predicted both disgust and avoidance on the BAT, even when controlling for neuroticism, disgust sensitivity, and OCD symptoms. In contrast, looming germ spread appraisals and responsibility appraisals were not significant predictors of the BAT. Results from in vivo distress ratings and implicit reaction time data indicated that disgust is more strongly associated with contaminants compared with anxiety. The findings of this research suggest that psychological treatment for contamination concerns should include monitoring of disgust as a process and outcome variable in exposure paradigms, and focus on reappraisal of danger estimates related to disease in cognitive paradigms. / Arts, Faculty of / Psychology, Department of / Graduate

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The main scope of the work is to support a wider understanding of the achievements and limitations of economic analysis in historical contamination issues. The work describes how various schools of economics focus their study on environmental problems, specifically on Brownfields redevelopment. It presents the ideas of environmental economics, resource economics, free market environmentalism, institutional economics, political economy and ecological economics. The work includes a case study from the region of Ralsko in North Bohemia.

Land contamination remains a chronic threat to environmental integrity and human health, warranting scrutiny on the effectiveness of the domestic legal regime. South Africa has still to understand the full extent to which it will undermine the country's sustainable development goals and well-being of its population. Contaminated land impacts not only the environment, but it causes socio-economic impacts. In 2009, the National Environmental Management: Waste Act, 2008 (Act No. 59 of 2008) was enacted with a dedicated contaminated land regime (Part 8 of that Act). Given the importance of regulating contaminated land, a valuable analysis would be to determine whether Part 8 is legislatively adequately to enable the identification, management and rehabilitation of contaminated land. There is, however, a serious lack of information about the extent of land contamination in South Africa. This is evident from its the government's official reporting. There is also little information about the enforcement of the contaminated land regime itself and it is therefore difficult to measure its success. International studies have identified certain legislative best-practice elements for contaminated land regimes. These elements present a good yardstick against which to measure Part 8 of the Waste Act for purposes of determining whether it will enable the identification, management and rehabilitation of contaminated land. This study finds that while Part 8 contains some of the legislative best practices, it mostly falls short and various reforms are recommended.