Browsing by Author "Phiri, Bernard Joakim"
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- ItemEpidemiology of morbidity and mortality on smallholder dairy farms in Eastern and Southern Africa : a dissertation presented in partial fulfillment of the requirements for the degree of Master of Veterinary Studies in Epidemiology at Massey University(Massey University, 2008) Phiri, Bernard JoakimMorbidity and mortality are important causes of economic losses on dairy farms worldwide. In order to minimize these losses, the causes of morbidity and mortality and the associated risk factors need to be identified and appropriate control measures implemented. With the advent of globalization, more and more countries have sought to belong to regional groupings. One such grouping is the Common Market for Eastern and Southern Africa (COMESA). COMESA not only promotes trade but also encourages regional integration of research in areas such as agriculture. However, little is known is about the causes of morbidity and mortality and their risk factors on smallholder dairy farms in Eastern and Southern Africa (ESA) as a region. This thesis focuses, firstly, on the qualitative analysis of available scientific knowledge in order to identify the causes and associated risk factors for morbidity and mortality in ESA and, secondly, on the analysis of spatial patterns of excess mortality on smallholder dairy farms in Tanzania. A systematic review was conducted on the causes of morbidity and mortality on smallholder dairy farms in ESA. Mastitis, tick-borne diseases (TBDs), tick infestation and diarrhoea were the major causes of morbidity. TBDs, diarrhoea and trypanosomiasis were the major causes of mortality; however, a substantial number of mortalities with undiagnosed causes were also reported. This review also identified that the strong protective factors for mastitis were residual calf suckling and leaving one quarter un-milked; while teat lesions, tethering, washing teats only prior to milking, use of udder towel and poor body condition score were the main risk factors for mastitis. Zero-grazing was highly protective of TBDs while agro-ecological zone (AEZ), age and district were risk factors. Survival analysis using a Cox regression model fitted with a gamma-frailty term was employed to explore excess mortality on smallholder dairy farms in Tanga and Iringa regions of Tanzania. First- and second-order spatial patterns of farm frailty were analyzed. First-order patterns were recognizable in both regions, with large clusters around Tanga town and Iringa town respectively. The analysis did not provide evidence of second-order clustering. More intervention studies are recommended for the ESA region in order to better identify animal health constraints and their associated risk factors. Targeted research at aggregates of areas with high mortality would be the most cost-efficient way to identify the important risk factors.
- ItemEstimating the public health risk associated with drinking water in New Zealand : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Massey University, New Zealand(Massey University, 2015) Phiri, Bernard JoakimThis thesis is concerned with the application of both epidemiological and molecular tools to assess the drinking water safety in New Zealand. Compromised drinking water safety is commonly manifested as gastrointestinal illness. The studies in this thesis were motivated by the desire to nd ways of reducing the burden of such illness in the human population. Although the studies were conducted in the New Zealand setting the methodologies can be readily applied elsewhere. The rst study investigated the factors associated with the presence of microbes in raw water intended for public consumption. Random forest, an established non-parametric statistical method, was used to model data with possible complex interactions and identi ed variables that were predictive of the presence of microbes in raw drinking water. E. coli, which is widely used as a microbial contamination indicator in the water industry, was found to be a better predictor of the presence/absence of Campylobacter (bacteria) than protozoan microbes (Cryptosporidium and Giardia). This suggests that alternative methods of determining the presence/absence of pathogens in water should be developed. In the second study, the relationship between river ow and reports of cases of gastrointestinal illness was described using the distributed lag modelling approach. This revealed a positive relationship that peaked around 10 days after high ow. Further, the river ow-gastrointestinal illness relationship was stronger in small drinking distribution networks than in large ones. The small drinking water distribution networks could be targetted for facility upgrade in order to enhance their ability to deliver microbiologically safer drinking water. The third study utilised culture-dependent methods to assess the public health risk associated with drinking water supplied at outdoor recreation facilities | campgrounds. Water treatment using methods such as ultra violet and chemical treatment were found to be highly bene cial for the campgrounds to deliver drinking water that was microbiologically safe and compliant with water safety regulations. The pro les and functional factors of drinking water microbial communities are described in the fourth study. Techniques from the fast-growing eld of metagenomics were employed for this purpose. The capability of metagenomic techniques to detect multiple pathogens in a single assay was demonstrated. This has the potential to greatly enhance the speci city and sensitivity of microbial water quality testing.