Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (M.A.)--Georgia State University, 2007. / Title from file title page. Arla G. Bernstein, committee chair; Holley Wilkin, Leonard Teel, committee members. Electronic text (92 p. : ill. (some col.)) : digital, PDF file. Description based on contents viewed Oct. 17, 2007. Includes bibliographical references (p. 83-92).

Periodic introductions of influenza A viruses (IAVs) from wild birds contribute to emergence of novel strains that infect domestic poultry, lower mammals, and humans, but the mechanisms of emergence are unclear. The objectives of this dissertation research are to infer the genesis of two emerging IAVs, low pathogenic avian influenza (LPAI) H10N8 and highly pathogenic avian influenza (HPAI) H7N8 viruses, and to characterize the antigenic diversity and genetic evolution of contemporary H7 avian influenza viruses (AIVs) from North America. First, AIVs that are genetically close to the human H10N8 isolate were recovered at the live poultry market (LPM) visited by the first H10N8 patient. High seroprevalence of H10 virus was observed in ducks and chickens from five LPMs in the region. These findings suggested that LPM was the most probable source of human infection with the H10N8 virus, and this virus appeared to be present throughout the LPM system in the city. Second, the novel H7N8 virus most likely circulated among diving ducks in the Mississippi flyway during autumn 2015 and was subsequently introduced to Indiana turkey, in which it evolved from LPAI into HPAI. H4N8 IAVs from diving ducks possess a gene constellation comprising five H7N8–like gene segments. These findings suggest that viral gene constellations circulating among diving ducks could contribute towards the emergence of IAVs that can affect poultry. Diving ducks may serve as a unique reservoir, contributing to the maintenance, diversification, and transmission of IAVs in wild birds. Third, antigenic and genetic characterization of 93 H7 AIVs from North America showed limited antigenic diversity. Gradual accumulation of nucleotide and amino acid substitutions in the H7 gene of AIVs from wild and domestic birds caused a wide genetic diversity. These findings suggested that continuous genetic evolution has not led to significant antigenic diversity for contemporary H7 AIVs isolated from wild and domestic birds in North America. In summary, these findings not only improve our understanding of the ecology and evolution of IAVs but also provide information for formulation of effective disease prevention and control strategies.

M. Tech. (Department of Biotechnology, Faculty of Applied and Computer Science), Vaal University of Technology. / Influenza-A virus is a single stranded negative sense RNA virus that is a member of a Orthomyxoviridae group. The virus is diverse and consists of 16 haemagglutinin (H) and 9 neuraminidase (N) glycoproteins subtypes that form a serotype. Avian influenza virus (AIV) has been detected in more than 100 bird species from 26 different families, although Anseriformes and Charadriiformes are considered the natural hosts of the virus. A 12-month study was conducted at the African Pride Irene Country Club lodge in Pretoria where the prevalence of AIV was monitored in a community of wild birds. The African Pride Irene Country Club lodge houses a population of wild bird species such as Egyptian geese (Alopochen aegytptiaca), Yellow-billed duck (Anas undulata), Red knobbed coot (Fulica cristata), African sacred ibis (Threskiornis aethiopicus) and Hadeda ibis (Bostrycha hagedash). A total of 3674 faecal samples were collected over a period of 12 months and screened for AIV group using the Matrix gene (M-gene) real time reverse-transcriptase PCR (rRT-PCR). Positive samples were submitted for virus isolation in embryonated chicken eggs. In addition, the RNAs were screened using H5 and H7 subtype specific rRT-PCR and a conventional universal RCR assay that targets the HA gene was also used. Polymerase Chain Reaction (PCR) products were requenced using Sanger sequencing and the viral isolates were subjected to Next Generation sequencing (NGS). Twenty percent of the samples tested positive for the AIV group and four virus subtypes were identified. One virus isolate was identified through NGS as H3N6; two through conventional PCR and Sanger sequencing as H9Nx and H6Nx. Of the twenty percent samples that tested positive for AIV 98% were identified as H7Nx by subtype specific through rRT-PCR. The highest frequency of AIV positive samples was detected between the months of January and February 2017 (20%), with smaller peaks detected in february and March 2016 (0.3%). Lower peaks were also detected between the months July and November 2016 (0.1%), respectively. A high prevalence of AIV was detected in the late summer months with a frequency of 65% positive, although a low prevalence was also detected in the autumn (0.6%) winter (0.6%) and spring 0.08%). Thus, the study provides a valuable insight into the seasonal prevalence of AIV in a heterogeneous wild duck population in Gauteng Province.

published_or_final_version / abstract / toc / Paediatrics and Adolescent Medicine / Master / Master of Philosophy

published_or_final_version / abstract / Microbiology / Doctoral / Doctor of Philosophy

published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

This dissertation develops technology for microfluidic point-of-care (POC) immunoassay devices, divided into three papers, and explores the use of a quartz crystal microbalance for real time monitoring of blood coagulation in a fourth paper. The concept of POC testing has been well established around the world. With testing conveniently brought to the vicinity of the patient or testing site, results can be obtained in a much shorter time. There has been a global push in recent years to develop POC molecular diagnostics devices for resource-limited regions where well equipped centralized laboratories are not readily accessible. POC testing has applications in medical/veterinary diagnostics, environmental monitoring, as well as defense related testing. In the first paper, we demonstrated the use of latex immunoagglutination assays within a microfluidic chip to be an effective and sensitive method for detecting the bovine viral diarrhea virus. In the second paper the feasibility and general ease of integrating liquid core optical components onto a microfluidic lab-on-a-chip type device, for point-of-care AI diagnosis is demonstrated. In the third paper particle agglutination assays, utilizing light scattering measurements at a fixed angle from incident light delivery, for pathogen detection are explored in both Rayleigh and Mie scatter regimes through scatter intensity simulations and compared to experimental results. In the fourth paper a quartz crystal microbalance was used for real-time monitoring of fibrinogen cross-linking on three model biomaterial surfaces.

No description available.

Influenza A virus (AIV) has an extremely high rate of mutation. Frequent exchanges of gene segments between different AIV (reassortment) have been responsible for major pandemics in recent human history. The presence of a wild bird reservoir maintains the threat of incursion of AIV into domestic birds, humans and other animals. In this thesis, I addressed unanswered questions of how diverse AIV subtypes (classified according to antigenicity of the two surface proteins, haemagglutinin and neuraminidase) evolve and interact among different bird populations in different parts of the world, using Bayesian phylogenetic methods with large datasets of full genome sequences. Firstly, I explored the reassortment patterns of AIV internal segments among different subtypes by quantifying evolutionary parameters including reassortment rate, evolutionary rate and selective constraint in time-resolved Bayesian tree phylogenies. A major conclusion was that reassortment rate is negatively associated with selective constraint and that infection of wild rather than domestic birds was associated with a higher reassortment rate. Secondly, I described the spatial transmission pattern of AIV in China. Clustering of related viruses in particular geographic areas and economic zones was identified from the viral phylogeographic diffusion networks. The results indicated that Central China and the Pearl River Delta are two main sources of viral out flow; while the East Coast, especially the Yangtze River delta, is the major recipient area. Simultaneously, by applying a general linear model, the predictors that have the strongest impact on viral spatial diffusion were identified, including economic (agricultural) activity, climate, and ecology. Thirdly, I determined the genetic and phylogeographic origin of a recent H7N3 highly pathogenic avian influenza outbreak in Mexico. Location, subtype, avian host species and pathogenicity were modelled as discrete traits and jointly analysed using all eight viral gene segments. The results indicated that the outbreak AIV is a novel reassortant carried by wild waterfowl from different migration flyways in North America during the time period studied. Importantly, I concluded that Mexico, and Central America in general, might be a potential hotspot for AIV reassortment events, a possibility which to date has not attracted widespread attention. Overall, the work carried out in this thesis described the evolutionary dynamics of AIV from which important conclusions regarding its epidemiological impact in both Eurasia and North America can be drawn.