published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

published_or_final_version / Public Health / Master / Master of Public Health

Background: Avian influenza is a serious infectious disease attracting great concerns of the world. It not only results in a huge economic loss but also poses a great threat to public health, and poultry production plays a major role of transmission as well as a locus of pathogen evolution, mutation and adaptation of avian influenza virus between wild birds and humans. Therefore, biosecurity measures along the poultry supply chains are important to prevent and control avian influenza. My objective was to summarize the past and present various measures against avian influenza in the industrial, commercial and backyard poultry production systems. Methods: A literature search was performed by PubMed, HKU Scholar Hub and Google. Based on the inclusion criterion and exclusion criterion, the relevant articles were selected with full text in English up to 11st, July 2013. Results: A total of 18 articles were found among the 474 potentially relevant articles. Among these articles, 17articlescame from PubMed and 1 article came from HKU Scholar Hub; 2 articles were closely related to industrial poultry production, 9 articles were closely related to commercial poultry production, 3 articles were closely related to village, rural or backyard poultry production and the rest 4 articles mixed the biosecurity measures in the different poultry production systems. These articles covered various biosecurity measures such as surveillance and monitoring, segregation, cleaning and disinfection, vaccination, training for workers, stamping out, controlling markets and poultry management in the developing and developed countries. Discussion: The common control measures are discussed and the biosecurity is aneffective way to prevent the avian influenza outbreaks in poultry and then to protect the health of all people. However, there were still limitations when implementing biosecurity. Due to local social, cultural, economic, psychological and political factors, it is difficult to prevent and control the avian influenza outbreaks in the poultry supply chains only by one single measure or individual. Therefore, some recommendations referring to cooperation of public and private sectors, comprehensiveness and specifity of measures, improving risk perception and education were discussed. / published_or_final_version / Public Health / Master / Master of Public Health

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / abstract / Microbiology / Master / Master of Philosophy

The Best PhD Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize / published_or_final_version / abstract / toc / Microbiology / Doctoral / Doctor of Philosophy

The S1 genome segment of avian reovirus is functionally tricistronic, encoding three independent protein products (named p10, p17 and ?C) from three sequential, partially overlapping open reading frames (ORFs). The dogma of translation initiation, the cap-dependent scanning model, suggests that ribosomes would normally only translate the 5?-proximal ORF. Four alternate mechanisms of translation initiation could account for translation of the downstream ?C ORF; an IRES element, reinitiation, ribosome shunting, and leaky scanning. The objective of my doctoral research was to investigate the translation initiation mechanisms that are operative on the S1 mRNA. Translation of the p10 and p17 ORFs was revealed to be coordinated via standard leaky scanning, while none of the known mechanisms of translation initiation could account for expression of the ?C ORF. Further investigation determined that two alternate cap-dependent mechanisms contribute to translation initiation at the ?C AUG codon. The first mechanism involves a modified version of enhanced leaky scanning. Although insertion of upstream elements known to impede scanning ribosomal subunits dramatically inhibited translation of the downstream ORF in the context of other mRNAs, the same elements only marginally reduced ?C translation. Specific features of the S1 mRNA therefore function to promote leaky scanning and translation of the ?C ORF. The inability to eliminate ?C expression beyond a threshold retention level of ~20-30%, despite the presence of eight upstream start codons that should eliminate leaky scanning, strongly suggests that ribosomes must also utilize a scanning-independent means to access the internal ?C start site. This mechanism for ?C translation initiation, which I termed ribosome handoff, allows ribosomes to bypass upstream elements, and requires a sequence-dependent translation enhancer element present within S1 nucleotides 366-392 that may function to mediate handoff via complementarity with 18S ribosomal RNA. Translation initiation at the ?C start site is therefore made possible by two alternative mechanisms, enhanced leaky scanning and ribosome handoff from the 5?-cap. The novelty of these two mechanisms highlights the complexity of the translation initiation process and the potential heterogeneity of cellular ribosomes, which raises the possibility that internal initiation may be far more common than currently appreciated.

<p>Avian Influenza (AI) is a contagious viral zoonotic disease with great public health implications and negative socioeconomic impact (WHO, 2006a). The highly pathogenic avian influenza (HPAI) infection is transmitted from birds to man mostly through contact with contaminated poultry and objects (INFOSAN, 2005), hence people who come in contact with birds such as live bird sellers (LBS) are the more vulnerable population (WHO, 2006a). Inadequate knowledge of AI health risks and poor practice of AI preventive measures amongst LBS increases the risk of spread of the infection in both humans and animals.The aim of this study was to describe and quantify the knowledge and practice of LBS with regards to avian influenza health risks and preventive activities in Agege, an urban area in Lagos State, Nigeria.</p>

Avian influenza H5N1 causes occasional but serious infections in humans and efforts to produce vaccines against this strain continue. Current influenza vaccines are prophylactic and utilize the two major antigens, hemagglutinin and neuraminidase. NP is an attractive alternative antigen because it is highly conserved across all influenza strains, has been shown to increase the rate of viral clearance, and potential therapeutic vaccines would elicit cytotoxic T lymophcyte responses in an infected person. The NP antigen from H5N1 was characterized using a variety of physiochemical methods to gain insights into both the biological and physical properties of the antigen which are important from a regulatory viewpoint when considering therapeutic vaccines. Results obtained to date show that NP is relatively unstable and indicate that the conformation of the H5N1 NP antigen is highly dependent upon purification procedure, buffer conditions, pH and the presence or absence of RNA. These factors will need to be clearly defined and taken into consideration when manufacturing and regulating NP vaccine preparations.

Thesis (Ph. D.)--University of Iowa, 2007. / Thesis supervisor: Gregory C. Gray. Includes bibliographical references (leaves 94-105).