The influenza virus, a member of the Orthomyxoviridae family, causes regular, large-scale morbidity and mortality in birds and humans and significant human suffering and economic loss. The primary aim of this study was to develop a novel influenza vaccine. Vaccines are an essential tool for the control of influenza because they increase resistance to infection, prevent illness and death and help to limit virus transmission to other birds and mammals, including humans. By reducing the environmental contamination of influenza virus in global poultry stocks, the risk of a new pandemic virus being generated by the human-avian link is diminished. Marek’s Disease is a common lymphoproliferative disease of poultry that is readily controlled worldwide using the live attenuated vaccine, CVI988. The Marek’s Disease Virus (MDV) CVI988 viral genome, available as a Bacterial Artificial Chromosome (BAC), forms viable infectious viral particles when transfected into Chicken Embryo Fibroblast (CEF) cells. Using BAC mutagenesis, two non-essential genes in the MDV CVI988 BAC (UL41 and US10), were identified and replaced by the low pathogenic influenza haemagglutinin 10 (H10) gene. These live recombinant MDV-H10 vectors will allow simultaneous vaccination against both pathogens. In addition, the non-essential genes were also replaced with GFP creating MDV-GFP constructs. Both genes were expressed initially using a CMV promoter, although this disrupted the MDV CVI988 BAC; a second promoter, PGK-1, proved more successful. A third MDV gene (UL50) was deleted, but severe attenuation prevented the incorporation of H10 into this open reading frame. Future work to test the MDV-HA constructs in vivo will be carried out in collaboration with the Istituto Zooprofilattico Sperimentale delle Venezie in Italy. In addition, development of MDV constructs containing multiple HA genes (H10 and H5) linked by the 2A polyprotein can be developed with the goal of establishing heterosubtypic immunity.

Necrotic enteritis (NE) caused by Clostridium perfringens type A is an important bacterial enteric disease of global broiler production. However, the dynamic interactions of NE and its predisposing factors are not fully presented by current studies. By using the System Dynamics (SD) Model, the epidemiological changes in susceptible-infected-removed models of NE and avian coccidiosis and their interactions in one or multiple grow-out cycles was established; meanwhile, the growth performance was measured by the average weights of infected and non-infected populations at harvest were estimated. The SD model provided direct and persuasive outcomes of the epidemiology and ecology of NE compared with models using statistical methodology. With interventions on certain predisposing factors of management practices and medication, effects which decreased disease incidence and growth performance were observed; moreover, the leverage points obtained from interventions on certain management practices provided quantitative results which were applicable and useful for improving the broiler production.

Thesis (M.Sc. Agriculture (Animal Production)) -- University of Limpopo, 2019 / Poultry is a good source of animal protein for many households due to its affordability. However, it is prone to bacterial infections which can be passed on to consumers, hence chickens that are reared without constant health checks present a potential health threat to humans. The objective of the study was to identify the zoonotic bacterial pathogens in poultry feeds and water resources in Blouberg poultry value chain project. A total of 88 samples comprising of 14 feed samples, 14 water samples, 60 mouth and rectal swab samples were collected from the farms. The samples were screened for the presence of Escherichia coli, Salmonella spp. and Shigella spp. through selective cultivation. Only coliforms and the dominant isolates were identified as Escherichia coli, Klebsiella spp., and Enterobacter spp., Salmonella and Shigella spp. were not detected in all the samples. E. coli strains that were isolated from the water sources and mouth and rectal swabs of the chickens showed a significant resistance to gentamycin, neomycin, penicillin, streptomycin, tetracycline, erythromycin, nalidixic acid, ciprofloxacin and ampicillin (p<0.05). Klebsiella pneumoniae showed resistance to neomycin; penicillin; erythromycin (p<0.05) while K. oxytoca and E. absuriae showed similar antibiotic resistance profile as penicillin, erythromycin, nalidixic acid and ampicillin. E. coli and K. pneumonia are mostly implicated in poultry disease outbreaks and they are enteric pathogens in humans as well. The presence of pathogens in poultry presents a great risk of secondary infection in humans and this will lead to socio-economic problems for the affected communities. The information generated in this study will guide the relevant stakeholders who handle poultry feeds and water resources in following good management practices. 1 / National Research Foundation (NRF)