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Mycoplasma gallisepticum infection dynamics and vaccine protection in South African poultry
Thesis (PhD (Veterinary Science))--University of Pretoria, 2017.
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| Format: | Thesis |
| Language: | English |
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2026
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| _version_ | 1867613542934380544 |
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| access_status_str | Open Access |
| author2 | Abolnik, Celia |
| author_browse | Abolnik, Celia |
| author_facet | Abolnik, Celia |
| collection | Thesis |
| description | Thesis (PhD (Veterinary Science))--University of Pretoria, 2017. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/110175 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:37:48.825Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/110175 Mycoplasma gallisepticum infection dynamics and vaccine protection in South African poultry Abolnik, Celia u27565132@tuks.co.za Bwala, Dauda Garba Poultry Infection dynamics Mycoplasma galliesepticum South Africa Vaccine Protection Thesis (PhD (Veterinary Science))--University of Pretoria, 2017. Chronic respiratory disease, a form of mycoplasmosis caused by Mycoplasma gallisepticum (MG) is reported to be pervasive and prevalent in the South African poultry industry. However, limited and/or conflicting data exists on the strains of MG circulating within the industry, some of which were reported to be “novel” or different from MG from other regions. There were also unconfirmed field reports suggesting that ts-11 and 6/85 live-attenuated mycoplasmal vaccines have not being performing optimally against the circulating strains of MG. In view of the above, a study was conducted to determine the strains of MG circulating within the poultry industry and to assess the efficacy of the two commercially available vaccines against such strains in a multifactorial challenge model. In addition, the tissue distribution of MG was also determined using quantitative PCR as a means to assess vaccine efficacy, MG pathogenesis and the synergistic effect of IBV co-infection. The study sampling (passive and active) together with archived samples generated a total of 133 field isolates, three vaccine strains and one reference strain. Although quite a number of the field isolates were initially identified as MG based on the standard serological protocol (the use of hyperimmune serum for speciation) being implemented by the diagnostic laboratory, they were later found to be other species. Genomic DNAs from Mycoplasma isolates were sequenced using Ion Torrent and Ilumina MiSeq Next Generation Sequencing and 22 (16.54%) of them were identified as MG based on the sequence analysis of 16S rRNA gene. The phylogenetic analysis of the mgc2 and MGA_0319 (lp) genes, and the 16S-23S rRNA intergenic spacer region (IGSR) which provided a head-to-head comparison with an earlier study presented a good differentiation of the South African M. gallisepticum strains. Sequence analysis based on these three targets identified a clade of unique South African MG strains, displaying some genetic diversity. In addition, a number of South African isolates were also found be highly homologous to ts-11 and 6/85 vaccines which strongly suggests that these were vi vaccine strains re-isolated from the field. As expected, no F-strain gene sequences were detected in the sample set, because the F-strain vaccine was only registered for use in South Africa in 2015. In the second study, a multifactorial challenge model utilizing virulent MG strain ZA/MG B2159/13 and a QX-like infectious bronchitis virus (IBV) field strain was designed to assess the efficacy of the ts-11 and 6/85 vaccines. The multifactorial challenge model became necessary because under experimental conditions, overt clinical disease is often not induced by MG alone, and we wanted to mimic a common field situation where poultry flocks may be infected with mixed virulent pathogens. Results confirmed that vaccination with ts-11 and 6/85 vaccines were still efficacious in protecting birds against challenge with a local virulent field MG strain. The protection was however not absolute, as vaccination did not inhibit the development of tissue pathology. Furthermore, this study demonstrated that even though MG is a respiratory pathogen, it had little or no effect on tissue pathology and especially tracheal ciliary activity without IBV co-infection on the days that this was assessed. The assessment of tissue distribution of MG and IBV using qPCR and qRT-PCR demonstrated that even though MG and IBV are primarily respiratory pathogens, both can systemically spread to other organs such as liver, heart, cecal tonsils, kidneys, bursa of Fabricius and kidneys. Nevertheless, the respiratory organs (trachea, lungs and air sacs) were mostly affected. Vaccination with ts-11 delayed the colonisation and replication of challenge MG in some tissues, while in some instances ts-11 vaccination also accelerated or enhanced the elimination or clearance of the challenge MG in more organs than 6/85 vaccine. Production Animal Studies PhD (Veterinary Science) 2026-05-15T17:26:34Z 2026-05-15T17:26:34Z 17/07/11 2017 Thesis http://hdl.handle.net/2263/110175 en application/pdf |
| spellingShingle | Poultry Infection dynamics Mycoplasma galliesepticum South Africa Vaccine Protection Mycoplasma gallisepticum infection dynamics and vaccine protection in South African poultry |
| title | Mycoplasma gallisepticum infection dynamics and vaccine protection in South African poultry |
| title_full | Mycoplasma gallisepticum infection dynamics and vaccine protection in South African poultry |
| title_fullStr | Mycoplasma gallisepticum infection dynamics and vaccine protection in South African poultry |
| title_full_unstemmed | Mycoplasma gallisepticum infection dynamics and vaccine protection in South African poultry |
| title_short | Mycoplasma gallisepticum infection dynamics and vaccine protection in South African poultry |
| title_sort | mycoplasma gallisepticum infection dynamics and vaccine protection in south african poultry |
| topic | Poultry Infection dynamics Mycoplasma galliesepticum South Africa Vaccine Protection |
| url | http://hdl.handle.net/2263/110175 |