Incidences of an Adenoviral infection have been recently reported in South African psittacine birds. These birds have been diagnosed by histopathology post-mortem. This Psittacine Adenovirus (PsAdV) has been reported as the second most deadly disease-causing virus in psittacine species with Psittacine Beak and Feather Disease Virus (PBFD) being the first. High mortalities with no symptoms have been observed amongst the birds. There is limited information on the distribution and antigenic characterisation of PsAdV in South Africa. This prompted the investigation into the isolation and characterisation of this PsAdV by virtue of molecular and conventional techniques.
Two birds suspected of being exposed to PsAdV were donated to the laboratory. Histopathological tests were already performed on these birds by a consulting veterinarian who found evidence supporting the Adenoviral infection. The livers of the parrots received were homogenised and DNA was then extracted from the suspension. These birds were from the same parrot breeding farm in the Free State region and their deaths occurred around September a year apart, inferring a seasonal occurrence of the infected birds.
A polymerase chain reaction (PCR) was established as a rapid test to confirm the Adenoviral infection amongst the birds received. A primer pair amplifying the hexon gene loop1 variable region (L1) located in two conserved pedestral regions was modified using an existing primer pair as this gene codes for the hexon protein where the group, subgroup and type specific antigenic determinants are located. PCR resulted in the expected amplicon size of ~587bp for all the samples tested with the use of a Fowl Adenovirus (FAdV) received from the Faculty of Veterinary Science, Onderstepoort (Pretoria) as a positive control. The positive DNA products were then subjected to restriction fragment length polymorphism (RFLP) in order to investigate differences in the restriction profiles. The suspected PsAdV samples provided a similar profile compared to the different one elicited by the fowl sample where only two bands were similar to the other profile with two extra unique bands observed. These samples were then ligated into the pGem-Teasy vector and the positive clones were selected and sent to Inqaba Biotech for sequencing.
The results where blasted on the NCBI GenBank Database and a high degree of similarity was found with the PsAdV sequences already on the database. Both the nucleotide and amino acid sequence alignments performed using DNAssist v2.2 showed a high homology with all the sequences. There were some differences observed and with the protein alignment the different amino acids observed were of the same group of amino acids. This suggested that the sequences were of the same genogroup. A neighbour-joining phylogenetic tree was constructed and this showed 4 major clusters where one of them represented the PsAdV sequences. The PsAdV sequences were separated from the other clusters by a 100% bootstrap value. The two minor branches within this cluster separating the UFS sequences from the reference PsAdV sequences suggested that the UFS samples could be different isolates.
Attempts to cultivate the virus in primary chicken embryonated liver cells and SPF embryonated eggs were successful and a cytopathic effect (CPE) typical of Adenoviruses was seen in the cells. With the SPF eggs definite differences were observed between the infected embryos and the negative control embryos. These were also typical of Adenoviruses, particularly of group I Aviadenoviruses (AAVs).
We propose that further studies be concentrated on the development of antibodies against this PsAdV in order to establish serological techniques so to be able to differentiate between different serogroups and isolates. We also propose the development of a vaccine against this psittacine Adenovirus so to put biosecurity measures in place.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-09042008-073823 |
| Date | 04 September 2008 |
| Creators | Mfenyana, Nandipha |
| Contributors | Prof RR Bragg |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-09042008-073823/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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