Psittacine beak and feather disease (PBFD) is a readily recognizable disease of
wild and captive psittacines in Australia but it is also a problem worldwide
wherever captive species are bred. The disease caused by beak and feather
disease virus (BFDV) is characterized by the progressive development of feather
dystrophy and loss. Although the occurrence of PBFD in South Africa has been
reported only recently, it is already rampant and threatens the extinction of the
endangered Cape parrot and black-cheeked lovebird.
Currently no vaccine for PBFD is commercially available but the loss of
approximately 10-20% of breeding stocks of psittacines annually in South Africa
alone is enough to realise the importance of one. Genetic and antigenic
differences in BFDV are significant aspects for production of a vaccine but the
lack of a culture system for BFDV has limited studies into its genetics,
antigenicity and pathogenicity. The objective of the study thus became to
establish techniques that could be used to investigate genetic and antigenic
differences that may be present in BFDV in South African psittacines.
Molecular investigations involved the testing dried blood samples for BFDV
nucleic acid using polymerase chain reaction (PCR). A region within the Rep
gene was amplified and digested with HaeIII to yield restriction length fragment
polymorphisms (RFLPs). Six RFLPs were identified, cloned, sequenced (UFS 1-
6) and phylogenetically analysed. BFDV was purified from body organs of PBFD-
affected birds by cesium chloride density gradient centrifugation and fractions
tested by PCR and haemagglutination (HA) assays. BFDV-specific antibodies
were raised in two rabbits by inoculation with purified BFDV in Freundâs
incomplete adjuvant and tested by haemagglutination inhibition (HI) assays and
an enzyme-linked immunosorbent assay (ELISA). HA and HI assays were attempted using erythrocytes from African grey parrots and Brown-headed
parrots. HI assays were also used to test parrot sera for the presence of
antibodies to BFDV.
UFS 1-6 were closely related to known BFDV isolates and UFS 1 may represent
a unique genotype in South Africa as it was separated from its closely related
isolates by a 90% bootstrap value. UFS 3, 4 and 5 isolated from budgerigars
belong to the budgerigar lineage as they clustered with isolate BG3-NZ. Together
with three previously identified genotypes, UFS 1 indicates the introduction of
BFDV into southern Africa on four separate occasions.
Purification of BFDV from organs was successful but yielded low titres possibly
because low quantities of virus were present in the organs or because little virus
was circulating in the bird upon its death. PCR and HA assays confirmed the
presence of BFDV in fractions; the two results correlated well.
HA and HI assays were successfully established using erythrocytes from African
grey parrots and Brown-headed parrots. Antibodies to BFDV were successfully
detected in sera of three parrots by the HI assay. However, the assay could not
detect non-psittacine raised antibodies (rabbit-raised) due to non-specific
reactions. BFDV-specific antibodies were successfully raised in rabbits and were
verified by the use of an ELISA.
The high level of genetic diversity observed in the study compels further
investigation into the genetics of BFDV as such levels of diversity may become a
limiting factor in the applicability of PCR as a diagnostic test. The entire diversity
of BFDV has not been studied and future work may lead to the identification of
more BFDV strains, an important factor in vaccine development. The rabbit-
raised antibodies together with the HA and HI assays and ELISA can be used to
study the antigenic differences that may be present in known BFDV isolates that
may also lead to the identification of more strains of the virus.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-09302005-090622 |
| Date | 30 September 2005 |
| Creators | Kondiah, Kulsum |
| Contributors | Dr J Albertyn, 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-09302005-090622/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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