Improving the current diagnostic strategy for beak and feather disease virus in parrots

[摘要] English: Beak and feather disease (BFD), caused by Beak and feather disease virus (BFDV) is a dermatological condition afflicting parrot species. It is becoming increasingly difficult to ignore not only the significant negative economic impact that the virus has on the parrot breeding industry but also the detrimental effect it has on the survival of the endemic Cape parrot (Poicephalus robustus). The virus, a member of the Circoviridae, is known to possess a non-enveloped, circular, single-stranded DNA genome. Two major open reading frames (ORFs) encode the replication associated protein (Rep) and the coat protein (CP). The study was set out to evaluate and improve the current diagnostic strategy for BFDV, with both molecular and serological techniques. The following objectives were attempted: 1. To evaluate polymerase chain reaction (PCR) and quantitative real-time polymerase chain reaction (qPCR) as diagnostic tools for BFDV. Detection of BFDV with conventional PCR is not always sensitive, especially in birds without clinical symptoms. Furthermore, genetic variance was suggested to have a detrimental effect on primer hybridisation. A real-time assay was designed to address these problems. It amplified a 115 bp fragment of ORF V1 and was able to quantify viral load. 2. To recombinantly express BFDV coat protein. A sustainable source of the main immunogen, coat protein, was needed for use in serological test development. Bacterial expression of BFDV CP was unsuccessful; however, BFDV CP from an alternative expression study was used as a serological diagnostic antigen. 3. To develop serological diagnostic tests for BFDV. A novel slide agglutination test was developed and will serve as an initial screening tool in serological diagnosis. Steps were made in the development of a competitive Enzyme Linked Immunosorbent Assay (ELISA) for a quantitative indication of immune response to BFDV. A significant proportion of asymptomatic BFDV infections exist. Using a combination approach of both molecular and serological tests increases the capacity to detect infections or exposure to virus. New techniques described should be used in conjunction with existing tests and should not completely replace conventional techniques for diagnosis of BFDV infection or detection of exposure to the virus.

[发布机构] University of the Free State