Avian Bornaviral Ganglioneuritis: Current Debates and Unanswered Questions

Abstract

Avian bornaviral ganglioneuritis, often referred to as parrot wasting disease, is associated with a newly discovered avian virus from the taxonomic family Bornaviridae. Research regarding the pathogenesis and treatment for this disease is ongoing, with implications for understanding other emerging human and nonhuman diseases, as well as the health and ecology of wildlife. At this time, numerous questions remain unanswered regarding the transmission of the disease, best practices for diagnostic sampling and testing, and whether currently used drug therapies are effective or harmful for afflicted birds. The pathogenesis of the disease also remains unclear with many birds showing resistance to the effects of the virus and being able to remain clinically unaffected for years, while other birds succumb to its effects. New research findings regarding avian bornaviral ganglioneuritis are discussed and important as yet unanswered questions are identified.

Surveillance of Parrot Bornavirus in Taiwan Captive Psittaciformes

“…The PaBV infection could cause PDD due to gastrointestinal crisis; however, neurological damage was more likely to appear in PaBV infection. Recently, it has become more appropriate to address this neurological crisis as avian ganglioneuritis (AGN) [48,49]. Probable mechanisms of PaBV leading to PDD/AGN were attributed to CD8+ T-cells, causing injury to neurons and ganglia recruiting CD4 T-cells, facilitating the antibody-mediated phagocytosis of axons [48].…”

Seeing beyond a Dilated Proventriculus: Diagnostic Tools for Proventricular Dilatation Disease in Psittacine Birds

“…Additional studies are needed to understand molecular aspects of tissue injury and lesion development. It has also been suggested that the term “avian ganglioneuritis (AG)” rather than PDD, should be used [ 15 ]. However, since the central nervous system can also be affected by lymphoplasmacytic infiltrates, this nomenclature does not reflect the complete spectrum of lesions that can be observed in PDD cases.…”

“…Several genotypes including parrot bornaviruses (PaBV)-1, 2, 3, 4, 5, 6 and 7, which belong to the species Psittaciform 1 and 2 orthobornavirus, have been identified in psittacine birds [12], and are summarized in Figure 1. Some studies have proposed the possibility of an autoimmune component to be involved in the development of PDD lesions and question if other causative agents can trigger these lesions [14,15]. To date, the only pathogens that have been extensively and consistently identified, through immunohistochemical and molecular methods in natural and experimental cases of PDD, are PaBVs.…”

“…In this review, we explore the main diagnostic tools that can be used for the diagnosis of PDD, with focus on ex situ conservation. Some studies have proposed the possibility of an autoimmune component to be involved in the development of PDD lesions and question if other causative agents can trigger these lesions [14,15]. To date, the only pathogens that have been extensively and consistently identified, through immunohistochemical and molecular methods in natural and experimental cases of PDD, are PaBVs.…”

Surveillance for Avian Bornavirus in Colorado and Wyoming, USA, Raptor Populations

“…Avian bornavirus (ABV) is a neurotropic virus, associated with avian bornaviral ganglioneuritis (ABG), a fatal disease characterized by neurologic and gastrointestinal dysfunction (Gregory et al 1994;Payne et al 2012;Tizard et al 2016;Meisle 2019;Boatright-Horowitz 2020). Although ABV is most prevalent in psittacine birds, and has been detected in at least 80 avian species; reports in raptors are limited (Gregory et al 1994;Hoppes et al 2013;Philadelpho et al 2014;Boatright-Horowitz 2020). One case in a Bald Eagle (Haliaeetus leucocephalus) and one case in a Peregrine Falcon (Falco peregrinus) have been reported, with both suspected to have become infected through predation of infected waterfowl (Payne et al 2012).…”