Tissue Distribution of Parrot Bornavirus 4 (PaBV-4) in Experimentally Infected Young and Adult Cockatiels (Nymphicus hollandicus)

Abstract

Proventricular dilatation disease (PDD) caused by parrot bornavirus (PaBV) infection is an often-fatal disease known to infect Psittaciformes. The impact of age at the time of PaBV infection on organ lesions and tissue distribution of virus antigen and RNA remains largely unclear. For this purpose, tissue sections of 11 cockatiels intravenously infected with PaBV-4 as adults or juveniles, respectively, were examined via histology, immunohistochemistry applying a phosphoprotein (P) antibody directed against the bornaviral phosphoprotein and in situ hybridisation to detect viral RNA in tissues. In both groups of adult- and juvenile-infected cockatiels, widespread tissue distribution of bornaviral antigen and RNA as well as histologic inflammatory lesions were demonstrated. The latter appeared more severe in the central nervous system in adults and in the proventriculus of juveniles, respectively. During the study, central nervous symptoms and signs of gastrointestinal affection were only demonstrated in adult birds. Our findings indicate a great role of the age at the time of infection in the development of histopathological lesions and clinical signs, and thus provide a better understanding of the pathogenesis, possible virus transmission routes, and the development of carrier birds posing a risk to psittacine collections.

Experimental pathogenesis of aquatic bird bornavirus 1 in Pekin ducks

“…This nding is similar to what observed in Muscovy ducks, 13 and in disagreement with what reported in psittacine birds infected with PaBVs. 23,24 Lack of ABBV-1 immunoreactivity in the kidney is consistent with the low number of positive cloacal swabs (< 0.01% of the total) seen in our cohort. Presence of virus RNA without ABBV-1 N protein expression may indicate tissue-speci c downregulation of virus protein expression.…”

“…Similar wide tissue distribution of the virus has been documented in natural and experimental ABBV-1 infections in waterfowl 7,13 and in psittacine birds experimentally infected with PaBV. 21,22,23 In the nervous tissue, immunoreactivity was not associated with areas of in ammation, and appeared multifocally and randomly distributed. No immunoreactivity was observed in the kidneys, despite high virus RNA concentrations.…”

Experimental pathogenesis of aquatic bird bornavirus 1 in Pekin ducks

“…No immunoreactivity was observed in the kidneys, despite high virus RNA concentrations. This finding is similar to what observed in Muscovy ducks 14 , and in disagreement with what reported in psittacine birds infected with PaBVs 24 , 27 . Lack of ABBV-1 immunoreactivity in the kidney is consistent with the low number of positive cloacal swabs (< 0.01% of the total) seen in our cohort.…”

“…Immunohistochemistry showed presence of ABBV-1 N protein in multiple tissues of IC and IM birds at 21 wpi, and in the single CH duck also at 21 wpi that was positive by RT-qPCR across multiple tissues. Similar wide tissue distribution of the virus has been documented in natural and experimental ABBV-1 infections in waterfowl 8 , 14 and in psittacine birds experimentally infected with PaBV 23 , 24 , 26 . In the nervous tissue, immunoreactivity was not associated with areas of inflammation, and appeared multifocally and randomly distributed.…”

“…The sequence of positive tissues over time indicates both centrifugal (brain to spinal cord, proventriculus, kidneys, and gonads) and centripetal (muscle to spinal cord and brain) virus spread in both the IC and IM groups, respectively, as also seen for ABBV-1 in chickens and Muscovy ducks, and PaBVs in psittacines 14 , 15 , 23 , 24 . This suggests intra-axonal virus trafficking, as proven with BoDV-1 25 , especially in light of the fact that viremia was not detected in our Pekin ducks.…”