Abstract
BackgroundProventricular dilatation disease (PDD) is a fatal disorder of psittacine birds worldwide. The disease is characterized by lymphoplasmacytic infiltration of the central and peripheral nervous systems, leading to gastrointestinal motility and/or central nervous system dysfunction. Recently, we detected a significant association between avian bornavirus (ABV) infection and clinical signs of PDD in psittacines. However, it remains unclear whether ABV infection actually causes PDD. To address this question, we examined the impact of ABV inoculation on the cockatiel (Nymphicus hollandicus).ResultsFive cockatiels were inoculated via multiple routes (intramuscular, intraocular, intranasal, and oral) with a brain homogenate derived from either a PDD(+) avian bornavirus 4 (ABV4) (+) case (n = 3 inoculees) or from a PDD(-) ABV(-) control (n = 2 inoculees). The control birds remained free of clinical or pathological signs of PDD, and tested ABV(-) by RT-PCR and immunohistochemistry (IHC). In contrast, all three cockatiels inoculated with ABV4(+) brain homogenate developed gross and microscopic PDD lesions, and two exhibited overt clinical signs. In numerous tissues, ABV RT-PCR and sequence analysis demonstrated the presence of ABV4 RNA nearly identical to that in the inoculum. ABV was detected in the central nervous system of the three ABV-inoculees by IHC. Pyrosequencing to investigate the viral flora in the ABV4(+) inoculum uncovered 7 unique reads sharing 73–100% nucleotide sequence identity with previously identified ABV sequences and 24 reads sharing 40–89% amino acid sequence identity with viruses in the Retroviridae and Astroviridae families. Of these candidate viral species, only ABV RNA was recovered from tissues of the inoculated birds.ConclusionIn this study, the clinical and pathological manifestations of PDD were induced by inoculation of cockatiels with brain homogenates containing avian bornavirus 4. By using high throughput pyrosequencing an in-depth view of the viral content of the inoculum was achieved, revealing that of 3 candidate virus families detected, only the presence of ABV RNA correlated with the development of PDD. This study provides evidence of a causal association between ABV4 infection and PDD in cockatiels.
Highlights
Proventricular dilatation disease (PDD) is a fatal disorder of psittacine birds worldwide
Clinical observations and post-mortem macroscopic findings Five cockatiels were each inoculated via multiple routes with a brain homogenate derived from either a PDD(+) avian bornavirus (ABV)(+) bird (n = 3) or from a PDD(-) ABV(-) bird (n = 2)
Tissue distribution and localization of ABV detected in inoculees Upon detection of transmission of ABV infection and PDD signs and symptoms in the ABV-inoculees, we investigated the viremia, viral shedding, tissue distribution and subcellular localization of avian bornavirus 4 (ABV4) by RT-PCR for ABV nucleocapsid (ABVN) RNA and immuno-histochemistry for ABVN protein
Summary
Proventricular dilatation disease (PDD) is a fatal disorder of psittacine birds worldwide. The disease is characterized by lymphoplasmacytic infiltration of the central and peripheral nervous systems, leading to gastrointestinal motility and/or central nervous system dysfunction. We detected a significant association between avian bornavirus (ABV) infection and clinical signs of PDD in psittacines. It remains unclear whether ABV infection causes PDD. To address this question, we examined the impact of ABV inoculation on the cockatiel (Nymphicus hollandicus). Proventricular dilatation disease (PDD) is a fatal inflammatory disease of psittacine birds (parrots), characterized by lymphoplasmacytic infiltration of the central and peripheral nervous systems, leading to gastrointestinal (GI) motility malfunction and/or central nervous system disorders. The clinical course of the disease can vary, PDD is generally fatal if left untreated [3]
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