Experimental infection of aquatic bird bornavirus in Muscovy ducks

Abstract

Aquatic bird bornavirus (ABBV-1), an avian bornavirus, has been reported in wild waterfowl from North America and Europe that presented with neurological signs and inflammation of the central and peripheral nervous systems. The potential of ABBV-1to infect and cause lesions in commercial waterfowl species is unknown. The aim of this study was to determine the ability of ABBV-1 to infect and cause disease in day-old Muscovy ducks (n = 174), selected as a representative domestic waterfowl. Ducklings became infected with ABBV-1 through both intracranial and intramuscular, but not oral, infection routes. Upon intramuscular infection, the virus spread centripetally to the central nervous system (brain and spinal cord), while intracranial infection led to virus spread to the spinal cord, kidneys, proventriculus, and gonads (centrifugal spread). Infected birds developed both encephalitis and myelitis by 4 weeks post infection (wpi), which progressively subsided by 8 and 12 wpi. Despite development of microscopic lesions, clinical signs were not observed. Only five birds had choanal and/or cloacal swabs positive for ABBV-1, suggesting a low potential of Muscovy ducks to shed the virus. This is the first study to document the pathogenesis of ABBV-1 in poultry species, and confirms the ability of ABBV-1 to infect commercial waterfowl.

Transcriptome Analysis of Duck and Chicken Brains Infected with Aquatic Bird Bornavirus-1 (ABBV-1)

“…Given the circulation of bornaviruses in multiple avian species [ 14 ], it is possible that ABBV-1 could spill over and infect domestic poultry. Two recent studies from our group support this notion, as we have shown that ABBV-1 can infect and establish persistent infection in the nervous tissues of Muscovy ducks ( Cairina moschata ) and chickens ( Gallus gallus ), upon intracranial and intramuscular inoculation [ 15 , 16 ]. In these studies, the ducks appeared to be markedly susceptible to infection, as suggested by the high levels of virus replication in their nervous tissues and the widespread virus distribution in multiple visceral organs, as opposed to the chickens, in which the infection was mostly limited to the nervous tissue without visceral involvement, with comparatively low levels of virus replication [ 15 , 16 ].…”

“…Two recent studies from our group support this notion, as we have shown that ABBV-1 can infect and establish persistent infection in the nervous tissues of Muscovy ducks ( Cairina moschata ) and chickens ( Gallus gallus ), upon intracranial and intramuscular inoculation [ 15 , 16 ]. In these studies, the ducks appeared to be markedly susceptible to infection, as suggested by the high levels of virus replication in their nervous tissues and the widespread virus distribution in multiple visceral organs, as opposed to the chickens, in which the infection was mostly limited to the nervous tissue without visceral involvement, with comparatively low levels of virus replication [ 15 , 16 ]. This partly agrees with another in vitro study, in which we showed that ABBV-1 can readily infect primary and immortalized duck-embryo fibroblasts, but not chicken-embryo fibroblasts [ 17 ].…”

“…This work is an extension of two previously described experimental infection trials [ 15 , 16 ], from which the brain samples were derived. Detailed experimental design and infection protocols for both ducks and chickens can be found in the referenced studies.…”

“…Tissues for histopathology were fixed in 10% neutral buffered formalin and processed routinely. The severity of inflammation was scored by assessing the extent and magnitude of perivascular lymphocytic cuffs around vessels, and ranged between 0 and 6, as detailed elsewhere [ 15 , 16 ]. The remainder of the brain tissue was stored in RNA preserving solution (20 mM ethylenediaminetetraacetic acid [EDTA], 25 mM sodium citrate, and 70% ( w / v ) ammonium sulfate with a pH of 5.2).…”

“…The remainder of the brain tissue was stored in RNA preserving solution (20 mM ethylenediaminetetraacetic acid [EDTA], 25 mM sodium citrate, and 70% ( w / v ) ammonium sulfate with a pH of 5.2). The magnitude of virus replication was assessed by RT-qPCR for the ABBV-1 N gene by interpolating the cycle threshold value of the samples against a known dilution of the target region (gene block) and reported as viral RNA copies per 150 ng of total tissue RNA [ 15 , 16 ]. The rest of the tissues were used for the RNAseq experiment.…”