Pathogenesis of Aquatic Bird Bornavirus in Muscovy Ducks

Abstract

Aquatic bird bornavirus (ABBV), a type of avian bornavirus, has been associated with inflammation of the central and peripheral nervous systems and neurological disease in wild waterfowl in North America and Europe. The potential of ABBV to infect and cause lesions in commercial waterfowl species is unknown. The aim of this study was to determine the ability of ABBV to infect and cause disease in day-old Muscovy ducks (n = 174), selected as a representative domestic waterfowl. Ducklings became infected with ABBV through both intracranial and intramuscular 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, suggesting a moderate potential of Muscovy ducks to shed the virus. This is the first study to document the pathogenesis of ABBV in poultry species, and confirms the ability of ABBV to infect commercial waterfowl.

Pathogenesis of Aquatic Bird Bornavirus 1 in Domestic Chickens

“…All experimental procedures involving animals were approved by the University of Guelph Animal Care and Use Committee (Animal Utilization Protocol 3978), and conducted in accordance with the relevant regulations. The experimental outline is similar to what is reported in detail elsewhere (Iverson et al, 2021). A brief description follows.…”

“…A suspension of cell-free virus was produced from immortalized duck embryo broblasts (American Type Culture Collection CCL-141) that were persistently infected with ABBV-1, as previously described (Iverson et al, 2021). Brie y, con uent 100-150 mm dishes of persistently infected CCL-141 cells were lysed with deionized water (osmotic shock) and one cycle of freeze/thaw in a ultra-cold freezer (-80 °C).…”

“…Cell debris and supernatant were then collected, cleared by centrifugation, and the cell-free virus was concentrated by precipitation with PEG-8000 solution (30 % w/v) and resuspended in phosphate-buffered saline (PBS) with 1 % fetal bovine serum (FBS) to a nal volume ratio of 100:1. The virus stock was titered by the tissue culture infectious dose 50 % method (TCID 50 , limiting dilution) in CCL-141 cells, coupled with immuno uorescence (IFA) to detect infected wells, using a monospeci c antibody (Paci c Immunology) against the ABBV-1 nucleocapsid (N) protein (Leacy et al, 2020;Pham et al, 2020;Iverson et al, 2021).…”

“…The nal titer was calculated by the Spearman-Karber formula and reported as focus forming units (FFU) / mL (Iverson et al, 2021). Inoculum for control birds was prepared in the same way from noninfected cells.…”

“…Recently, our laboratory established an animal model of ABBV-1 infection in day-old Muscovy ducks (Cairina moschata), selected as a representative waterfowl species (Iverson et al, 2021). We have shown that ducklings can be infected with ABBV-1 through both intracranial and intramuscular inoculation routes, with high-titer virus replication in tissues, and both centripetal (from peripheral tissues to the central nervous tissue) and centrifugal (from the central nervous tissue to several peripheral sites) virus spread, including intermittent shedding through the choanal and cloacal secretions.…”