Praveen Akmeemana, University of Guelph

Praveen Akmeemana (1), Alexander Leacy (1), Igor Santos (1), Melanie M. Goens (1), Phuc H. Pham (1), Sarah K. Wootton (1), Leonardo Susta (1). (1) Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada

Suppressing & Conquering

Newcastle disease virus (NDV), an avian orthoavulavirus, is a promising live vaccine vector with a strong safety record, however its biodistribution and environmental shedding profiles remain poorly characterized. This study evaluated both parameters in multiple animal models using a live NDV vector expressing the cleavage site ablated H5 avian influenza hemagglutinin, or a green fluorescent protein (control). Chickens and turkeys (6–9/group) received escalating doses of 105–107 focus-forming units (FFU) per bird; hamsters (8–12/group) received 107 FFU; ferrets (12/group) 108 FFU; and sheep (4/group) 109 FFU. Both oculo-nasal or parenteral routes were employed. Oral and cloacal/rectal swabs were collected within 7 days post-prime (dpp) and post-boost (dpb), and at necropsy (14–21 dpb). NDV RNA was quantified by RT-qPCR, with cycle threshold (Ct) values ≥35 considered negative. Major organs (kidney, spleen, liver, brain, lung, heart) were also tested. No animals developed clinical signs or lesions. In chickens, 35/280 swabs (12.5%) were positive, primarily at 3 and 7 dpp, with none positive at necropsy; the lowest Ct corresponded to ~300 RNA copies/10 µL of swab fluid. In turkeys, 2/249 swabs (0.8%) were positive at 3 and 7 dpp (~200 copies). Hamsters showed 4/160 positives (2.5%) exclusively at 2 dpp, whereas all swabs from ferrets (192) and sheep (96) were negative. No tissues from any species tested positive. Overall, the NDV vector demonstrated a high safety profile, absence of systemic replication, and only transient, low-level shedding near administration, with chickens appearing the most permissive host, albeit to a limited extent.