Pathogenesis of aquatic bird bornavirus 1 in turkeys of different age

Aquatic bird bornavirus 1 (ABBV1), an orthobornavirus in the family Bornaviridae, displays a broad host range among avian species, including poultry. The pathogenesis of orthobornaviruses, at least in mammals and psittacines, appears to be mediated by the host immune response against the infected nervous tissue, with younger animals showing a milder disease due to immune tolerance. Here, we tested the ability of ABBV1 to infect domestic turkeys (Meleagris gallopavo), with a focus on evaluating the impact of age at infection. Cohorts of 6-week-old (old) and day-old (young) male turkeys were divided into virus-inoculated and control groups, and kept for up to 12 weeks. Results showed that turkeys of both ages were susceptible to ABBV1 infection by intramuscular administration, following a centripetal and limited centrifugal spread, although infection appeared delayed in old compared to young birds. Notably, only young turkeys developed clinical signs and more frequent inflammation of the central nervous system, indicating that infection at a very early age is unlikely to induce tolerance to ABBV1 infection.