Pigeons exhibit low susceptibility and poor transmission capacity for H5N1 clade 2.3.4.4b high pathogenicity avian influenza virus.

Abstract

The ongoing panzootic of H5N1 high pathogenicity avian influenza virus (HPAIV) has caused the deaths of over half a billion wild birds and poultry and has led to spillover events in both wild and domestic mammals, alongside sporadic human infections. A key driver of this panzootic is the apparent high viral fitness across diverse avian species, which facilitates an increased interface between wild and domestic species. Columbiformes (pigeons and doves) are commonly found on poultry premises, yet little is known about their potential role in contemporary HPAIV disease ecology. Here, we investigated the epidemiological role of pigeons (Columba livia) by determining their susceptibility using decreasing doses of clade 2.3.4.4b H5N1 HPAIV (genotype AB). We investigated infection outcomes and transmission potential between pigeons and chickens. Following direct inoculation, pigeons did not develop clinical signs, and only those inoculated with the highest dose shed viral RNA (vRNA) or seroconverted to H5N1-AB, revealing a 50% minimum infectious dose (MID) of 10⁵ 50% egg infectious dose. Even in the high-dose group, only low-level shedding and environmental contamination were observed, and low-level viral RNAs were present in the tissues of directly inoculated pigeons, with no distinct pathological lesions. Pigeons did not transmit the virus to pigeons or chickens placed in direct contact. We observed distinct differences in sialic acid receptor distribution in the pigeon respiratory tract compared to chickens and ducks. Together, these findings suggest that pigeons have low susceptibility to clade 2.3.4.4b H5N1 HPAIV and are unlikely to contribute significantly to virus maintenance, transmission to poultry or zoonotic infection.