Experimental infection of alpacas (Vicugna pacos) with influenza C or D viruses results in subclinical upper respiratory tract disease

Influenza D virus (IDV), a new genus within the <i>Orthomyxoviridae</i> family, was initially detected in pigs and cattle. IDV is structurally similar to the influenza C virus (ICV). Influenza A, C and D viruses all have non-human maintenance hosts and likely circulate in several mammalian species. Camelids, as a reservoir for zoonotic viruses, were not extensively studied until the emergence of the Middle East respiratory syndrome coronavirus in 2012. Antibody responses to both ICV and IDV could be detected in dromedary camels from Kenya but not differentiated, owing to cross-reactivity. It was unclear whether these findings reflected a technical issue or suggested a role for camelids in ICV and IDV ecology. In the present study, therefore, alpacas (<i>Vicugna pacos</i>), a camelid species, were experimentally inoculated with ICV (C/Victoria/1/2011) or IDV (D/bovine/France/5920/2014) to assess susceptibility and assess the antibody response. We have demonstrated that alpacas can be experimentally infected with both ICV and IDV with subclinical infection of the upper respiratory tract, suggesting that virus transmission could potentially occur. These findings accord with previous serology results obtained for camelids and indicate a putative role for these species in ICV and IDV ecology.