Virus strain influenced the interspecies transmission of influenza D virus between calves and pigs

Authors: KAPLAN, BRYAN - Orise Fellow; Falkenberg, Shollie; Dassanayake, Rohana; Neill, John; VELAYUDHAN, BINU - North Carolina Veterinary Diagnostics Laboratory; LI, FENG - South Dakota State University; Baker, Amy

Submitted to: Transboundary and Emerging Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2020
Publication Date: 12/1/2020
Citation: Kaplan, B.S., Falkenberg, S.M., Dassanayake, R.P., Neill, J.D., Velayudhan, B., Li, F., Vincent, A.L. 2020. Virus strain influenced the interspecies transmission of influenza D virus between calves and pigs. Transboundary and Emerging Diseases. https://doi.org/10.1111/tbed.13943.
DOI: https://doi.org/10.1111/tbed.13943

Interpretive Summary: Influenza D virus (IDV) can be repeatably detected in diagnostic samples from cattle, as well as high seropositive rates have been detected in US cattle. While detection of IDV is high in cattle, the first IDV isolate was detected from a clinical sample collected from pigs exhibiting influenza-like illness. Despite the initial detection in porcine, there have been few subsequent reports of IDV in swine populations. The major reservoir for IDV is considered to be domestic cattle, making IDV unique among influenza viruses. To better understand the potential for interspecies transmission of IDV, the current study evaluated transmission between cattle and swine as well as investigated differences in virus detection and transmission that may exist between IDV isolates originating either from cattle or swine. No clinical signs were observed for any of the animals on study, and the species of IDV origin (cattle or swine) had no effect on virus detection in the upper respiratory tract of inoculated calves and pigs, as observed by similar shedding profiles were for each species and virus. However, interspecies transmission was found to be associated with virus origin-species; the bovine isolate only transmitted to cattle and the swine isolate only transmitted to pigs. Together, these data show that cattle and pigs are permissive for IDV replication, but IDV transmission may be species-dependent.

Technical Abstract: Influenza D viruses (IDV) are a recently discovered taxa of Orthomyxoviridae. IDV is the etiologic agent of acute, mild respiratory disease in ungulate species with agricultural importance (cattle, pigs, sheep, goats, camels, etc.). Despite the initial isolate being of porcine origin, serological data suggest cattle to be the primary host of IDV. The study aims were twofold: elucidating species-specific replication kinetics of IDV in bovine and porcine hosts and defining the interspecies potential with two different IDV strains. Three calves and three pigs were intranasally-inoculated with the archetypal strain D/swine/Oklahoma/1334/2017 or a genetically distinct cattle isolate, D/bovine/Texas/72/2017. Two days following infection three naïve pigs and three naïve calves were co-housed with inoculated calves and pigs, respectively. No clinical signs were apparent, and the species of IDV origin had no effect on virus replication kinetics in the upper respiratory tract of inoculated calves and pigs; similar shedding profiles were observed for each species and virus. However, interspecies transmission was found to be associated with virus origin-species; D/bovine/Texas/72/2017 and D/swine/Oklahoma/1334/2017 were directly transmitted only to contact calves or pigs, respectively. Even so, transmission efficiency was higher for calves compared to pigs. Together, these data show that cattle and pigs are permissive for IDV replication, but IDV transmission may be species-dependent. Host-specific mutations may influence transmission efficiencies between agriculturally important mammalian species.