Influenza D virus (FLUDV) is a novel influenza virus that infects cattle and swine. The goal of this study was to investigate the replication and transmission of bovine FLUDV in guinea pigs. Following direct intranasal inoculation of animals, the virus was detected in nasal washes of infected animals during the first 7 days postinfection. High viral titers were obtained from nasal turbinates and lung tissues of directly inoculated animals. Further, bovine FLUDV was able to transmit from the infected guinea pigs to sentinel animals by means of contact and not by aerosol dissemination under the experimental conditions tested in this study. Despite exhibiting no clinical signs, infected guinea pigs developed seroconversion and the viral antigen was detected in lungs of animals by immunohistochemistry. The observation that bovine FLUDV replicated in the respiratory tract of guinea pigs was similar to observations described previously in studies of gnotobiotic calves and pigs experimentally infected with bovine FLUDV but different from those described previously in experimental infections in ferrets and swine with a swine FLUDV, which supported virus replication only in the upper respiratory tract and not in the lower respiratory tract, including lung. Our study established that guinea pigs could be used as an animal model for studying this newly emerging influenza virus.
IMPORTANCE
Influenza D virus (FLUDV) is a novel emerging pathogen with bovine as its primary host. The epidemiology and pathogenicity of the virus are not yet known. FLUDV also spreads to swine, and the presence of FLUDV-specific antibodies in humans couldindicate that there is a potential for zoonosis. Our results showed that bovine FLUDV replicated in the nasal turbinate and lungs of guinea pigs at high titers and was also able to transmit from an infected animal to sentinel animals by contact. The fact that bovine FLUDV replicated productively in both the upper and lower respiratory tracts of guinea pigs, similarly to virus infection in its native host, demonstrates that guinea pigs would be a suitable model host to study the replication and transmission potential of bovine FLUDV.
Influenza viruses are negative-sense, single-stranded RNA viruses classified in the Orthomyxoviridae family. There are three recognized genera of influenza viruses, designated influenza A virus (IAV or FLUAV), influenza B virus (FLUBV), and influenza C virus (FLUCV). FLUAV and FLUBV have 8 negative-sense, single-stranded RNA segments, whereas FLUCV has only 7 segments. FLUAV proteins include 5 structural proteins, HA (hemagglutinin), NA, M1, M2, and NP (ribonucleoprotein); 3 subunits of the RNA polymerase complex, polymerase basic protein 1 (PB1), polymerase basic protein 2 (PB2), and polymerase acidic protein (PA); and 3 nonstructural proteins, NS1, NS2 (nuclear export protein [NEP]), and PB1-F2 (1). Recent studies have suggested that NS2 and (probably) NS1 of FLUAV are structural proteins that can be detected in virions (2). FLUBV has 6 structural proteins, HA...