Wild aquatic birds, a natural reservoir of avian influenza viruses (AIVs), transmit AIVs to poultry farms, causing huge economic losses. Therefore, the prevalence and genetic characteristics of AIVs isolated from wild birds in South Korea from October 2019 to March 2020 were investigated and analyzed. Fresh avian fecal samples (3256) were collected by active monitoring of 11 wild bird habitats. Twenty-eight AIVs were isolated. Seven HA and eight NA subtypes were identified. All AIV hosts were Anseriformes species. The HA cleavage site of 20 representative AIVs was encoded by non-multi-basic amino acid sequences. Phylogenetic analysis of the eight segment genes of the AIVs showed that most genes clustered within the Eurasian lineage. However, the HA gene of H10 viruses and NS gene of four viruses clustered within the American lineage, indicating intercontinental reassortment of AIVs. Representative viruses likely to infect mammals were selected and evaluated for pathogenicity in mice. JB21-58 (H5N3), JB42-93 (H9N2), and JB32-81 (H11N2) were isolated from the lungs, but JB31-69 (H11N9) was not isolated from the lungs until the end of the experiment at 14 dpi. None of infected mice showed clinical sign and histopathological change in the lung. In addition, viral antigens were not detected in lungs of all mice at 14 dpi. These data suggest that LPAIVs derived from wild birds are unlikely to be transmitted to mammals. However, because LPAIVs can reportedly infect mammals, including humans, continuous surveillance and monitoring of AIVs are necessary, despite their low pathogenicity.

Adenovirus has been detected in a wide range of hosts like dogs, foxes, horses, bats, avian animals, and raccoon dogs. Canine adenoviruses with two serotypes host mammals and are members of the mastadenovirus family. Canine adenovirus type 1 (CAdV-1) and canine adenovirus type 2 (CAdV-2) cause infectious canine hepatitis and infectious bronchial disease, respectively. In this study, we investigated the prevalence of CAdV-1 and 2 in wild Nyctereutes procyonoides in Korea in 2017–2020 from 414 tissue samples, including the liver, kidney, lung, and intestine, collected from 105 raccoon dog carcasses. Only CAdV-2 was detected in two raccoon dogs, whereas CAdV-1 was not detected. Tissue samples from raccoon dogs were screened for CAdV-1 and CAdV-2 using conventional PCR. Adenovirus was successfully isolated from PCR positive samples using the Vero cell line, and the full-length gene sequence of the isolated viruses was obtained through 5’ and 3’ rapid amplification of cDNA ends (RACE). The major genes of the isolated CAdV-2/18Ra54 and CAdV-2/18Ra-65 strains showed the closest relationship with that of the CAdV-2 Toronto A26/61 strain isolated from Canada in 1976. There is no large mutation between CAdV-2, which is prevalent worldwide, and CAdV-2, which is prevalent in wild animals in Korea. In addition, it is still spreading and causing infections. The Toronto A26/61 strain, which showed the most similarity to CAdV-2/18Ra-54, was likely transmitted to wild animals through vaccinated companion animals, suggesting that further research is needed on safety measures surrounding animal vaccination. This study provides information on the genetic characteristics and prevalence of canine adenovirus in domestic wild animals and provides a better understanding of canine adenovirus.

The 2009 influenza A H1N1 pandemic (pdm09) originated from the influenza A virus of swine (IAV‐S) through multiple reassortment events with avian and human IAVs. The pdm09 reportedly reintroduced the virus to pigs, contributing to the evolution and diversity of IAV‐S through frequent reassortment and drifts. Surveillance and whole‐genome sequencing of IAV‐S from conventional pig farms in Korea during 2021–2022 revealed that the genetic diversity of H1 and H3 IAV‐S was continuously enriched after human‐to‐swine spillover of pdm09 viruses with long‐term maintenance, persistence, and reassortment of virus lineages. Evidence of additional human‐to‐swine spillover of viruses that are different from the 2009 virus but close to that of the recent H1N1pdm09 human vaccine was identified in this study. The identification of swine‐adapted pdm09 viruses, which have accumulated amino acid mutations with potentially altered antigenicity and a unique potential N‐glycosylation site within the haemagglutinin (HA) gene, suggests the distinctive evolution of spillover pdm09 viruses in swine. The genetic constellation of the recently emerging Eurasian avian‐like swine lineage and the preexisting classical swine lineage H1 viruses in Korea has been expanded through reassortment with cocirculating pdm09 viruses and/or H3N2 IAV‐S harboring the pdm09 M gene (H3N2pM). Collectively, after the major shift of Korean IAV‐S from the classical swine lineage to the pdm09 lineage in 2009, the frequent spillover of pdm09 viruses and the circulation of IAV‐S harboring pdm09 gene segments led to the continuous diversification of IAV‐S through antigenic drift and shift, raising concerns about the potential reintroduction of these viruses to humans.

Astroviruses (AstVs) have been detected in a wide range of animal species, including mammals and birds. Recently, a novel AstV associated with neurological symptoms has been detected in the brains of some mammals. Raccoon dog AstV has been reported recently in China. However, there have been no reports in South Korea. Therefore, the present study aimed to detect and genetically characterize AstVs in the intestine and brain tissues of 133 wild raccoon dogs collected in Korea between 2017 and 2019. Of the seven raccoon dogs, AstVs were detected in six intestinal tissues and four brain tissues. Analysis of the capsid protein amino acid sequences of raccoon dog AstVs detected in Korea revealed a high similarity to canine AstVs, suggesting possible interspecies transmission between raccoon dogs and dogs. Phylogenetic and capsid protein amino acid sequence analysis of raccoon dog AstVs detected in the brain the 17-148B strain belonging to the HMO clade and exhibiting conserved sequences found in neurotropic AstVs (NT-AstVs), indicating their potential as NT-AstVs. However, the pathogenicity and transmission routes of the raccoon dog AstV detected in Korea have not yet been elucidated, so further research and continued surveillance for AstV in wild raccoon dogs are needed.

Eun-Jee Na, Su-Beom Chae, Jun-Soo Park, Yoon-Ji Kim, Young-Sik Kim, Jae-Ku Oem. Korean J. Vet. Serv. 2022;45:285-92. https://doi.org/10.7853/kjvs.2022.45.4.285

Na EJ, et al. J Vet Sci. 2021 Jan;22(1):e12. https://doi.org/10.4142/jvs.2021.22.e12