Emergence of human-like H3N2 influenza viruses in pet dogs in Guangxi, China
© Chen et al.; licensee BioMed Central. 2015
Received: 13 July 2014
Accepted: 19 January 2015
Published: 3 February 2015
After the 1968 H3N2 pandemic emerged in humans, H3N2 influenza viruses continuously circulated and evolved in nature. An H3N2 variant was circulating in humans in the 1990s and subsequently introduced into the pig population in the 2000s. This virus gradually became the main subtype of swine influenza virus worldwide. However, there were no reports of infections in dogs with this virus.
In 2013, 35 nasal swabs from pet dogs were positive for Influenza A virus by RT-PCR. Two viruses were isolated and genetically characterized. In the phylogenetic trees of all gene segments, two H3N2 canine isolates clustered with Moscow/10/99 and most H3N2 swine influenza viruses. These results indicated that two H3N2 CIVs possessed high homology with human/swine influenza viruses, which at the same time exhibited some amino acid substitutions in NA, polymerase basic protein 1 (PB1), and nucleoprotein (NP), which probably were related to the interspecies transmission.
These two viruses share the highest homology with swine H3N2, Moscow/99-like viruses, which indicated that these viruses might originate from swine viruses.
KeywordsPet dogs H3N2 subtype Human-like influenza viruses
Influenza A viruses circulate worldwide and are endemic in multiple species from birds to mammals . Historically, dogs have been infected with different subtypes of influenza viruses. After the interspecies transmission of influenza H3N8 viruses from horses to dogs was reported in 2005, avian-origin H5N1, H3N2, H5N2 and H9N2, pdm09 H1N1 human, and novel H3N1 influenza viruses with pdm/09 internal genes were also isolated from dogs [2-8]. Recently, a serological survey proved that dogs could be infected with human influenza viruses, and different subtypes of influenza viruses even coexist in dogs [9-11]. Infection of dogs with human H3N2 viruses has been reported [12-14], however, there was a lack of virological evidence about seasonal human H3N2 influenza viruses in dogs. Here, we present the results of genetic and phylogenetic characterization of H3N2 canine influenza viruses (CIVs) isolated in 2013 in Guangxi, China. Genetic analysis demonstrated that human-like H3N2 swine influenza viruses appeared in pet dogs. It provides further evidence that dogs can be regarded as intermediate hosts and can play an important role in influenza ecology.
Description of two H3N2 canine influenza viruses from Guangxi in 2013
gastroenteritis, diarrhea, Canine Parvovirus Virus (CPV) positive
Cough, sneeze, nasal discharge, low appetite, depression; body temperature:39.5°C
Sequence identity of genes of the two H3N2 CIVs isolated in Guangxi to related sequence in GenBank
Virus with highest identity
Identities a (%)
GenBank accession No.
Influenza virus lineage
Common amino acid changes compared to Moscow/10/99 strain b
T192I, V196A, V226I, K239N(L2)
S44P, V240I, L370S, V398I, I464L
E75D, R189K, G354R(L2), F512L(L1), M718L(L2)
E241D, F600L, T745A
M105I, I119T(L1), R195G(L1), 251I(L1), A251V(L1),D290N, K357R, A493T
M1: S275P; M2: G184R(L1), G199R(L1)
There were no deletions in the neuraminidase (NA) stalk region. However, S44P, V240I and V398I substitutions were found in the NA protein of both CIVs. Besides, substitution R189K in PB1 and A493T in NP genes were present in CIVs differed from swine or human influenza viruses (Table 2). Further experiments are required to explore whether these mutations will help human-like H3N2 viruses adapt to dogs.
A total of 315 canine blood samples were separated by centrifugation at 2000 rpm for 10 min and the supernatants were collected into Eppendorf tubes and stored at −20°C, for testing the antibody titer against H3N2 CIVs by hemagglutination inhibition (HI), as previously described . An HI titer ≧40 was considered positive. All tested samples were negative (data not shown). A previous serological survey showed only a 1.2% seropositive rate of human H3N2 influenza viruses in dogs . Ramirez-Martinez, et al. also reported that the seroprevalence of human influenza in dogs only reached 0.9% . All these results suggest that the number of dogs infected with H3N2 human influenza viruses seems to be limited, which means that human influenza viruses have not spread or established themselves in the canine population yet. However, dogs possess specific receptors for human (α2,6-NeuAcGal) and avian (α2,3-NeuAcGal) viruses [20,21], which implies that dogs can be regarded as intermediate hosts that can become co-infected with different subtypes of influenza viruses. Furthermore, pet dogs share the same environment with humans and are in close contact with their owners, therefore increasing the opportunities for pet dogs to be exposed to human influenza viruses.
Emergence of human-like H3N2 influenza viruses in pet dogs, with or without any clinical signs, raises further concerns about whether the viruses have crept into the dog population, and whether novel reassortant influenza viruses will emerge from infection of pet dogs that pose a potential threat to public health. Continued surveillance for influenza viruses in dogs will become essential.
We thank the anonymous reviewer for critical comments and suggestions. We also thank Professor Ashour Joseph for his valuable comments and guidelines. We thank all the Animal Clinics of Guangxi. The Project was sponsored by the Scientific Research Foundation of Guangxi University (Grant No. XJZ140236) and was founded by National agricultural technology system modernization (Grant No. nycytxgxcxtd-03-15-1).
- Webster RG, Bean WJ, Gorman OT, Chambers TM, Kawaoka Y. Evolution and ecology of influenza A viruses. Microbiol Rev. 1992;56:152–79.PubMed CentralPubMedGoogle Scholar
- Crawford PC, Dubovi EJ, Castleman WL, Stephenson I, Gibbs EP, Chen L, et al. Transmission of equine influenza virus to dogs. Science. 2005;310:482–5.View ArticlePubMedGoogle Scholar
- Lin D, Sun S, Du L, Ma J, Fan L, Pu J, et al. Natural and experimental infection of dogs with pandemic H1N1/2009 influenza virus. J Gen Virol. 2012;93:119–23.View ArticlePubMedGoogle Scholar
- Song D, Lee C, Kang B, Jung K, Oh T, Kim H, et al. Experimental infection of dogs with avian-origin canine influenza A virus (H3N2). Emerg Infect Dis. 2009;15:56–8.View ArticlePubMed CentralPubMedGoogle Scholar
- Song D, Moon HJ, An DJ, Jeoung HY, Kim H, Yeom MJ, et al. A novel reassortant canine H3N1 influenza virus between pandemic H1N1 and canine H3N2 influenza viruses in Korea. J Gen Virol. 2012;93:551–4.View ArticlePubMed CentralPubMedGoogle Scholar
- Song QQ, Zhang FX, Liu JJ, Ling ZS, Zhu YL, Jiang SJ, et al. Dog to dog transmission of a novel influenza virus (H5N2) isolated from a canine. Vet Microbiol. 2013;161:331–3.View ArticlePubMedGoogle Scholar
- Songserm T, Amonsin A, Jam-on R, Sae-Heng N, Pariyothorn N, Payungporn S, et al. Fatal avian influenza A H5N1 in a dog. Emerg Infect Dis. 2006;12:1744–7.View ArticlePubMed CentralPubMedGoogle Scholar
- Sun X, Xu X, Liu Q, Liang D, Li C, He Q, et al. Evidence of avian-like H9N2 influenza A virus among dogs in Guangxi, China. Infect Genet Evol. 2013;20:471–5.View ArticlePubMedGoogle Scholar
- Horimoto T, Gen F, Murakami S, Iwatsuki-Horimoto K, Kato K, Akashi H, et al. Serological evidence of infection of dogs with human influenza viruses in Japan. Vet Rec. 2014;174:96.View ArticlePubMedGoogle Scholar
- Ramirez-Martinez LA, Contreras-Luna M, De la Luz J, Manjarrez ME, Rosete DP, Rivera-Benitez JF, et al. Evidence of transmission and risk factors for influenza A virus in household dogs and their owners. Influenza Other Respir Viruses. 2013;7:1292–6.View ArticlePubMedGoogle Scholar
- Sun Y, Shen Y, Zhang X, Wang Q, Liu L, Han X, et al. A serological survey of canine H3N2, pandemic H1N1/09 and human seasonal H3N2 influenza viruses in dogs in China. Vet Microbiol. 2014;168:193–6.View ArticlePubMedGoogle Scholar
- Chang CP, New AE, Taylor JF, Chiang HS. Influenza virus isolations from dogs during a human epidemic in Taiwan. Int J Zoonoses. 1976;3:61–4.PubMedGoogle Scholar
- Madhavan HN, Agarwal SC. Sero-epidemiology of human and canine influenza in Pondicherry, South India, during 1971–1974. Indian J Med Res. 1976;64:835–40.PubMedGoogle Scholar
- Nikitin A, Cohen D, Todd JD, Lief FS. Epidemiological studies of A-Hong Kong-68 virus infection in dogs. Bull World Health Organ. 1972;47:471–9.PubMed CentralPubMedGoogle Scholar
- Fouchier RA, Bestebroer TM, Herfst S, Van Der Kemp L, Rimmelzwaan GF, Osterhaus AD. Detection of influenza A viruses from different species by PCR amplification of conserved sequences in the matrix gene. J Clin Microbiol. 2000;38:4096–101.PubMed CentralPubMedGoogle Scholar
- Hoffmann E, Stech J, Guan Y, Webster RG, Perez DR. Universal primer set for the full-length amplification of all influenza A viruses. Arch Virol. 2001;146:2275–89.View ArticlePubMedGoogle Scholar
- Yu H, Zhang GH, Hua RH, Zhang Q, Liu TQ, Liao M, et al. Isolation and genetic analysis of human origin H1N1 and H3N2 influenza viruses from pigs in China. Biochem Biophys Res Commun. 2007;356:91–6.View ArticlePubMedGoogle Scholar
- Matrosovich M, Zhou N, Kawaoka Y, Webster R. The surface glycoproteins of H5 influenza viruses isolated from humans, chickens, and wild aquatic birds have distinguishable properties. J Virol. 1999;73:1146–55.PubMed CentralPubMedGoogle Scholar
- Rogers GN, Paulson JC. Receptor determinants of human and animal influenza virus isolates: differences in receptor specificity of the H3 hemagglutinin based on species of origin. Virology. 1983;127:361–73.View ArticlePubMedGoogle Scholar
- Muranaka M, Yamanaka T, Katayama Y, Hidari K, Kanazawa H, Suzuki T, et al. Distribution of influenza virus sialoreceptors on upper and lower respiratory tract in horses and dogs. J Vet Med Sci. 2011;73:125–7.View ArticlePubMedGoogle Scholar
- Ning ZY, Wu XT, Cheng YF, Qi WB, An YF, Wang H, et al. Tissue distribution of sialic acid-linked influenza virus receptors in beagle dogs. J Vet Sci. 2012;13:219–22.View ArticlePubMed CentralPubMedGoogle Scholar
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.