Serologic evidence of pandemic (H1N1) 2009 infection in dogs, Italy

Circulation of influenza viruses in the dog population in Kazakhstan (2023-2024)

Background

Dogs in close contact with humans can serve as a source of potentially dangerous reassortant influenza viruses (IVs) with zoonotic potential. The dog's body can serve as a vessel for the emergence of new IVs. These new viruses can become a source of infection for other animals and humans. The potential for zoonotic transmission of IVs from dogs to humans poses a public health risk.

Aim

Study of the circulation of IVs in the dog population in Almaty, Kazakhstan.

Methods

Biosamples (oropharyngeal swabs and blood serum) from dogs were collected from veterinary clinics in Almaty in 2023-2024. Samples were screened using RT-PCR, HI assay, and ELISA.

Results

RT-PCR analysis of 355 nasopharyngeal swabs showed the presence of influenza A virus (IAV) in 32 samples (9.01% of the total number of samples analyzed). When subtyping IAV H1N1 RNA was detected in 19 swabs (5.35%). IAV subtype could not be determined in 13 PCR-positive samples (3.66%). The genetic material of IAV H3N2, H5, H7, and H9, as well as coronavirus, bocavirus, and adenovirus has not been identified. In a serological analysis of 180 blood sera using ELISA, antibodies to IAV were detected in 5.56% (n = 10). The results of the HI assay showed the presence of antihemagglutinins to A/H1N1pdm in 6.11% (11 samples), to A/H3N2 in 9.44% (17 samples), and no antibodies to IAV H5, H7, and type B were detected.

Conclusion

There is no information about human infection with any canine influenza virus. However, many cases of infection in dogs with human IAVs H1N1, H1N1pdm09, and H3N2 have been described. When dogs are co-infected with different IAVs, new recombinant IAVs may emerge that can infect humans and other animals. Therefore, ongoing global surveillance of animal populations is necessary to monitor the evolution and circulation of viruses dangerous to public health. This is also important for timely preparation for the emergence of a new zoonotic influenza virus that has pandemic potential for humans.

Antibodies to Influenza A(H5N1) Virus in Hunting Dogs Retrieving Wild Fowl, Washington, USA

We detected antibodies to H5 and N1 subtype influenza A viruses in 4/194 (2%) dogs from Washington, USA, that hunted or engaged in hunt tests and training with wild birds. Historical data provided by dog owners showed seropositive dogs had high levels of exposure to waterfowl.

Influenza A virus antibodies in dogs, hunting dogs, and backyard pigs in Campeche, Mexico

AIMS

This study aimed to identify exposure to human, swine, and avian influenza A virus subtypes in rural companion and hunting dogs, backyard pigs, and feral pigs.

METHODS AND RESULTS

The study took place in a region of southeastern Mexico where the sampled individuals were part of backyard production systems in which different domestic and wild species coexist and interact with humans. We collected blood samples from pigs and dogs at each of the sites. We used a nucleoprotein enzyme-linked immunosorbent assay to determine the exposure of individuals to influenza A virus. Haemagglutination inhibition was performed on the positive samples to determine the subtypes to which they were exposed. For data analysis, a binomial logistic regression model was generated to determine the predictor variables for the seropositivity of the individuals in the study. We identified 11 positive individuals: three backyard pigs, four companion dogs, and four hunting dogs. The pigs tested positive for H1N1 and H1N2. The dogs were positive for H1N1, H1N2, and H3N2. The model showed that dogs in contact with backyard chickens are more likely to be seropositive for influenza A viruses.

CONCLUSIONS

We demonstrated the essential role hunting dogs could play as intermediate hosts and potential mixing vessel hosts when exposed to human and swine-origin viral subtypes. These results are relevant because these dogs interact with domestic hosts and humans in backyard systems, which are risk scenarios in the transmission of influenza A viruses. Therefore, it is of utmost importance to implement epidemiological surveillance of influenza A viruses in backyard animals, particularly in key animals in the transmission of these viruses, such as dogs and pigs.

Development and Validation of a Panel of One-Step Four-Plex qPCR/RT-qPCR Assays for Simultaneous Detection of SARS-CoV-2 and Other Pathogens Associated with Canine Infectious Respiratory Disease Complex

Canine infectious respiratory disease complex (CIRDC) is the primary cause of respiratory disease in the canine population and is caused by a wide array of viruses and bacterial pathogens with coinfections being common. Since its recognition in late 2019, Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has been reported to cause respiratory disease in dogs. Therefore, the rapid detection and differentiation of SARS-CoV-2 from other common viral and bacterial agents is critical from a public health standpoint. Here, we developed and validated a panel of four one-step multiplex qPCR/RT-qPCR assays for the detection and identification of twelve pathogens associated with CIRDC (canine adenovirus-2, canine distemper virus, canine herpesvirus-1, canine influenza A virus, canine parainfluenza virus, canine pneumovirus, canine respiratory coronavirus, SARS-CoV-2, Bordetella bronchiseptica, Streptococcus equi subsp. zooepidemicus, Mycoplasma cynos, and M. canis), as well as the identification of three main CIV subtypes (i.e., H3N2, H3N8, and H1N1). All developed assays demonstrated high specificity and analytical sensitivity. This panel was used to test clinical specimens (n = 76) from CIRDC-suspected dogs. M. canis, M. cynos, and CRCoV were the most frequently identified pathogens (30.3%, 25.0%, and 19.7% of samples, respectively). The newly emerging pathogens CPnV and SARS-CoV-2 were detected in 5.3% of samples and coinfections were identified in 30.3%. This new multiplex qPCR/RT-qPCR panel is the most comprehensive panel developed thus far for identifying CIRDC pathogens, along with SARS-CoV-2.

Live attenuated influenza A virus vaccines with modified NS1 proteins for veterinary use

Influenza A viruses (IAV) spread rapidly and can infect a broad range of avian or mammalian species, having a tremendous impact in human and animal health and the global economy. IAV have evolved to develop efficient mechanisms to counteract innate immune responses, the first host mechanism that restricts IAV infection and replication. One key player in this fight against host-induced innate immune responses is the IAV non-structural 1 (NS1) protein that modulates antiviral responses and virus pathogenicity during infection. In the last decades, the implementation of reverse genetics approaches has allowed to modify the viral genome to design recombinant IAV, providing researchers a powerful platform to develop effective vaccine strategies. Among them, different levels of truncation or deletion of the NS1 protein of multiple IAV strains has resulted in attenuated viruses able to induce robust innate and adaptive immune responses, and high levels of protection against wild-type (WT) forms of IAV in multiple animal species and humans. Moreover, this strategy allows the development of novel assays to distinguish between vaccinated and/or infected animals, also known as Differentiating Infected from Vaccinated Animals (DIVA) strategy. In this review, we briefly discuss the potential of NS1 deficient or truncated IAV as safe, immunogenic and protective live-attenuated influenza vaccines (LAIV) to prevent disease caused by this important animal and human pathogen.

Influenza A viruses circulating in dogs: A review of the scientific literature

Influenza A viruses (IAV) cause persistent epidemics and occasional human pandemics, leading to considerable economic losses. The ecology and epidemiology of IAV are very complex and the emergence of novel zoonotic pathogens is one of the greatest challenges in the healthcare. IAV are characterized by genetic and antigenic variability resulting from a combination of high mutation rates and a segmented genome that provides the ability to rapidly change and adapt to new hosts. In this context, available scientific evidence is of great importance for understanding the epidemiology and evolution of influenza viruses. The present review summarizes original research papers and IAV infections reported in dogs all over the world. Reports of interspecies transmission of equine influenza viruses H3N2 from birds to dogs, as well as double and triple reassortant strains resulting from reassortment of avian, human, and canine strains have amplified the genetic variety of canine influenza viruses. A total of 146 articles were deemed acceptable by PubMed and the Google Scholar database and were therefore included in this review. The largest number of research articles (n = 68) were published in Asia, followed by the Americas (n = 44), Europe (n = 31), Africa (n = 2), and Australia (n = 1). Publications are conventionally divided into three categories. The first category (largest group) included modern articles published from 2011 to the present (n = 93). The second group consisted of publications from 2000 to 2010 (n = 46). Single papers of 1919, 1931, 1963, 1972, 1975, and 1992 were also used, which was necessary to emphasize the history of the study of the ecology and evolution of the IAV circulating among various mammalian species. The largest number of publications occurred in 2010 (n = 18) and 2015 (n = 11), which is associated with IAV outbreaks observed at that time in the dog population in America, Europe, and Asia. In general, these findings raise concerns that dogs may mediate the adaptation of IAVs to zoonotic transmission and therefore serve as alternative hosts for genetic reassortment of these viruses. The global concern and significant threat to public health from the present coronavirus diseases 2019 pandemic confirms the necessity for active surveillance of zoonotic viral diseases with pandemic potential.

Evidence of influenza infection in dogs and cats in central Chile

As companion animals, dogs and cats live in close contact with humans, generating the possibility of interspecies pathogen transmission events. Equine origin H3N8 and avian origin H5N1 influenza virus have been reported in dogs and cats respectively since 2004 with outbreaks associated with different strains recorded for both species in Asia and North America. To date, there have been no reports of influenza viruses from companion animals in South America. To fill this gap in knowledge, we performed active epidemiological surveillance in shelters that received abandoned animals, backyard production systems and veterinary clinics between May 2017 and January 2019 to estimate the burden of influenza infection in cats and dogs in the central region of Chile. Blood samples, oropharyngeal swabs or both were collected for influenza A virus detection by RT-qPCR, NP-ELISA, and hemagglutination inhibition assay. Logistic regression models were performed to assess the association between NP-ELISA-positivity and variables including sex and animal origin. The percentage of ELISA-positive samples was 43.5 % (95 % CI: 37.0-50.1) and 23.3 % (95 % CI: 10.6-42.7) for dogs and cats, respectively. No association was found between NP-ELISA results and sex or animal origin for either dogs or cats. Two ELISA positive samples showed hemagglutination inhibition titers against pandemic H1N1 influenza. One dog sample tested positive by RT-qPCR, indicating an overall RT-qPCR positivity in dogs of 1.1 % (95 % CI: 0.05-6.7). None of the tested cat samples were positive by this assay.

Molecular Characteristics, Antigenicity, Pathogenicity, and Zoonotic Potential of a H3N2 Canine Influenza Virus Currently Circulating in South China

Canine influenza viruses (CIVs) could be a source of influenza viruses which infect humans because canine are important companion pets. To assess the potential risk of H3N2 CIVs currently circulating in southern China to public health, biological characteristics of A/canine/Guangdong/DY1/2019 (CADY1/2019) were detected. CADY1/2019 bound to both avian-type and human-type receptors. CADY1/2019 had a similar pH value for HA protein fusion to human viruses, but its antigenicity was obviously different from those of current human H3N2 influenza viruses (IVs) or the vaccine strains recommended in the North hemisphere. CADY1/2019 effectively replicated in the respiratory tract and was transmitted by physical contact among guinea pigs. Compared to human H3N2 IV, CADY1/2019 exhibited higher replication in MDCK, A549, 3D4/21, ST, and PK15 cells. Sequence analysis indicated that CADY1/2019 is an avian-origin virus, and belongs to the novel clade and has acquired many adaptation mutations to infect other mammals, including human. Taken together, currently circulating H3N2 CIVs have a zoonotic potential, and there is a need for strengthening surveillance and monitoring of their pathogenicity.

A cluster epidemic of influenza A(H1N1)pdm09 virus infection in four captive cheetahs (Acinonyx jubatus)

In January 2019, four cheetahs (Acinonyx jubatus) kept at a Japanese zoo intermittently showed respiratory signs following the incidence of seasonal influenza in animal caregivers. Respiratory materials (saliva, sputum and food tray swabs) were non-invasively collected from the four cheetahs. Although we were unable to isolate the virus, the NP gene of influenza A virus was detected in three of the cheetahs but not in the fourth cheetah that had nearly recovered. From a food tray swab which tested weakly positive by a commercial influenza detection kit, we were able to obtain the whole-genome sequence of the influenza A virus. Analysis of the genome, A/cheetah/Kanagawa/2/2019(H1N1), revealed that the virus was closely related to influenza A(H1N1)pdm09 viruses isolated from humans in Japan in the 2018-2019 winter. Production of haemagglutinin inhibition (HI) antibodies (64-128 HI) against an A(H1N1)pdm09 virus in plasma samples confirmed infection of all four cheetahs. The animals continued to produce antibodies for at least 314 days after disease onset. These findings strongly suggest that reverse zoonotic transmission of A(H1N1)pdm09 virus occurred from human to cheetah and subsequently from cheetah to cheetah in the zoo. We also show that specimens can be safely and non-invasively collected from non-domesticated animals and used to investigate respiratory infectious diseases.

Canine and Feline Influenza

Influenza virus infections of carnivores-primarily in dogs and in large and small cats-have been repeatedly observed to be caused by a number of direct spillovers of avian viruses or in infections by human or swine viruses. In addition, there have also been prolonged epizootics of an H3N8 equine influenza virus in dogs starting around 1999, of an H3N2 avian influenza virus in domestic dog populations in Asia and in the United States that started around 2004, and an outbreak of an avian H7N2 influenza virus among cats in an animal shelter in the United States in 2016. The impact of influenza viruses in domesticated companion animals and their zoonotic or panzootic potential poses significant questions for veterinary and human health.

Generation and properties of one strain of H3N2 influenza virus with enhanced replication

H3N2 canine influenza virus (CIV) has been circulating in many countries since 2008. The epidemic spread of CIV could be a concern for public health because of the close contact between humans and companion animals. In this study, we used Madin-Darby canine kidney (MDCK) cells as a coinfection model of H3N2 CIV and the pandemic (2009) H1N1 influenza virus to investigate the possibility of genetic mutation or recombination. One of the resultant progeny viruses, designated as CP15, was identified with a significantly increased replication ability. For this viral strain all segments exhibit a homology close to 100 % with its parental strain A/Canine/Jiangsu/06/2010 (JS/10), except for two site mutations K156E and R201 K which occur in the receptor-binding sites of hemagglutinin (HA) and antigen binding sites of neuraminidase (NA), respectively. Virus growth in MDCK cells showed that CP15 had a higher virus titer (more than 10 times) than JS/10. Consistent with this, CP15 exhibited extensive tissue tropism and higher viral RNA loads in the spleen, kidney and lung of mice challenged with this virus compared to JS/10. However, body weight loss and lung injure score due to CP15 infection were greatly reduced. Importantly, anti-CP15 serum antibodies could confer a high neutralization activity against JS/10. These findings indicated that the CP15 strain of high replication ability represents a promising candidate to develop an efficient CIV vaccine.

Reverse Zoonosis of COVID-19: Lessons From the 2009 Influenza Pandemic

Over the past decade, pandemics caused by pandemic H1N1 (pH1N1) influenza virus in 2009 and severe acute respiratory syndrome virus type 2 (SARS-CoV-2) in 2019 have emerged. Both are high-impact respiratory pathogens originating from animals. Their wide distribution in the human population subsequently results in an increased risk of human-to-animal transmission: reverse zoonosis. Although there have only been rare reports of reverse zoonosis events associated with the ongoing coronavirus disease 2019 (COVID-19) pandemic from SARS-CoV-2 so far, comparison with the pH1N1 influenza pandemic can provide a better understanding of the possible consequences of such events for public and animal health. The results of our review suggest that similar factors contribute to successful crossing of the host species barriers in both pandemics. Specific risk factors include sufficient interaction between infected humans and recipient animals, suitability of the animal host factors for productive virus infection, and suitability of the animal host population for viral persistence. Of particular concern is virus spread to susceptible animal species, in which group housing and contact network structure could potentially result in an alternative virus reservoir, from which reintroduction into humans can take place. Virus exposure in high-density populations could allow sustained transmission in susceptible animal species. Identification of the risk factors and serological surveillance in SARS-CoV-2-susceptible animal species that are group-housed should help reduce the threat from reverse zoonosis of COVID-19.

Serological Screening of Influenza A Virus Antibodies in Cats and Dogs Indicates Frequent Infection with Different Subtypes

Influenza A viruses (IAVs) infect humans and a variety of other animal species. Infections with some subtypes of IAV were also reported in domestic cats and dogs. In addition to animal health implications, close contact between companion animals and humans also poses a potential risk of zoonotic IAV infections. In this study, serum samples from different cat and dog cohorts were analyzed for IAV antibodies against seven IAV subtypes, using three distinctive IAV-specific assays differing in IAV subtype-specific discriminatory power and sensitivity. Enzyme-linked immunosorbent assays against the complete hemagglutinin (HA) ectodomain or the HA1 domain were used, as well as a novel nanoparticle-based, virus-free hemagglutination inhibition assay. Using these three assays, we found cat and dog sera from different cohorts to be positive for antibodies against one or more IAV subtypes and/or strains. Cat and dog serum samples collected after the 2009 pandemic H1N1 outbreak exhibit much higher seropositivity against H1 compared to samples from before 2009. Cat sera, furthermore, displayed higher reactivity for avian IAVs than dog sera. Our findings show the added value of using complementary serological assays, which are based on reactivity with different numbers of HA epitopes, to study IAV antibody responses and for improved serosurveillance of IAV infections. We conclude that infection of cats and dogs with both human and avian IAVs of different subtypes is prevalent. These observations highlight the role of cats and dogs in IAV ecology and indicate the potential of these companion animals to give rise to novel (reassorted) viruses with increased zoonotic potential.

Serosurvey of pandemic H1N1 influenza A virus in dogs in Andalusia (southern Spain)

In April 2009, a new influenza A virus (IAV) subtype (A(H1N1)pdm09) spread worldwide and triggered the first human influenza pandemic of the 21st century. Since then, exposure to the pandemic H1N1 IAV has been confirmed in different animal species. Serological evidence and clinical infection with A(H1N1)pdm09 have been reported in canines, but the information available about the role of dogs in the epidemiology of this IAV subtype is still very limited in Europe. A cross-sectional study was carried out to determine the seroprevalence of A(H1N1)pdm09 in dogs in southern Spain, a region with endemic seasonal circulation in human. Sera from 750 companion dogs were collected during the period 2013-2016. Antibodies against pandemic H1N1 IAV were analysed using the haemagglutination inhibition test. Positive samples were also tested by single radial haemolysis assay. Seropositivity was only confirmed by both methods in one (0.13%; 95% CI: 0.00-0.38) adult animal sampled in 2013. To the best of the authors' knowledge, this is the first report of A(H1N1)pdm09 exposure in dogs in Spain. The low seroprevalence obtained indicates a limited exposure history to A(H1N1)pdm09 IAV in dogs in this country and suggests a low risk of transmission of this zoonotic IAV subtype between humans and dogs.

Emergence and Containment of Canine Influenza Virus A(H3N2), Ontario, Canada, 2017-2018

Canine influenza virus (CIV) A(H3N2) was identified in 104 dogs in Ontario, Canada, during December 28, 2017–October 30, 2018, in distinct epidemiologic clusters. High morbidity rates occurred within groups of dogs, and kennels and a veterinary clinic were identified as foci of infection. Death attributable to CIV infection occurred in 2 (2%) of 104 diagnosed cases. A combination of testing of suspected cases, contact tracing and testing, and 28-day isolation of infected dogs was used, and CIV transmission was contained in each outbreak. Dogs recently imported from Asia were implicated as the source of infection. CIV H3N2 spread rapidly within groups in this immunologically naive population; however, containment measures were apparently effective, demonstrating the potential value of prompt diagnosis and implementation of CIV control measures.

Serologic investigation of influenza A virus infection in dogs in Poland

The 2 predominant circulating subtypes of influenza A virus in the dog population, equine-origin H3N8 and avian-origin H3N2, constitute a potential zoonotic risk. We determined the prevalence of influenza A antibodies in 496 dogs in Poland and found 2.21% of sera positive by commercial ELISA. Hemagglutination inhibition (HI) assays indicated 7.25% of sera positive using equine H3N8, swine H3N2, and pandemic H1N1 antigens, with the most frequently detected immune response being to H3N2. Considering interspecies transfer, reassortment ability, and close contact between dogs and humans, infections of dogs with influenza A virus should be monitored.

Influenza A Virus Infection in Cats and Dogs: A Literature Review in the Light of the "One Health" Concept

Influenza A viruses are amongst the most challenging viruses that threaten both human and animal health. Constantly evolving and crossing species barrier, the emergence of novel zoonotic pathogens is one of the greatest challenges to global health security. During the last decade, considerable attention has been paid to influenza virus infections in dogs, as two canine H3N8 and H3N2 subtypes caused several outbreaks through the United States and Southern Asia, becoming endemic. Cats, even though less documented in the literature, still appear to be susceptible to many avian influenza infections. While influenza epidemics pose a threat to canine and feline health, the risks to humans are largely unknown. Here, we review most recent knowledge of the epidemiology of influenza A viruses in dogs and cats, existing evidences for the abilities of these species to host, sustain intraspecific transmission, and generate novel flu A lineages through genomic reassortment. Such enhanced understanding suggests a need to reinforce surveillance of the role played by companion animals-human interface, in light of the “One Health” concept and the potential emergence of novel zoonotic viruses.

Aetiology of Canine Infectious Respiratory Disease Complex and Prevalence of its Pathogens in Europe

The canine infectious respiratory disease complex (CIRDC) is an endemic worldwide syndrome involving multiple viral and bacterial pathogens. Traditionally, Bordetella bronchiseptica (Bb), canine adenovirus type 2 (CAV-2), canine distemper virus (CDV), canine herpesvirus (CHV) and canine parainfluenza virus (CPiV) were considered the major causative agents. Lately, new pathogens have been implicated in the development of CIRDC, namely canine influenza virus (CIV), canine respiratory coronavirus (CRCoV), canine pneumovirus (CnPnV), Mycoplasma cynos and Streptococcus equi subspecies zooepidemicus. To better understand the role of the different pathogens in the development of CIRDC and their epidemiological relevance in Europe, prevalence data were collected from peer-reviewed publications and summarized. Evidence of exposure to Bb is frequently found in healthy and diseased dogs and client-owned dogs are as likely to be infected as kennelled dogs. Co-infections with viral pathogens are common. The findings confirm that Bb is an important cause of CIRDC in Europe. CAV-2 and CDV recovery rates from healthy and diseased dogs are low and the most likely explanation for this is control through vaccination. Seroconversion to CHV can be demonstrated following CIRDC outbreaks and CHV has been detected in the lower respiratory tract of diseased dogs. There is some evidence that CHV is not a primary cause of CIRDC, but opportunistically re-activates at the time of infection and exacerbates the disease. The currently available data suggest that CIV is, at present, neither a prevalent nor a significant pathogen in Europe. CPiV remains an important pathogen in CIRDC and facilitates co-infection with other viral and bacterial pathogens. CnPnV and CRCoV are important new elements in the aetiology of CIRDC and spread particularly well in multi-dog establishments. M. cynos is common in Europe and is more likely to occur in younger and kennelled dogs. This organism is frequently found together with other CIRDC pathogens and is significantly associated with more severe respiratory signs. S. zooepidemicus infection is not common and appears to be a particular problem in kennels. Protective immunity against respiratory diseases is rarely complete, and generally only a reduction in clinical signs and excretion of pathogen can be achieved through vaccination. However, even vaccines that only reduce and do not prevent infection carry epidemiological advantages. They reduce spread, increase herd immunity and decrease usage of antimicrobials. Recommending vaccination of dogs against pathogens of CIRDC will directly provide epidemiological advantages to the population and the individual dog.

Genetic and serologic surveillance of canine (CIV) and equine (EIV) influenza virus in Nuevo León State, México

BACKGROUND

Despite the uncontrolled distribution of the Influenza A virus through wild birds, the detection of canine influenza virus and equine influenza virus in Mexico was absent until now. Recently, outbreaks of equine and canine influenza have been reported around the world; the virus spreads quickly among animals and there is potential for zoonotic transmission.

METHODS

Amplification of the Influenza A virus matrix gene from necropsies, nasal and conjunctival swabs from trash service horses and pets/stray dogs was performed through RT-PCR. The seroprevalence was carried out through Sandwich enzyme-linked immunosorbent assay system using the M1 recombinant protein and polyclonal antibodies anti-M1.

RESULTS

The matrix gene was amplified from 13 (19.11%) nasal swabs, two (2.94%) conjunctival swabs and five (7.35%) lung necropsies, giving a total of 20 (29.41%) positive samples in a pet dog population. A total of six (75%) positive samples of equine nasal swab were amplified. Sequence analysis showed 96-99% identity with sequences of Influenza A virus matrix gene present in H1N1, H1N2 and H3N2 subtypes. The phylogenetic analysis of the sequences revealed higher identity with matrix gene sequences detected from zoonotic isolates of subtype H1N1/2009. The detection of anti-M1 antibodies in stray dogs showed a prevalence of 123 (100%) of the sampled population, whereas in horses, 114 (92.68%) positivity was obtained.

CONCLUSION

The results unveil the prevalence of Influenza A virus in the population of horses and dogs in the state of Nuevo Leon, which could indicate a possible outbreak of equine and Canine Influenza in Mexico. We suggest that the prevalence of Influenza virus in companion animals be monitored to investigate its epizootic and zoonotic potential, in addition to encouraging the regulation of vaccination in these animal species in order to improve their quality of life.

Adaptation of H3N2 canine influenza virus to feline cell culture

H3N2 canine influenza viruses are prevalent in Asian and North American countries. During circulation of the viruses in dogs, these viruses are occasionally transmitted to cats. If this canine virus causes an epidemic in cats too, sporadic infections may occur in humans because of the close contact between these companion animals and humans, possibly triggering an emergence of mutant viruses with a pandemic potential. In this study, we aimed to gain an insight into the mutations responsible for inter-species transmission of H3N2 virus from dogs to cats. We found that feline CRFK cell-adapted viruses acquired several mutations in multiple genome segments. Among them, HA1-K299R, HA2-T107I, NA-L35R, and M2-W41C mutations individually increased virus growth in CRFK cells. With a combination of these mutations, virus growth further increased not only in CRFK cells but also in other feline fcwf-4 cells. Both HA1-K299R and HA2-T107I mutations increased thermal resistance of the viruses. In addition, HA2-T107I increased the pH requirement for membrane fusion. These findings suggest that the mutations, especially the two HA mutations, identified in this study, might be responsible for adaptation of H3N2 canine influenza viruses in cats.

Influenza A in Bovine Species: A Narrative Literature Review

It is quite intriguing that bovines were largely unaffected by influenza A, even though most of the domesticated and wild animals/birds at the human-animal interface succumbed to infection over the past few decades. Influenza A occurs on a very infrequent basis in bovine species and hence bovines were not considered to be susceptible hosts for influenza until the emergence of influenza D. This review describes a multifaceted chronological review of literature on influenza in cattle which comprises mainly of the natural infections/outbreaks, experimental studies, and pathological and seroepidemiological aspects of influenza A that have occurred in the past. The review also sheds light on the bovine models used in vitro and in vivo for influenza-related studies over recent years. Despite a few natural cases in the mid-twentieth century and seroprevalence of human, swine, and avian influenza viruses in bovines, the evolution and host adaptation of influenza A virus (IAV) in this species suffered a serious hindrance until the novel influenza D virus (IDV) emerged recently in cattle across the world. Supposedly, certain bovine host factors, particularly some serum components and secretory proteins, were reported to have anti-influenza properties, which could be an attributing factor for the resilient nature of bovines to IAV. Further studies are needed to identify the host-specific factors contributing to the differential pathogenetic mechanisms and disease progression of IAV in bovines compared to other susceptible mammalian hosts.

Seroprevalence of dogs in Hong Kong to human and canine influenza viruses

As a unique mammalian host for influenza A viruses, dogs support the transmission of canine influenza viruses (CIVs) of H3N8 and H3N2 subtypes and are susceptible to infection by avian and human influenza viruses. A cross-sectional serological study was performed to assess the exposure history of dogs in Hong Kong to CIV and human influenza viruses. Among 555 companion dogs sampled in 2015-2017, 1.3 per cent and 9.5 per cent showed hemagglutination inhibition (HI) antibody titre to CIV of H3N8 or H3N2 subtypes and to A(H1N1)pdm09 human influenza viruses, respectively. Among 182 shelter dogs sampled in 2017-2018, none showed HI titre to CIV and 1.1 per cent reacted to H3N2 human influenza virus. There was a poor correlation between ELISA and HI test results. The higher seropositive rates to human influenza viruses suggests that the contact dynamics of dogs under urban settings may affect the exposure risk to human influenza viruses and CIVs.

Comparative Analysis of Whole-Transcriptome RNA Expression in MDCK Cells Infected With the H3N2 and H5N1 Canine Influenza Viruses

This study aimed to detect changes in the complete transcriptome of MDCK cells after infection with the H5N1 and H3N2 canine influenza viruses using high-throughput sequencing, search for differentially expressed RNAs in the transcriptome of MDCK cells infected with H5N1 and H3N2 using comparative analysis, and explain the differences in the pathogenicity of H5N1 and H3N2 at the transcriptome level. Based on the results of our comparative analysis, significantly different levels of expression were found for 2,464 mRNAs, 16 miRNAs, 181 lncRNAs, and 262 circRNAs in the H3N2 infection group and 448 mRNAs, 12 miRNAs, 77 lncRNAs, and 189 circRNAs in the H5N1 infection group. Potential functions were predicted by performing Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of the target genes of miRNAs, lncRNAs and circRNAs, and the ncRNA-mRNA regulatory network was constructed based on differentially expressed RNAs. A greater number of pathways regulating immune metabolism were altered in the H3N2 infection group than in the H5N1 infection group, which may be one reason why the H3N2 virus is less pathogenic than is the H5N1 virus. This study provides detailed data on the production of ncRNAs during infection of MDCK cells by the canine influenza viruses H3N2 and H5N1, analyzed differences in the total transcriptomes between H3N2- and H5N1-infected MDCK cells, and explained these differences with regard to the pathogenicity of H3N2 and H5N1 at the transcriptional level.

Evidence of pandemic H1N1 influenza exposure in dogs and cats, Thailand: A serological survey

Influenza A virus causes respiratory disease in both humans and animals. In this study, a survey of influenza A antibodies in domestic dogs and cats was conducted in 47 animal shelters in 19 provinces of Thailand from September 2011 to September 2014. One thousand and eleven serum samples were collected from 932 dogs and 79 cats. Serum samples were tested for influenza A antibodies using a multi-species competitive NP-ELISA and haemagglutination inhibition (HI) assay. The NP-ELISA results showed that 0.97% (9/932) of dogs were positive, but all cat samples were negative. The HI test against pandemic H1N1, human H3N2 and canine H3N2 showed that 0.64% (6/932) and 1.20% (1/79) of dogs and cats were positive, respectively. It is noted that all six serum samples (5 dogs and 1 cat) had antibodies against pandemic H1N1. In summary, a serological survey revealed the evidence of pandemic H1N1 influenza exposure in both dogs and cats in the shelters in Thailand.

Comparative pathogenesis of H3N2 canine influenza virus in beagle dogs challenged by intranasal and intratracheal inoculation

As important companion animals, dogs may serve as intermediate hosts for transmitting influenza virus to humans. However, knowledge regarding H3N2 canine influenza virus (CIV) pathogenicity is not comprehensive, which directly affects the animal models of pathogenicity in H3N2 CIV vaccine research. Here, to assess H3N2 CIV pathogenicity, we utilized 30 ten-week-old purpose-bred beagles intratracheally or intranasally inoculated with 10⁶ 50% egg-infectious dose. Intratracheal inoculation was more virulent to dogs than intranasal inoculation as shown by lung pathology score, histopathological changes, clinical symptoms, and body temperature. More intense virus replication was observed in the upper and lower respiratory tracts by intratracheal than intranasal inoculation according to nasal swabs, various organ virus titers, and antigen expression. These results may enhance the H3N2 CIV infection model, providing a more complete experimental basis for studying intrinsic H3N2 CIV pathogenic mechanism, and also serving a reference role for CIV prevention and treatment.

Seroprevalence of three influenza A viruses (H1N1, H3N2, and H3N8) in pet dogs presented to a veterinary hospital in Ohio

The prevalence of canine H3N8 influenza and human H1N1 and H3N2 influenza in dogs in Ohio was estimated by conducting serologic tests on 1,082 canine serum samples. In addition, risk factors, such as health status and age were examined. The prevalences of human H1N1, H3N2, and canine H3N8 influenzas were 4.0%, 2.4%, and 2.3%, respectively. Two samples were seropositive for two subtypes (H1N1 and H3N2; H1N1 and canine influenza virus [CIV] H3N8). Compared to healthy dogs, dogs with respiratory signs were 5.795 times more likely to be seropositive against H1N1 virus (p = 0.042). The prevalence of human flu infection increased with dog age and varied by serum collection month. The commercial enzyme-linked immunosorbent assay used in this study did not detect nucleoprotein-specific antibodies from many hemagglutination inhibition positive sera, which indicates a need for the development and validation of rapid tests for influenza screening in canine populations. In summary, we observed low exposure of dogs to CIV and human influenza viruses in Ohio but identified potential risk factors for consideration in future investigations. Our findings support the need for establishment of reliable diagnostic standards for serologic detection of influenza infection in canine species.

European surveillance of emerging pathogens associated with canine infectious respiratory disease

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The largest study of its kind in the field to date, including high-risk kennelled dogs, and for the first time, pet dogs and dogs from other cohorts.

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A clearly identifiable link between disease and the emerging pathogens: canine respiratory coronavirus and canine pneumovirus.

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Provides, substantial evidence of CIRD and the circulation of the novel pathogens studied in pet dogs, and dogs from other cohorts.

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Demonstrates the role and limitations of current vaccine strategies in managing CIRD outbreaks, and the need for including emerging pathogens.

Canine infectious respiratory disease (CIRD) is a major cause of morbidity in dogs worldwide, and is associated with a number of new and emerging pathogens. In a large multi-centre European study the prevalences of four key emerging CIRD pathogens; canine respiratory coronavirus (CRCoV), canine pneumovirus (CnPnV), influenza A, and Mycoplasma cynos (M. cynos); were estimated, and risk factors for exposure, infection and clinical disease were investigated.

CIRD affected 66% (381/572) of the dogs studied, including both pet and kennelled dogs. Disease occurrence and severity were significantly reduced in dogs vaccinated against classic CIRD agents, canine distemper virus (CDV), canine adenovirus 2 (CAV-2) and canine parainfluenza virus (CPIV), but substantial proportions (65.7%; 201/306) of vaccinated dogs remained affected.

CRCoV and CnPnV were highly prevalent across the different dog populations, with overall seropositivity and detection rates of 47% and 7.7% for CRCoV, and 41.7% and 23.4% for CnPnV, respectively, and their presence was associated with increased occurrence and severity of clinical disease. Antibodies to CRCoV had a protective effect against CRCoV infection and more severe clinical signs of CIRD but antibodies to CnPnV did not.

Involvement of M. cynos and influenza A in CIRD was less apparent. Despite 45% of dogs being seropositive for M. cynos, only 0.9% were PCR positive for M. cynos. Only 2.7% of dogs were seropositive for Influenza A, and none were positive by PCR.

The K186E Amino Acid Substitution in the Canine Influenza Virus H3N8 NS1 Protein Restores Its Ability To Inhibit Host Gene Expression

Canine influenza viruses (CIVs) are the causative agents of canine influenza, a contagious respiratory disease in dogs, and include the equine-origin H3N8 and the avian-origin H3N2 viruses. Influenza A virus (IAV) nonstructural protein 1 (NS1) is a virulence factor essential for counteracting the innate immune response. Here, we evaluated the ability of H3N8 CIV NS1 to inhibit host innate immune responses. We found that H3N8 CIV NS1 was able to efficiently counteract interferon (IFN) responses but was unable to block general gene expression in human or canine cells. Such ability was restored by a single amino acid substitution in position 186 (K186E) that resulted in NS1 binding to the 30-kDa subunit of the cleavage and polyadenylation specificity factor (CPSF30), a cellular protein involved in pre-mRNA processing. We also examined the frequency distribution of K186 and E186 among H3N8 CIVs and equine influenza viruses (EIVs), the ancestors of H3N8 CIV, and experimentally determined the impact of amino acid 186 in the ability of different CIV and EIV NS1s to inhibit general gene expression. In all cases, the presence of E186 was responsible for the control of host gene expression. In contrast, the NS1 protein of H3N2 CIV harbors E186 and blocks general gene expression in canine cells. Altogether, our results confirm previous studies on the strain-dependent ability of NS1 to block general gene expression. Moreover, the observed polymorphism on amino acid 186 between H3N8 and H3N2 CIVs might be the result of adaptive changes acquired during long-term circulation of avian-origin IAVs in mammals.IMPORTANCE Canine influenza is a respiratory disease of dogs caused by two CIV subtypes, the H3N8 and H3N2 viruses, of equine and avian origins, respectively. Influenza NS1 is the main viral factor responsible for the control of host innate immune responses, and changes in NS1 can play an important role in host adaptation. Here we assessed the ability of H3N8 CIV NS1 to inhibit host innate immune responses and gene expression. The H3N8 CIV NS1 did not block host gene expression, but this activity was restored by a single amino acid substitution (K186E), which was responsible for NS1 binding to the host factor CPSF30. In contrast, the H3N2 CIV NS1, which contains E186, blocks general gene expression. Our results suggest that the ability to block host gene expression is not required for influenza virus replication in mammals but might be important in the long-term adaptation of avian-origin influenza viruses to mammals.

Zoonotic Risk, Pathogenesis, and Transmission of Avian-Origin H3N2 Canine Influenza Virus

Two subtypes of influenza A virus (IAV), avian-origin canine influenza virus (CIV) H3N2 (CIV-H3N2) and equine-origin CIV H3N8 (CIV-H3N8), are enzootic in the canine population. Dogs have been demonstrated to seroconvert in response to diverse IAVs, and naturally occurring reassortants of CIV-H3N2 and the 2009 H1N1 pandemic virus (pdmH1N1) have been isolated. We conducted a thorough phenotypic evaluation of CIV-H3N2 in order to assess its threat to human health. Using ferret-generated antiserum, we determined that CIV-H3N2 is antigenically distinct from contemporary human H3N2 IAVs, suggesting that there may be minimal herd immunity in humans. We assessed the public health risk of CIV-H3N2 × pandemic H1N1 (pdmH1N1) reassortants by characterizing their in vitro genetic compatibility and in vivo pathogenicity and transmissibility. Using a luciferase minigenome assay, we quantified the polymerase activity of all possible 16 ribonucleoprotein (RNP) complexes (PB2, PB1, PA, NP) between CIV-H3N2 and pdmH1N1, identifying some combinations that were more active than either parental virus complex. Using reverse genetics and fixing the CIV-H3N2 hemagglutinin (HA), we found that 51 of the 127 possible reassortant viruses were viable and able to be rescued. Nineteen of these reassortant viruses had high-growth phenotypes in vitro, and 13 of these replicated in mouse lungs. A single reassortant with the NP and HA gene segments from CIV-H3N2 was selected for characterization in ferrets. The reassortant was efficiently transmitted by contact but not by the airborne route and was pathogenic in ferrets. Our results suggest that CIV-H3N2 reassortants may pose a moderate risk to public health and that the canine host should be monitored for emerging IAVs.IMPORTANCE IAV pandemics are caused by the introduction of novel viruses that are capable of efficient and sustained transmission into a human population with limited herd immunity. Dogs are a a potential mixing vessel for avian and mammalian IAVs and represent a human health concern due to their susceptibility to infection, large global population, and close physical contact with humans. Our results suggest that humans are likely to have limited preexisting immunity to CIV-H3N2 and that CIV-H3N2 × pdmH1N1 reassortants have moderate genetic compatibility and are transmissible by direct contact in ferrets. Our study contributes to the increasing evidence that surveillance of the canine population for IAVs is an important component of pandemic preparedness.

A bivalent live-attenuated influenza vaccine for the control and prevention of H3N8 and H3N2 canine influenza viruses

Canine influenza viruses (CIVs) cause a contagious respiratory disease in dogs. CIV subtypes include H3N8, which originated from the transfer of H3N8 equine influenza virus (EIV) to dogs; and the H3N2, which is an avian-origin virus adapted to infect dogs. Only inactivated influenza vaccines (IIVs) are currently available against the different CIV subtypes. However, the efficacy of these CIV IIVs is not optimal and improved vaccines are necessary for the efficient prevention of disease caused by CIVs in dogs. Since live-attenuated influenza vaccines (LAIVs) induce better immunogenicity and protection efficacy than IIVs, we have combined our previously described H3N8 and H3N2 CIV LAIVs to create a bivalent vaccine against both CIV subtypes. Our findings show that, in a mouse model of infection, the bivalent CIV LAIV is safe and able to induce, upon a single intranasal immunization, better protection than that induced by a bivalent CIV IIV against subsequent challenge with H3N8 or H3N2 CIVs. These protection results also correlated with the ability of the bivalent CIV LAIV to induce better humoral immune responses. This is the first description of a bivalent LAIV for the control and prevention of H3N8 and H3N2 CIV infections in dogs.

A live-attenuated influenza vaccine for H3N2 canine influenza virus

Canine influenza is a contagious respiratory disease in dogs caused by two subtypes (H3N2 and H3N8) of canine influenza virus (CIV). Currently, only inactivated influenza vaccines (IIVs) are available for the prevention of CIVs. Historically, live-attenuated influenza vaccines (LAIVs) have been shown to produce better immunogenicity and protection efficacy than IIVs. Here, we have engineered a CIV H3N2 LAIV by using the internal genes of a previously described CIV H3N8 LAIV as a master donor virus (MDV) and the surface HA and NA genes of a circulating CIV H3N2 strain. Our findings show that CIV H3N2 LAIV replicates efficiently at low temperature but its replication is impaired at higher temperatures. The CIV H3N2 LAIV was attenuated in vivo but induced better protection efficacy in mice against challenge with wild-type CIV H3N2 than a commercial CIV H3N2 IIV. This is the first description of a LAIV for the prevention of CIV H3N2 in dogs.

A Multiplex RT-PCR Assay for Detection and Differentiation of Avian-Origin Canine H3N2, Equine-Origin H3N8, Human-Origin H3N2, and H1N1/2009 Canine Influenza Viruses

Virological and serological surveys have documented that H1N1/2009, avian-origin canine H3N2 (cH3N2), seasonal human-origin H3N2 (hH3N2), and equine-origin H3N8 influenza viruses are consistently circulating in dogs. In the present study, a multiplex reverse-transcriptase polymerase chain reaction (mRT-PCR) assay was developed for simultaneous detection and differentiation of these influenza viruses. Four primer sets were designed to target the hemagglutinin genes of H1N1/2009, cH3N2, hH3N2, and H3N8 canine influenza viruses (CIVs). This mRT-PCR assay demonstrated high specificity and sensitivity for the four CIV subtypes. Additionally, mRT-PCR results obtained from 420 clinical samples were consistent with those obtained by the conventional virus isolation method. Our mRT-PCR assay is reliable for clinical diagnosis and rapid identification of CIVs.

Canine influenza viruses with modified NS1 proteins for the development of live-attenuated vaccines

Canine Influenza Virus (CIV) H3N8 is the causative agent of canine influenza, a common and contagious respiratory disease of dogs. Currently, only inactivated influenza vaccines (IIVs) are available for the prevention of CIV H3N8. However, live-attenuated influenza vaccines (LAIVs) are known to provide better immunogenicity and protection efficacy than IIVs. Influenza NS1 is a virulence factor that offers an attractive target for the preparation of attenuated viruses as LAIVs. Here we generated recombinant H3N8 CIVs containing truncated or a deleted NS1 protein to test their potential as LAIVs. All recombinant viruses were attenuated in mice and showed reduced replication in cultured canine tracheal explants, but were able to confer complete protection against challenge with wild-type CIV H3N8 after a single intranasal immunization. Immunogenicity and protection efficacy was better than that observed with an IIV. This is the first description of a LAIV for the prevention of H3N8 CIV in dogs.

A Novel Vaccination Strategy Mediating the Induction of Lung-Resident Memory CD8 T Cells Confers Heterosubtypic Immunity against Future Pandemic Influenza Virus

The currently used vaccine strategy to combat influenza A virus (IAV) aims to provide highly specific immunity to circulating seasonal IAV strains. However, the outbreak of 2009 influenza pandemic highlights the danger in this strategy. In this study, we tested the hypothesis that universal vaccination that offers broader but weaker protection would result in cross protective T cell responses after primary IAV infection, which would subsequently provide protective immunity against future pandemic strains. Specifically, we used tandem repeat extracellular domain of M2 (M2e) epitopes on virus-like particles (M2e5x VLP) that induced heterosubtypic immunity by eliciting Abs to a conserved M2e epitope. M2e5x VLP was found to be superior to strain-specific current split vaccine in conferring heterosubtypic cross protection and in equipping the host with cross-protective lung-resident nucleoprotein-specific memory CD8(+) T cell responses to a subsequent secondary infection with a new pandemic potential strain. Immune correlates for subsequent heterosubtypic immunity by M2e5x VLP vaccination were found to be virus-specific CD8(+) T cells secreting IFN-γ and expressing lung-resident memory phenotypic markers CD69(+) and CD103(+) as well as M2e Abs. Hence, vaccination with M2e5x VLP may be developable as a new strategy to combat future pandemic outbreaks.

Molecular analyses of H3N2 canine influenza viruses isolated from Korea during 2013-2014

Canine influenza A virus (CIV) causes a respiratory disease among dog populations and is prevalent in North America and Asia. Recently, Asian H3N2 CIV infection has been of particular concern, with recent reports related to reassortants with pandemic 2009 strains, direct transmission from a human H3N2, a possibility of H3N2 CIV transmission to other mammals, and even the first outbreak of H3N2 CIVs in North America in April 2015. However, despite these global concerns, our understanding of how influenza A virus transmission impacts the overall populations of H3N2 CIVs remains incomplete. Hence, we investigated the evolutionary history of the most recent two Korean CIV isolates, A/canine/Korea/BD-1/2013 and A/canine/Korea/DG1/2014, along with 57 worldwide CIVs, using comprehensive molecular analyses based on genomic genotyping. This study presents that the new Korean CIV isolates are closely related to the predominantly circulating H3N2 CIVs with genotypes K, G, E, 3B, F, 2D, F, and 1E, carrying several mutations in antigenic and host determinant sites. Also, our findings show that the genome-wide genetic variations within the H3N2 CIVs are low; however, two antigenic protein (HA and NA) analysis demonstrates genetic diversification of the H3N2 CIVs, which evolves independently between Korea and China.

Origins and Evolutionary Dynamics of H3N2 Canine Influenza Virus

Influenza A viruses (IAVs) are maintained mainly in wild birds, and despite frequent spillover infections of avian IAVs into mammals, only a small number of viruses have become established in mammalian hosts. A new H3N2 canine influenza virus (CIV) of avian origin emerged in Asia in the mid-2000s and is now circulating in dog populations of China and South Korea, and possibly in Thailand. The emergence of CIV provides new opportunities for zoonotic infections and interspecies transmission. We examined 14,764 complete IAV genomes together with all CIV genomes publicly available since its first isolation until 2013. We show that CIV may have originated as early as 1999 as a result of segment reassortment among Eurasian and North American avian IAV lineages. We also identified amino acid changes that might have played a role in CIV emergence, some of which have not been previously identified in other cross-species jumps. CIV evolves at a lower rate than H3N2 human influenza viruses do, and viral phylogenies exhibit geographical structure compatible with high levels of local transmission. We detected multiple intrasubtypic and heterosubtypic reassortment events, including the acquisition of the NS segment of an H5N1 avian influenza virus that had previously been overlooked. In sum, our results provide insight into the adaptive changes required by avian viruses to establish themselves in mammals and also highlight the potential role of dogs to act as intermediate hosts in which viruses with zoonotic and/or pandemic potential could originate, particularly with an estimated dog population of ∼ 700 million.

IMPORTANCE

Influenza A viruses circulate in humans and animals. This multihost ecology has important implications, as past pandemics were caused by IAVs carrying gene segments of both human and animal origin. Adaptive evolution is central to cross-species jumps, and this is why understanding the evolutionary processes that shape influenza A virus genomes is key to elucidating the mechanisms underpinning viral emergence. An avian-origin canine influenza virus (CIV) has recently emerged in dogs and is spreading in Asia. We reconstructed the evolutionary history of CIV and show that it originated from both Eurasian and North American avian lineages. We also identified the mutations that might have been responsible for the cross-species jump. Finally, we provide evidence of multiple reassortment events between CIV and other influenza viruses (including an H5N1 avian virus). This is a cause for concern, as there is a large global dog population to which humans are highly exposed.

H3N2 canine influenza virus with the matrix gene from the pandemic A/H1N1 virus: infection dynamics in dogs and ferrets

After an outbreak of pandemic influenza A/H1N1 (pH1N1) virus, we had previously reported the emergence of a recombinant canine influenza virus (CIV) between the pH1N1 virus and the classic H3N2 CIV. Our ongoing routine surveillance isolated another reassortant H3N2 CIV carrying the matrix gene of the pH1N1 virus from 2012. The infection dynamics of this H3N2 CIV variant (CIV/H3N2mv) were investigated in dogs and ferrets via experimental infection and transmission. The CIV/H3N2mv-infected dogs and ferrets produced typical symptoms of respiratory disease, virus shedding, seroconversion, and direct-contact transmissions. Although indirect exposure was not presented for ferrets, CIV/H3N2mv presented higher viral replication in MDCK cells and more efficient transmission was observed in ferrets compared to classic CIV H3N2. This study demonstrates the effect of reassortment of the M gene of pH1N1 in CIV H3N2.

Fc receptor is not required for inducing antibodies but plays a critical role in conferring protection after influenza M2 vaccination

The ectodomain of matrix protein 2 (M2e) of influenza virus is considered a rational target for a universal influenza A vaccine. To better understand M2e immune-mediated protection, Fc receptor common γ chain deficient (FcRγ(-/-) ) and wild-type mice were immunized with a tandem repeat of M2e presented on virus-like particles (M2e5x VLP). Levels of M2e-specific antibodies that were induced in FcRγ(-/-) mice after immunization with M2e5x VLP were similar to those in wild-type mice. In addition, M2e antibodies induced in FcRγ(-/-) mice were found to be equally protective as those induced in wild-type mice. However, M2e5x VLP-immunized FcRγ(-/-) mice were not well protected, as shown by severe weight loss, higher lung viral titres and interleukin-6 inflammatory cytokine production upon influenza virus challenge compared with M2e5x VLP-immunized wild-type mice. Importantly, FcRγ(-/-) mice that were immunized with inactivated influenza virus induced haemagglutination inhibition activity and were well protected without a significant weight loss. Interestingly, interferon-γ-producing CD4 T and CD8 T cells were found to be prevalent in lungs from M2e5x VLP-immunized FcRγ(-/-) mice, which appeared to be correlated with a faster recovery after infection. These results indicate that Fc receptors play a primary role in conferring M2e-specific antibody-mediated protection whereas T cells may contribute to the recovery at later stages of infection.

Infection and pathogenesis of canine, equine, and human influenza viruses in canine tracheas

Influenza A viruses (IAVs) can jump species barriers and occasionally cause epidemics, epizootics, pandemics, and panzootics. Characterizing the infection dynamics at the target tissues of natural hosts is central to understanding the mechanisms that control host range, tropism, and virulence. Canine influenza virus (CIV; H3N8) originated after the transfer of an equine influenza virus (EIV) into dogs. Thus, comparing CIV and EIV isolates provides an opportunity to study the determinants of influenza virus emergence. Here we characterize the replication of canine, equine, and human IAVs in the trachea of the dog, a species to which humans are heavily exposed. We define a phenotype of infection for CIV, which is characterized by high levels of virus replication and extensive tissue damage. CIV was compared to evolutionarily distinct EIVs, and the early EIV isolates showed an impaired ability to infect dog tracheas, while EIVs that circulated near the time of CIV emergence exhibited a CIV-like infection phenotype. Inoculating dog tracheas with various human IAVs (hIAVs) showed that they infected the tracheal epithelium with various efficiencies depending on the virus tested. Finally, we show that reassortant viruses carrying gene segments of CIV and hIAV are viable and that addition of the hemagglutinin (HA) and neuraminidase (NA) of CIV to the 2009 human pandemic virus results in a virus that replicates at high levels and causes significant lesions. This provides important insights into the role of evolution on viral emergence and on the role of HA and NA as determinants of pathogenicity.

IMPORTANCE

Influenza A viruses (IAVs) have entered new host species in recent history, sometimes with devastating consequences. Canine influenza virus (CIV) H3N8 originated from a direct transfer of an equine influenza virus (EIV) in the early 2000s. We studied the infection patterns of IAVs that circulate in dogs or to which dogs are commonly exposed and showed that CIV emergence was likely caused by an adaptive driver, as evolutionarily distinct EIVs display distinct infection phenotypes. We also showed that many human viruses can infect dog tracheas and that reassortment with CIV results in viable viruses. Finally, we showed that the hemagglutinin and neuraminidase of CIV act as virulence factors. Our findings have significant implications because they show that dogs might act as "mixing vessels" in which novel viruses with pandemic potential could emerge and also provide experimental evidence supporting the role of viral evolution in influenza virus emergence.

Household pets and zoonoses

The popularity of having exotic animals as pets is increasing, particularly among children. It is also estimated that approximately 75% of emerging infectious diseases are zoonotic. The implications of these two trends are areas of concern for the public health community. We conducted a review of household pet zoonoses studies. This included a jurisdictional scan of public health agencies in Canada for policies and protocols on household pet zoonoses. Key stakeholder consultations with pet-related zoonoses experts and authors in Canada enhanced the information reviewed. Trends in pet ownership, risks of disease transmission, burden of illness, and current public health practices were examined. As a result, policy and intervention gaps and future opportunities for research and collaboration were identified. Specifically, pets remain as a primary source of numerous reportable and nonreportable diseases and outbreaks for example, salmonellosis, tularaemia, cutaneous larvae migrans, and Human Lymphocytic Chorimeningitis Virus infections. Pet treats and some pet foods were cited as potential sources of zoonotic diseases. Children under 5 years of age and immuno-compromised individuals were noted as potential high-risk groups; and daycares, schools, summer camps, private homes, and acute care and veterinary hospitals were noted as high-risk settings for zoonotic disease transmission. The primary risk factors identified include improper handling of pets and improper hand hygiene. The continued growth of the pet industry will necessitate interventions by public health, veterinary, and regulatory communities to mitigate the impact of pet zoonoses on the public. These interventions should include enhancement of the current surveillance systems, regulations to address existing gaps in the pet food industry, the development of policies and protocols at the provincial and federal levels of government, education of the public regarding the risks associated with the handling of pets, and greater collaboration among the human and animal health sectors.

Serological report of pandemic (H1N1) 2009 infection among cats in northeastern China in 2012-02 and 2013-03

Background

Influenza A virus has a wide range of hosts. It has not only infected human, but also been reported interspecies transmission from humans to other animals, such as pigs, poultry, dogs and cats. However, prevalence of A (H1N1) pdm09 influenza virus infections in cats in northeastern China is unknown. Therefore, the prevalence of A (H1N1) pdm09 influenza virus infections was performed among cats in northeastern China in this study.

Findings

Of all samples in this study, the overall seroprevalence of pandemic (H1N1) 2009 infection in cats was 21% (240/1140). It also showed a higher prevalence rate of pandemic(H1N1) 2009 infection in pet cats (30.6%) than roaming cats (11%) based on NT. In addition, the results also showed a trend of difference in term of species of cats and it was statistically significant.

Conclusions

This is the first survey on the seroprevalence of pandemic (H1N1) 2009 infection among cats in northeastern China. This study has observed a relatively high seroprevalence of pandemic (H1N1) 2009 among different cat populations in northeastern China, similar seroprevalence studies should be conducted elsewhere.

Evidence for subclinical influenza A(H1N1)pdm09 virus infection among dogs in Guangdong Province, China

During 2012, we identified sampled dogs with elevated levels of antibodies (≥1:40) against A(H1N1)pdm09 virus by using a hemagglutination inhibition (HI) assay (seroprevalence, 24.7%) and a microneutralization (MN) assay (seroprevalence, 10.8%). These high seroprevalences of A(H1N1)pdm09 among dogs without clinical signs of influenza support the premise that dogs may play a role in the human influenza ecology in China.

Evolution and ecology of influenza A viruses

Wild aquatic bird populations have long been considered the natural reservoir for influenza A viruses with virus transmission from these birds seeding other avian and mammalian hosts. While most evidence still supports this dogma, recent studies in bats have suggested other reservoir species may also exist. Extensive surveillance studies coupled with an enhanced awareness in response to H5N1 and pandemic 2009 H1N1 outbreaks is also revealing a growing list of animals susceptible to infection with influenza A viruses. Although in a relatively stable host-pathogen interaction in aquatic birds, antigenic, and genetic evolution of influenza A viruses often accompanies interspecies transmission as the virus adapts to a new host. The evolutionary changes in the new hosts result from a number of processes including mutation, reassortment, and recombination. Depending on host and virus these changes can be accompanied by disease outbreaks impacting wildlife, veterinary, and public health.

PB2-588I enhances 2009 H1N1 pandemic influenza virus virulence by increasing viral replication and exacerbating PB2 inhibition of beta interferon expression

The 2009 pandemic H1N1 influenza virus (pdm/09) is typically mildly virulent in mice. In a previous study, we identified four novel swine isolates of pdm/09 viruses that exhibited high lethality in mice. Comparing the consensus sequences of the PB2 subunit of human isolates of pdm/09 viruses with those of the four swine isolate viruses revealed one consensus mutation: T588I. In this study, we determined that 588T is an amino acid mutation conserved in pdm/09 viruses that was exceedingly rare in previous human influenza isolates. To investigate whether the PB2 with the T5581 mutation (PB2-T558I) has an effect on the increased pathogenicity, we rescued a variant containing PB2-588I (Mex_PB2-588I) in the pdm/09 virus, A/Mexico/4486/2009(H1N1), referred to as Mex_WT (where WT is wild type), and characterized the variant in vitro and in vivo. The results indicated that the mutation significantly enhanced polymerase activity in mammalian cells, and the variant exhibited increased growth properties and induced significant weight loss in a mouse model compared to the wild type. We determined that the mutation exacerbated PB2 inhibition of mitochondrial antiviral signaling protein (MAVS)-mediated beta interferon (IFN-β) expression, and PB2-588I was observed to bind to MAVS more efficiently than PB2-588T. The variant induced lower levels of host IFN-β expression than the WT strain during infection. These findings indicate that the pdm/09 influenza virus has increased pathogenicity upon the acquisition of the PB2-T588I mutation and highlight the need for the continued surveillance of the genetic variation of molecular markers in influenza viruses because of their potential effects on pathogenicity and threats to human health.

No evidence for zoonotic transmission of H3N8 canine influenza virus among US adults occupationally exposed to dogs

OBJECTIVES

The zoonotic potential of H3N8 canine influenza virus (CIV) has not been previously examined; yet considering the popularity of dogs as a companion animal and the zoonotic capabilities of other influenza viruses, the public health implications are great. This study aimed to determine the seroprevalence of antibodies against CIV among a US cohort.

DESIGN

A cross-sectional seroepidemiological study was conducted between 2007 and 2010.

SETTING

Recruitments primarily occurred in Iowa and Florida. Participants were enrolled at dog shows, or at their home or place of employment.

SAMPLE

Three hundred and four adults occupationally exposed to dogs and 101 non-canine-exposed participants completed a questionnaire and provided a blood sample.

MAIN OUTCOME MEASURES

Microneutralization and neuraminidase inhibition assays were performed to detect human sera antibodies against A/Canine/Iowa/13628/2005(H3N8). An enzyme-linked lectin assay (ELLA) was adapted to detect antibodies against a recombinant N8 neuraminidase protein from A/Equine/Pennsylvania/1/2007(H3N8).

RESULTS

For all assays, no significant difference in detectable antibodies was observed when comparing the canine-exposed subjects to the non-canine-exposed subjects.

CONCLUSION

While these results do not provide evidence for cross-species CIV transmission, influenza is predictably unpredictable. People frequently exposed to ill dogs should continually be monitored for novel zoonotic CIV infections.

New and Emerging Pathogens in Canine Infectious Respiratory Disease

Canine infectious respiratory disease is a common, worldwide disease syndrome of multifactorial etiology. This review presents a summary of 6 viruses (canine respiratory coronavirus, canine pneumovirus, canine influenza virus, pantropic canine coronavirus, canine bocavirus, and canine hepacivirus) and 2 bacteria ( Streptococcus zooepidemicus and Mycoplasma cynos) that have been associated with respiratory disease in dogs. For some pathogens a causal role is clear, whereas for others, ongoing research aims to uncover their pathogenesis and contribution to this complex syndrome. Etiology, clinical disease, pathogenesis, and epidemiology are described for each pathogen, with an emphasis on recent discoveries or novel findings.