Seroprevalence and risk factors for canine H3N8 influenza virus exposure in household dogs in Colorado

Meta-Analysis of Seroprevalence and Prevalence of Influenza A Viruses (Subtypes H3N2, H3N8, and H1N1) in Dogs

Influenza A is a zoonotic disease that affects dogs, pigs, horses, poultry, and birds. In this report, a meta-analysis according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) was conducted. Studies of influenza A viruses in dogs providing prevalence or seroprevalence in any location worldwide were included. The results in this study show that the seroprevalence for the H3N8 influenza subtype was 7.96% (95% CI: 2.03-16.8, p < 0.001), for the H3N2 subtype was 7.44% (95% CI: 4.51-10.5, p < 0.001), and for the H1N1 subtype was 3.10% (95% CI: 0.890-6.01, p < 0.001). In the case of the prevalence analysis, a prevalence of 0.395% (95% CI: 0.160-2.44) for the H3N8 subtype. For the H3N2 subtype, a prevalence of 17.8% (95% CI: 6.66-32.6, p < 0.001) was found. No publication bias was observed in the studies evaluating seroprevalence in the H3N2 and H1N1 subtypes. In the H3N8 subtype, Begg's test indicated publication bias, but Egger's test showed no bias. It is essential to know the approximate prevalence and seroprevalence worldwide of canine influenza, so this study reports the presence of influenza subtypes in dogs, placing this species as a reservoir for human, swine, equine, and avian influenza A viruses.

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.

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.

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.

Prevalence of canine infectious respiratory pathogens in asymptomatic dogs presented at US animal shelters

OBJECTIVES

To determine the prevalence of nine canine infectious respiratory disease (CIRD) pathogens in asymptomatic dogs presented at animal shelters across the United States.

METHODS

Ocular and oronasal swabs from asymptomatic dogs (n = 503) were tested using qPCR assay for Bordetella bronchiseptica, canine adenovirus type 2 (CAV‐2), canine distemper virus (CDV), canine herpesvirus type 1 (CHV), canine influenza virus (CIV), canine parainfluenza virus (CPIV), canine respiratory coronavirus (CRCoV), Mycoplasma cynos and Streptococcus equi subsp zooepidemicus.

RESULTS

A total of 240 (47 · 7%) asymptomatic dogs were PCR‐positive for at least one CIRD pathogen. Prevalence of two‐, three‐, four‐, and five‐pathogen cases was 12 · 7, 3 · 8, 1 · 8, and 0 · 4%, respectively. Mycoplasma cynos (29 · 2%), B. bronchiseptica (19 · 5%), CAV‐2 (12 · 5%), CDV (7 · 4%) and CPIV (3 · 2%) were the most commonly detected pathogens.

CLINICAL SIGNIFICANCE

The prevalence of traditional and newly emerging pathogens associated with CIRD is poorly defined in clinically healthy dogs. This study determined that a high percentage of asymptomatic shelter dogs harbor CIRD pathogens, including the newly emerging pathogen M. cynos and the historically prevalent pathogen B. bronchiseptica.

Contact heterogeneity, rather than transmission efficiency, limits the emergence and spread of canine influenza virus

Host-range shifts in influenza virus are a major risk factor for pandemics. A key question in the study of emerging zoonoses is how the evolution of transmission efficiency interacts with heterogeneity in contact patterns in the new host species, as this interplay influences disease dynamics and prospects for control. Here we use a synergistic mixture of models and data to tease apart the evolutionary and demographic processes controlling a host-range shift in equine H3N8-derived canine influenza virus (CIV). CIV has experienced 15 years of continuous transfer among dogs in the United States, but maintains a patchy distribution, characterized by sporadic short-lived outbreaks coupled with endemic hotspots in large animal shelters. We show that CIV has a high reproductive potential in these facilities (mean R₀ = 3.9) and that these hotspots act as refugia from the sparsely connected majority of the dog population. Intriguingly, CIV has evolved a transmission efficiency that closely matches the minimum required to persist in these refugia, leaving it poised on the extinction/invasion threshold of the host contact network. Corresponding phylogenetic analyses show strong geographic clustering in three US regions, and that the effective reproductive number of the virus (R_e) in the general dog population is close to 1.0. Our results highlight the critical role of host contact structure in CIV dynamics, and show how host contact networks could shape the evolution of pathogen transmission efficiency. Importantly, efficient control measures could eradicate the virus, in turn minimizing the risk of future sustained transmission among companion dogs that could represent a potential new axis to the human-animal interface for influenza.

Influenza virus infects a range of vertebrate hosts, including domesticated animals as well as humans. Some of the most serious influenza pandemics in humans have involved host range shifts, when an influenza virus jumps from one host species to another. Importantly, however, host range shifts do not always cause pandemics. Rather, epidemiological patterns tend to be unpredictable in new host species, causing disease patterns that change over space and time. In this paper, we analyze epidemiological and evolutionary dynamics of canine influenza virus (CIV), which jumped to dogs in the late 1990s from an equine strain (EIV) prevalent in horses. We show that the epidemiology and evolution of CIV is strongly influenced by heterogeneous patterns of infectious contact among dogs in the US. A few large populations in metropolitan animal shelters serve as reservoirs for CIV, but the virus cannot be maintained for long in smaller facilities or in the companion dog population without input from the larger shelters, which represent disease hotspots. These hotspot dynamics give a clear picture of what can happen in the time between the beginning of a host range shift and the onset of a possible pandemic, allowing more targeted strategies for control and eradication.

Evolution of the hemagglutinin gene of H3N8 canine influenza virus in dogs

With the widespread use of a recently developed canine influenza virus (CIV) H3N8 vaccine, continual molecular evaluation of circulating CIVs is necessary for monitoring antigenic drift. The aim of this project was to further describe the genetic evolution of CIV, as well as determine any genetic variation within potential antigenic regions that might result in antigenic drift. To this end, the hemagglutinin gene of 19 CIV isolates from dogs residing in Colorado, New York, and South Carolina humane shelters was sequenced and compared to CIV strains isolated during 2003–2012. Phylogenetic analysis suggests that CIV might be diverging into two geographically distinct lineages. Using a mixed-effects model for evolution and single likelihood ancestor counting methods, several amino acid sites were found to be undergoing selection pressure. Additionally, a total of six amino acid changes were observed in two possible antigenic sites for CIVs isolated from Colorado and New York humane shelters between 2009 and 2011. As CIV isolates might be diverging into geographically distinct lineages, further experiments are warranted to determine the extent of antigenic drift occurring within circulating CIV.

Detection of respiratory viruses and Bordetella bronchiseptica in dogs with acute respiratory tract infections

Canine infectious respiratory disease (CIRD) is an acute, highly contagious disease complex caused by a variety of infectious agents. At present, the role of viral and bacterial components as primary or secondary pathogens in CIRD is not fully understood. The aim of this study was to investigate the prevalence of canine parainfluenza virus (CPIV), canine adenovirus type 2 (CAV-2), canine influenza virus (CIV), canine respiratory coronavirus (CRCoV), canine herpes virus-1 (CHV-1), canine distemper virus (CDV) and Bordetella bronchiseptica in dogs with CIRD and to compare the data with findings in healthy dogs. Sixty-one dogs with CIRD and 90 clinically healthy dogs from Southern Germany were prospectively enrolled in this study. Nasal and pharyngeal swabs were collected from all dogs and were analysed for CPIV, CAV-2, CIV, CRCoV, CHV-1, CDV, and B. bronchiseptica by real-time PCR.

In dogs with acute respiratory signs, 37.7% tested positive for CPIV, 9.8% for CRCoV and 78.7% for B. bronchiseptica. Co-infections with more than one agent were detected in 47.9% of B. bronchiseptica-positive, 82.6% of CPIV-positive, and 100% of CRCoV-positive dogs. In clinically healthy dogs, 1.1% tested positive for CAV-2, 7.8% for CPIV and 45.6% for B. bronchiseptica. CPIV and B. bronchiseptica were detected significantly more often in dogs with CIRD than in clinically healthy dogs (P < 0.001 for each pathogen) and were the most common infectious agents in dogs with CIRD in Southern Germany. Mixed infections with several pathogens were common. In conclusion, clinically healthy dogs can carry respiratory pathogens and could act as sources of infection for susceptible dogs.

Epidemiology and ecology of H3N8 canine influenza viruses in US shelter dogs

BACKGROUND

H3N8 canine influenza virus (CIV) infection might contribute to increased duration of shelter stay for dogs. Greater understanding of factors contributing to CIV within shelters could help veterinarians identify control measures for CIV.

OBJECTIVES

To assess community to shelter dog CIV transmission, estimate true prevalence of CIV, and determine risk factors associated with CIV in humane shelters.

ANIMALS

5,160 dogs upon intake or discharge from 6 US humane shelters, December 2009 through January 2012.

METHODS

A cross-sectional study was performed with prospective convenience sampling of 40 dogs from each shelter monthly. Nasal swabs and serum samples were collected. Hemagglutination inhibition and real-time reverse transcriptase-polymerase chain reaction assays were performed for each nasal and serum sample. True prevalence was estimated by stochastic latent class analysis. Logistic regression was used to identify risk factors associated with CIV shedding and seropositivity.

RESULTS

Nasal swabs were positive from 4.4% of New York (NY), 4.7% of Colorado (CO), 3.2% of South Carolina, 1.2% of Florida, and 0% of California and Texas shelter dogs sampled. Seropositivity was the highest in the CO shelter dogs at 10%, and NY at 8.5%. Other shelters had 0% seropositivity. Information-theoretic analyses suggested that CIV shedding was associated with region, month, and year (model weight = 0.95) and comingling/cohousing (model weight = 0.92).

CONCLUSIONS AND CLINICAL IMPORTANCE

Community dogs are a likely source of CIV introduction into humane shelters and once CIV has become established, dog-to-dog transmission maintains the virus within a shelter.

Evidence of transmission and risk factors for influenza A virus in household dogs and their owners

Background

The possible transmission of influenza A virus between dogs and humans is important, as in Mexico City there are approximately 1·2 million dogs. We present the first evidence of influenza A virus infection in household dogs in Mexico.

Objectives

The objective of this study was to identify the presence of antibodies against influenza A virus in dogs and their owners, as well as the presence of RNA of influenza A virus in nasal exudates of dogs and, thereby, assess the possible transmission of the virus between humans and dogs.

Methods

Serum samples from household dogs and their owners were analyzed to detect the presence of antibodies against three subtypes of human influenza virus (H1N1pdm09, H1N1, and H3N2), as well as subtype H3N8 of equine influenza. We analyzed dog nasal exudates to detect influenza viral RNA. The relationship between the seropositivity of dogs and various factors (age, sex, constantly at home, and seropositivity of owners) was statistically analyzed.

Results

Seroprevalence for human influenza in dogs was 0·9% (1 of 113), and it was 4% (5 of 113) for equine influenza. In humans, seroprevalence was 22% for subtype H1N1pdm09, 20% for subtype H1N1, and 11% for subtype H3N2. No significant association (P > 0·05) was found between seropositivity and any of the assessed factors. Furthermore, no viral RNA was detected in the nasal exudate samples.

Conclusions

Results revealed seroprevalence of the influenza virus in household dogs in Mexico City. It can be assumed that dogs are currently becoming infected with different subtypes of influenza viruses.

Evaluation of virus isolation, one-step real-time reverse transcription polymerase chain reaction assay, and two rapid influenza diagnostic tests for detecting canine Influenza A virus H3N8 shedding in dogs

Sustained transmission of canine Influenza A virus (CIV) H3N8 among U.S. dogs underscores the threat influenza continues to pose to canine health. Because rapid and accurate detection of infection is critical to the diagnosis and control of CIV, the 2 main objectives of the current study were to estimate and compare the sensitivities of CIV testing methods on canine swab samples and to evaluate the performance of Flu Detect™ (Synbiotics Corp., Kansas City, MO) for detecting CIV nasal shedding in high-risk shelter dogs. To address the first objective, nasal and pharyngeal swab samples were collected from 124 shelter and household dogs seen by Colorado State University Veterinary Teaching Hospital clinicians for canine infectious respiratory disease between April 2006 and March 2007 and tested for CIV shedding using virus isolation, the rapid influenza diagnostic test Directigen Flu A+B™ (BD Diagnostic Systems, Sparks, MD), and real-time reverse transcription polymerase chain reaction (RT-PCR). For the second objective, 1,372 dogs with unknown respiratory health status were sampled from 6 U.S. shelters from December 2009 to November 2010. Samples were tested for presence of CIV using real-time RT-PCR and Flu Detect. Using a stochastic latent class modeling approach, the median sensitivities of virus isolation, rapid influenza diagnostic test, and real-time RT-PCR were 72%, 65%, and 95%, respectively. The Flu Detect test performed poorly for detecting CIV nasal shedding compared to real-time RT-PCR. In conclusion, the real-time RT-PCR has the highest sensitivity for detecting virus nasal shedding and can be used as a rapid diagnostic test for CIV.

Diagnostic performance of the canine Influenza A Virus subtype H3N8 hemagglutination inhibition assay

Canine Influenza A virus subtype H3N8 (H3N8 CIV) was recognized in 2004 as a novel respiratory pathogen for dogs. To date, infections have been diagnosed in thousands of dogs in 38 U.S. states. Diagnostic techniques such as reverse transcription polymerase chain reaction (RT-PCR) and virus isolation may yield false-negative results if samples are collected after virus shedding has ceased. Therefore, serology is often necessary to confirm diagnosis. The hemagglutination inhibition (HI) assay is the test of choice for serological diagnosis of influenza infections in animals. However, discrepancies exist between diagnostic laboratories and research groups in some of the test parameters for the H3N8 CIV HI assay and the cutoff antibody titer for seropositivity. The objectives of the current study were 1) to assess the diagnostic performance of a H3N8 CIV HI assay using field sera from canine infectious respiratory disease outbreaks and 2) to evaluate the effect of test parameter variations on test performance, including the use of different red blood cell (RBC) species, serum treatment methods, and virus isolates. Based on a receiver operating characteristic analysis using serum microneutralization assay titers as the gold standard, the H3N8 CIV HI assay described in the present study is highly sensitive (99.6%) and specific (94.6%) when the cutoff antibody titer for seropositivity is 32. Evaluation of parameter variations determined that the sensitivity and specificity of the H3N8 CIV HI assay depend on serum pretreatment with a receptor-destroying enzyme or periodate, use of 0.5% turkey or chicken RBCs, and use of antigenically well-matched H3N8 virus strains.

Serological evidence of H3N8 canine influenza-like virus circulation in USA dogs prior to 2004

H3N8 canine influenza virus (H3N8 CIV) was first reported as a novel canine respiratory pathogen in racing greyhounds and shelter dogs in the U.S.A. in 2004. Phylogenetic analyses determined that this host-adapted pathogen originated from interspecies transmission of an equine influenza virus (EIV), but it is unknown when the transmission occurred prior to discovery in 2004. The objective of this study was to determine if racing greyhound and shelter dog sera collected from 1984 to 2004 had serological evidence of exposure to H3N8 CIV or EIV. Archived sera from 702 racing greyhounds and 1568 shelter dogs were tested for H3 antibodies to the original 2004 CIV isolate, as well as EIV isolates from 1991 to 1999. None of the racing greyhounds from 1984 and 1985 had detectable H3 antibodies. One of the shelter dogs, which entered a north Florida shelter in 2004, was seropositive. For racing greyhounds sampled from 1999 to 2004, 133/520 (26%) dogs had antibodies to both CIV and EIV H3 proteins. The annual seroprevalence was 27% in 1999, 28% in 2000, 10% in 2001, 1% in 2002, 41% in 2003, and 28% in 2004. The odds of H3 seropositivity were greater among dogs that raced > or =6 months, raced on > or =2 tracks, and raced in 1998, 2002, and 2003. Many of the seropositive dogs raced at tracks that were involved in 'kennel cough' epidemics in 1998-1999 and 2002-2003. Based on serological evidence, a H3N8 canine influenza-like virus was circulating in racing greyhounds in the U.S.A. as early as 1999.