#15,449
Twenty years ago, most veterinarians and influenza researchers believed that dogs and cats were rarely - if ever - infected with human, avian, or swine influenza A viruses. That perception began to change in 2003 when avian HPAI H5N1 began to spill over into cats in Southeast Asia.
The following comes from a World Health Organization GAR report from 2006.H5N1 avian influenza in domestic cats
28 February 2006
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Several published studies have demonstrated H5N1 infection in large cats kept in captivity. In December 2003, two tigers and two leopards, fed on fresh chicken carcasses, died unexpectedly at a zoo in Thailand. Subsequent investigation identified H5N1 in tissue samples.
In February 2004, the virus was detected in a clouded leopard that died at a zoo near Bangkok. A white tiger died from infection with the virus at the same zoo in March 2004.
In October 2004, captive tigers fed on fresh chicken carcasses began dying in large numbers at a zoo in Thailand. Altogether 147 tigers out of 441 died of infection or were euthanized. Subsequent investigation determined that at least some tiger-to-tiger transmission of the virus occurred.
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In 2006, virologist C. A. Nidom of the Institute of Tropical Disease, Airlangga University demonstrated that of 500 cats he tested in and around Jakarta, 20% had antibodies for the H5N1 bird flu virus. Findings that prompted the FAO in 2007 to warn that Avian influenza in cats should be closely monitored.
At roughly the same time (2004), equine H3N8 jumped from horses to dogs at a racetrack in Southern Florida and began to spread globally (see EID Journal article Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida).
Three years after that (2007), a second canine flu virus emerged - this time evolved from an avian H3N2 virus - and began to spread in Asia. (see Transmission of Avian Influenza Virus (H3N2) to Dogs).
Analysis showed that the HA and NA genes of the A/canine/Korea/01/2007 (H3N2) isolate were closely related to those identified in 2003 from chickens and doves in South Korea. Three years later, researchers in South Korea demonstrated that this Canine H3N2 virus could also infect cats (see Korea: Interspecies Transmission of Canine H3N2).
While cats have been more often found to be infected with avian flu viruses (possibly due to their predation of birds and small mammals), both dogs and cats have been infected with Avian H5 viruses (see MAFRA: H5N8 Antibodies Detected In South Korean Dogs (Again)).
Both have also been shown susceptible to humanized influenza viruses, such as the 2009 H1N1 virus (see US: Dog Tests Positive For H1N1), although reports of infected cats have been more common.
Since then, dogs and cats have increasingly been viewed as potential hosts and `mixing vessels' for novel flu viruses. A few (of many) blogs include:
China: Avian-Origin Canine H3N2 Prevalence In Farmed Dogs
Seroprevalence Of Influenza Viruses In Cats - China
Study: Dogs As Potential `Mixing Vessels’ For Influenza
J. Virology: Zoonotic Risk, Pathogenesis, and Transmission of Canine H3N2
Access Microbiology: Inter-Species Transmission of Avian Influenza Virus to Dogs
Perhaps the biggest wake up call came in late 2016 when we saw an avian H7N2 virus sweep through hundreds of cats housed at multiple New York Animal shelters - while also infecting at least two people - demonstrating that that cats can become efficient transmitters of a novel flu virus as well.
With the emergence of COVID-19, we've also discovered that cats (and to a lesser extent, dogs) are susceptible to infection (see MMWR: SARS-CoV-2 Infection in Companion Animals — New York, March–April 2020), although we've seen no compelling evidence that they have transmitted the virus to humans.
Today, however, we have a research article, published in the Journal of Clinical Microbiology, that looks at the seroprevalence of influenza A in both dogs and cats from shelters and homes in the Netherlands.
While it is not surprising that evidence of past 2009 H1N1 infection was found in both dogs and cats, researchers also found evidence of avian H5, H7, and H9 virus exposure in cats and dogs (see chart below).
Virology
Shan Zhao, Nancy Schuurman, Malte Tieke, Berit Quist, Steven Zwinkels, Frank van Kuppeveld, Cornelis A.M. de Haan, Herman EgberinkDOI: 10.1128/JCM.01689-20ABSTRACTInfluenza 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. Besides 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 7 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 (HI) 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/strains. Cat and dog serum samples collected after the 2009 pandemic H1N1 outbreak exhibit much higher seropositivity against H1 compared with 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.
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In conclusion, our findings demonstrate the value of using comprehensive serological assays to analyze antibodies against IAVs and for improved serosurveillance of IAV infections. While we only analyzed cat and dog sera, it will be of interest to analyze what extent these assays will be applicable for serosurveillance of (zoonotic) IAV infections in humans, which is currently particularly being done using HA1 -based assays(53).
Our results indicate that infection of cats and dogs with several subtypes of IAVs is prevalent.
This emphasizes the potential role of both animal species as mixing vessels for IAVs with the possibility of the emergence of mutated/reassorted viruses with increased zoonotic potential. Recurrent epidemiological surveillance for influenza infections among cats and dogs is needed, which could serve as an early cautioning system for human and animal threats.
