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About three weeks ago the Microbiology Society published a press release on a (then) upcoming presentation by Dr. Daesub Song at the Microbiology Society Annual Conference earlier this month at ICC Belfast entitled:
Could dogs be the source of a new flu?
(Excerpt)(Continue . . .)
Results from a 10-year study suggest two strains of influenza that could mix and form a dangerous new strain of influenza spread by dogs.
Dr Daesub Song, Associate Professor (Korea University, Republic of Korea) has called for closer monitoring of dogs and other companion animals as they could be a source of novel human influenza strains. He said, “Until now, dogs were considered neglected hosts in the field of flu research. However, after the first report of interspecies transmission, surveillance of flu viruses from companion animals should be further strengthened.”
In the 2000s, several cases of viruses crossing the host barrier were recorded. Most notably, H3N2 bird flu crossed over to dogs and developed into Canine Influenza virus (CIV). Dr Song’s research has found that this H3N2 CIV could combine with H1N1/2009 and form a new influenza virus, called CIVmv.
Almost immediately hyperbolic headlines began to race around the world (a typical example: the UK's Daily Star's Dogs will unleash killer virus on humans and trigger health PANDEMIC, scientists warn) anguishing over this `new' pandemic threat.
Of course none of this is exactly new, or particularly surprising.We've looked at research by Dr. Daesub Song - and many others - on this topic before, and the potential for seeing a novel flu spread by companion animals is considered a very real one.
Influenza A appears to have first jumped species to dogs 15 years ago when an equine H3N8 virus mutated enough to adapt to a canine host, and began to spread among greyhounds at a Florida race track in 2004 (see EID Journal article Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida).
Two years later, and half-way around the world, another (avian-origin) influenza virus (H3N2) would turn up in domestic dogs in Guangdong Province (see Avian-origin H3N2 canine influenza A viruses in Southern China), and spread rapidly across Asia.In the spring of 2015, the Asian H3N2 Canine flu arrived in America's Midwest (see CDC’s Key Facts On The New H3N2 Canine Flu), and has since sparked outbreaks across much of the nation.
While the canine H3N8 virus has remained relatively stable, the avian-origin H3N2 Canine virus appears more promiscuous. In 2011 we looked at a study (by Dr. Song, et al.) on the Interspecies Transmission of Canine H3N2 to domestic cats in Korea.
The authors wrote:
Our study for the first time shows that cats are susceptible to canine influenza H3N2 infection, suggesting that cats may play an intermediate host role in transmitting the H3N2 virus among feline and canine species, which could lead to the endemic establishment of the virus in companion animals.A year later (2012) Dr. Song and company were back with another study (see Interspecies Transmission Of Canine H3N2 In The Laboratory) that looked at laboratory transmission of the canine H3N2 virus to cats, and to (a far lesser degree), ferrets.
Such a scenario raises a public health concern, as the possibility of the emergence of new recombinant feline or canine influenza viruses in companion animals with the potential to act as zoonotic infection cannot be excluded.
In 2014's A Dog & Cat Flu Review, we looked at the history of influenza A infections in dogs, and cats - including H5N1 and H1N1pdm - which included the following examples:
- In late 2012, in China: Avian-Origin Canine H3N2 Prevalence In Farmed Dogs, we saw a study that found more than 12% of farmed dogs tested in Guangdong province carried a strain of canine H3N2 similar to that seen in Korea.
- During the 2009 H1N1 pandemic we saw reports of dogs infected, and in the middle of the last decade we saw several reports indicating that dogs were susceptible to the H5N1 bird flu virus (see Study: Dogs And H5N1).
- Cats, too, were infected during the 2009 H1N1 pandemic (see Companion Animals And Novel H1N1 & EID Journal: Pandemic H1N1 Infection In Cats).
2018
Emerg. Microbes & Inf.: Genetic & Evolutionary Analysis of Emerging Canine H3N22017
Emerg. Microbes & Infect.: Virulence, Transmissibility & Evolution of Canine H3N2 Influenza Viruses
J. Infect. Dis.: Molecular, Antigenic & Pathological Features of Canine H3N2 Influenza
J. Virology: Zoonotic Risk, Pathogenesis, and Transmission of Canine H3N2
EID Journal: Spread of Canine Influenza A(H3N2) Virus, United StatesOur most recent foray into the topic was last November's EID Journal: Canine Influenza Virus A(H3N2) Clade with Antigenic Variation, China, 2016–2017, which described the emergence and rapid spread of an antigenically distinct canine H3N2 virus with signs of additional mammalian adaptation in China.
Given the media's dire presentations earlier this month, I was happy to find this (very brief) oral abstract from Dr. Song's presentation is now online. As you'll see, it is mostly of a review of what we've learned over the past decade, rather than a breaking news piece.I'll have more after the break.
Inter-species transmission of avian influenza virus to dogs: 10 years experience
Authors: Daesub Song1,* , Woonsung Na1 , Minjoo Yeom1
Correspondence: Daesub Song sds1@korea.ac.kr
First Published Online: 08 April 2019, Access Microbiology 1: doi: 10.1099/acmi.ac2019.po0032
This is an open access article published by the Microbiology Society under the Creative Commons Attribution License
Influenza viruses have continuously evolved into multiple mutant strains from several regions, resulting in aggravated endemic or epidemic outbreak conditions. In the 2000s, several outbreaks of inter-species transmission were reported, such as, the avian H3N2 influenza virus that crossed the host barrier to dogs.
The inter-species transmission gave rise to the H3N2 canine influenza virus (CIV) that spread from East Asia to North America. The newly emerged H3N2 CIV was likely to infect to cats; however, ferrets, which had a SA receptor-binding pattern similar to that of humans, were not suitable natural hosts.
In addition to avian-to-dog transmission, the infectivity of pdm H1N1 and seasonal H3N2 viruses in dogs was proven when artificial inoculation of the viruses with active viral shedding in dogs caused pathologic changes in the lungs.
Studies on sero-prevalence and artificial infection suggested the possibility of co-infection of and reassortment between the two viruses in dogs; later, H3N1 and variants of M-variant H3N2 reassortants between pandemic H1N1/2009 and prototype H3N2 CIV were isolated.
Notably, the H3N2 CIV with the matrix gene of the pdm H1N1 virus showed more efficient transmission in ferrets than the classic H3N2 CIV.
These results implied that this primary companion animal, which lives in closer proximity to humans than pigs, might act as a mixing vessel or a source of novel influenza A virus in humans. Our findings emphasized the necessity of intensive monitoring for influenza infection in companion animals for investigating the potential for the emergence of novel human influenza strains.To put things in perspective, we looked at the above mentioned research on a reassorted H3N2 CIV with the matrix gene from H1N1pdm (cite Song, et al.) back in the summer of 2014 (see Canine H3N2 Reassortant With pH1N1 Matrix Gene).
Long time readers may also recall that swine variant influenza in the United States really took off in 2012, after it was discovered to have reassorted with - and acquired the M gene from, H1N1pdm.
`This M gene may confer increased transmissibility to and among humans, compared to other variant influenza viruses.’ – CDC HAN 2012In 2016 Dr. Song followed up with another study on this Canine H3N2/H1N1 reassortment (see Virulence Of A Novel Reassortant Canine H3N2 In Ferret, Dog and Mouse Models) which found `significantly enhanced virulence' in mice infected with these H3N2/H1N1pdm reassortant viruses.
Much of the rapid evolution of canine influenza occurs in China and Southeast Asia, where dogs are still sometimes raised as food, giving them greater exposure to other flu-bearing species such as swine and poultry (see China: Avian-Origin Canine H3N2 Prevalence In Farmed Dogs), and where our visibility is limited.Last summer, however, we saw an eye-opening study in the journal mBio, which found a number of new reassorted canine flu viruses in southern China (see mBio: Novel Reassortant Influenza A Viruses in Canines in Southern China
The authors wrote:
IMPORTANCE
Mammals have emerged as critically under recognized sources of influenza virus diversity, including pigs that were the source of the 2009 pandemic and bats and bovines that harbor highly divergent viral lineages.
Here, we identify two reassortant IAVs that recently host switched from swine to canines in southern China, including one virus with known zoonotic potential. Three additional genotypes were generated via reassortment events in canine hosts, demonstrating the capacity of dogs to serve as “mixing vessels.”
The continued expansion of IAV diversity in canines with high human contact rates requires enhanced surveillance and ongoing evaluation of emerging pandemic threats.
While poultry and swine are the most obvious sources for the next pandemic flu virus, there is ample evidence that other species - including dogs and cats - could be intermediate hosts, and potential `mixing vessels' for an emerging novel flu virus.
If you'd like to read more on this topic, you may wish to revisit:
EID Journal: HPAI H5N6 In Domestic Cats - Korea, 2016
J Infect Dis: Serological Evidence Of H7N2 Infection Among Animal Shelter Workers, NYC 2016
Study: Dogs As Potential `Mixing Vessels’ For Influenza
Virology: Experimental Infection of Peridomestic Animals With Avian H7N9
Influenza A(H6N1) In Dogs, Taiwan
