Dogs could cause the next big flu outbreak in humans: Deadly new strains of the virus can jump from pets to their owners – and researchers warn we may need a VACCINE to protect us
- Until now, birds and pigs have been the biggest risk for flu transmission to humans
- But dogs are increasingly carrying mutated strains of the virus that affect humans
Dogs could be the carrier of the next deadly flu outbreak among humans, a new study warns.
Until now, pigs and birds have been seen as a bigger disease threat to people, since they can carry diverse types of influenza, while dogs tend to carry canine-specific strains.
But a new report shows the virus is becoming increasingly diversified in domestic dogs, making them prime vectors of disease.
The New York City researchers warn the development could be the tipping point to triggering one of the worst flu outbreaks seen in recent years since humans have much more contact with dogs than with pigs and birds.
Dogs are increasingly carrying mutated strains of the virus that affect humans
‘The majority of pandemics have been associated with pigs as an intermediate host between avian viruses and human hosts,’ said study investigator Adolfo García-Sastre, PhD, of the Icahn School of Medicine at Mt Sinai.
‘In this study, we identified influenza viruses jumping from pigs into dogs.’
The researchers say it is time to think about ways to restrict the circulation of the influenza virus in dogs.
‘The United States is free of avian influenza because every time avian influenza has been detected in poultry in this country, the chickens or turkeys are culled and eliminated from circulation,’ said Dr. García-Sastre.
‘There are attempts to restrict influenza virus in pigs through vaccination and one could consider vaccination for dogs.’
Dr Adolfo Garcia-Sastre, director of the school’s Global Health and Emerging Pathogens Institute, explains that this development stems from a turning point 15 years ago, when researchers documented an influenza virus in a horse jumping into a dog.
That was the first recorded set of circulating canine influenza viruses.
In 2013, researchers found farm dogs in Guangdong, China, carrying a strain of the aggressive H3N2 flu caught from birds.
‘In our study, what we have found is another set of viruses that come from swine that are originally avian in origin, and now they are jumping into dogs and have been reassorted with other viruses in dogs,’ Dr Garcia-Sastre said.
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‘We now have H1N1, H3N2, and H3N8 in dogs. They are starting to interact with each other. This is very reminiscent of what happened in swine ten years before the H1N1 pandemic.’
Influenza can jump among animal reservoirs where many different strains are located.
These reservoirs serve as mixing bowls for the genetic diversity of strains.
Pandemic influenza occurs when viruses jump from animal reservoirs to humans.
With no prior exposure to the virus, most people do not have immunity to these viruses.
The main animal hosts for influenza are wild birds, poultry and other domestic birds in a species pack, as well as pigs and horses.
Some of the viral genes from the 2009 pandemic H1N1 virus originated in birds, from an avian virus that jumped to pigs, exchanged some of its genes with previously circulating swine viruses and then jumped from pigs into humans.
Birds and swine are major reservoirs of viral genetic diversity, whereas equines and canines have historically been restricted to one or two stable influenza A viruses lineages with no or very limited transmission to humans.
In the new study, Dr Garcia-Sastre worked with Dr Martha Nelson a specialist from CRIP, a top flu research group in the US, and Dr Ying Chen, a flu surveillance specialist from China.
They sequenced the complete genomes of 16 influenza viruses from dogs in Southern China between 2013 and 2015.
The viruses in the study were collected primarily from pet dogs presenting with respiratory symptoms at veterinary clinics.
Dogs in certain regions of China, including Guangxi, are also raised for meat and street dogs roam freely, creating a more complex ecosystem for canine influenza virus transmission.
They found a staggering three kinds of swine flu in the genomes – North American triple reassortant H3N2, Eurasian avian-like H1N1, and pandemic H1N1.
One of the H1N1 viruses had mutated with H3N2 viruses, producing three new genotypes of flu – H1N1r, H1N2r, and H3N2r.
‘The new virus we have identified in our study is H1N1, but it comes from swine and is of avian origin, so it is different antigenically from the new H1N1s that were seen in the pandemic and a different origin as the previous H1N1 seen in humans,’ said Dr. García-Sastre.
Future studies will focus on characterizing the virus further and assessing, using human sera, whether humans have existing immunity against canine H1N1 or not.
‘If there is a lot of immunity against these viruses, they will represent less of a risk, but we now have one more host in which influenza virus is starting to have a diverse genotypic and phenotypic characteristics, creating diversity in a host which is in very close contact to humans,’ said Dr García-Sastre.
‘The diversity in dogs has increased so much now that the type of combinations of viruses that can be created in dogs represent potential risk for a virus to jump to a dog into a human.’
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