#18,600
While we think of zoonotic diseases as primarily a threat to humans, the last two pandemics (H1N1 & COVID) - and the rise of HPAI H5 - have demonstrated that companion animals, along with many other species of wildlife, can be equally susceptible to a mammalian adapted virus.
Although this can have grave consequences for the infected animal, it can also provide a novel virus with a new reservoir host - one which may allow it to spread, and evolve - and then spill back into humans.
Until just over 20 years ago, dogs and cats were thought unlikely to be infected with influenza A viruses. That is, until large cats in South East Asian zoos began to die after consuming H5N1 infected poultry, and greyhounds at a racetrack became infected with equine H3N8 (see EID Journal article Influenza A Virus (H3N8) in Dogs with Respiratory Disease, Florida).
Three years later (2007), another avian H3N2 virus jumped from poultry to dogs - this time in South Korea - and after spreading across China for a few years, it began its world tour. It arrived in the United States in 2015 (see CDC’s Key Facts On The New H3N2 Canine Flu).
In 2020, the SARS-CoV-2 virus emerged in China, and while it was exquisitely suited for human transmission, it also quickly found a home in a number of other mammalian species.During the 2009 pandemic we saw scattered reports of dogs and cats infected with the H1N1 virus (see 2012's Companion Animals & Reverse Zoonosis), while in 2016 we saw an outbreak of avian H7N2 in animal shelters in NYC, which infected hundreds of cats, and spilled back into humans.
- In November of that year, our attentions were focused on a mink variant that had successfully jumped back into Denmark's human population (see Denmark SSI: Increased Mink Variant COVID In Human Population - COVID Risk Assessment).
- A few months later, we learned the CDC was Investigating Possible Mink-To-Human Transmission Of SARS-CoV-2 In The United States.
- In late 2021, we saw Two New Reports Find Widespread SARS-CoV-2 In North American Deer.
Since then, dozens of other species have been found capable of hosting the SARS-CoV-2 virus, and the potential for someday seeing a new, mutated, version to spill back into the human population remains (see Nature: Study on Sentinel Hosts for Surveillance of Future COVID-19-like Outbreaks).
We've also looked at a number of studies on the seroprevalence of SARS-CoV-2 in companion animals around the world, including:
While sample sizes, and the percentage of positive tests, may vary between studies, cats appear to be more susceptible to the SARS-CoV-2 virus than dogs, and are more likely to be symptomatic.
Today we've a new report - in a pre-print on the bioRxiv server - from researchers at the CDC, the USDA and Texas AM University, on the active surveillance of companion animals for the SARS-CoV-2 virus during the first two years of COVID.
I've only included the abstract, and conclusion from the 31-page report, so follow the link to read it in its entirety. I'll have a postscript after you return.
Alex Pauvolid-Correa, Edward Davila, Lisa Auckland, Italo B. Zecca, Rachel E Busselman, Wendy Tang, Christopher M. Roundy, Mary Lea Killian, Mia Kim Torchetti, Melinda Jenkins-Moore, Suelee Robbe-Austerman, Kristina Lantz, Katherine Mozingo, Rachel Tell, Ailam Lim, Yao Akpalu, Rebecca S. B. Fischer, Francisco C. Ferreira, Gabriel L. Hamer, Sarah A. Hamerdoi: https://doi.org/10.1101/2025.02.03.636361
Abstract
Households where people have COVID-19 are high risk environments for companion animals that are susceptible to SARS-CoV-2. We sampled 579 pets from 281 households with one or more laboratory-confirmed person with COVID-19 in central Texas from June 2020 to May 2021.Nineteen out of 396 (4.8%) dogs and 21 out of 157 (13.4%) cats were positive for SARS-CoV-2 by RT-qPCR. Additionally, 95/382 (25%) dogs and 52/146 (36%) cats harbored SARS-CoV-2 neutralizing antibodies. Twenty-six companion animals of ten other species were negative.Overall, 164 (29%) pets were positive for SARS-CoV-2 by molecular and/or serological tests; a total of 110 (39%) out of 281 households had at least one animal with active or past SARS-CoV-2 infection. Cats were more likely to be infected by SARS-CoV-2 and had higher endpoint antibody titers than dogs. Through viral isolation from a subset of respiratory swabs, we documented 6 different lineages in dogs and cats, including the B.1.1 lineage in a cat one month prior to the first known human case in the country.We observed animal and human-pet interaction factors associated with higher risk of infection for dogs and cats, such as days after COVID-19 diagnosis and sharing food. Frequency of clinical signs of disease reported by owners of pets with active infections did not differ from uninfected ones, suggesting that not all reported signs are attributed to SARS-CoV-2 infection. Characterizing animal infections using active SARS-CoV-2 surveillance in pets at risk of infection may aid in One Health pandemic prevention, response, and management.
(SNIP)
Conclusion
Pet infections were not uncommon in households where an infected human resided, with roughly 30% of dogs and cats having SARS-CoV-2 infection in 39% of the 281 households sampled. Cats were more likely to be positive by RT-qPCR and by virus neutralization test than dogs.
Given the median number of days elapsed from the day of human COVID-19 diagnosis to sample collection from household pets that ultimately tested RT-qPCR-positive for SARS-CoV 2 was only 6-7 days, we suggest that future pet surveillance studies in such high-risk environments prioritize sample collection within a week of human diagnosis.
Sharing food and sleeping in the same room with infected people were associated with increased risk for companion animal infection in households with people with COVID-19. Therefore, preventive measures including the restriction or at least the reduction of close contact between people with COVID-19 and pets protect pets from SARS-CoV-2 infection.
Despite reports of symptomatic pets testing positive for SARS-CoV-2, our study shows that infected pets were not more likely to have clinical signs than uninfected pets, and so passive surveillance pipelines that rely on testing of symptomatic animals only may be less useful than active surveillance. Additionally, we showed that pets can signal viral lineages contemporaneously present in human populations, sometimes at nearly the same time as the first human reports of distinct lineages, emphasizing that genomic surveillance efforts should also include pets.
Characterizing animal infections using active SARS-CoV-2 surveillance in pets at risk of infection using the One Health approach is a critical step to effectively address pandemic prevention, response, and management.
Officially, the USDA only lists 406 companion animals in the United States with confirmed SARS-CoV-2 infection - but given there are roughly 90 million dogs and 74 million domestic cats in the United States - it is safe to assume that millions were likely infected with COVID.
Similarly, the USDA currently lists 99 domestic cats infected with H5N1, but that number is undoubtedly much higher, even without the virus spreading efficiently among humans.
While studies are limited, we've seen worrisome signs of mammalian adaptations among infected cats (see Emerg. Microbes & Inf.: Marked Neurotropism and Potential Adaptation of H5N1 Clade 2.3.4.4.b Virus in Naturally Infected Domestic Cats).
Understanding how SARS-CoV-2 transited through - and affected - companion animals during the COVID pandemic may help us better understand what H5N1 might be doing today. And if H5 fizzles, there will always be another viral contender on the horizon.
While its roots go back more than 100 years, over the past two decades the importance of `One Health' - the interconnectedness between human, animal, and environmental health - has gained a lot of traction.In 2014, in Emerging zoonotic viral diseases L.-F. Wang (1, 2) * & G. Crameri wrote:
The last 30 years have seen a rise in emerging infectious diseases in humans and of these over 70% are zoonotic (2, 3). Zoonotic infections are not new. They have always featured among the wide range of human diseases and most, e.g. anthrax, tuberculosis, plague, yellow fever and influenza, have come from domestic animals, poultry and livestock. However, with changes in the environment, human behaviour and habitat, increasingly these infections are emerging from wildlife species.
While we spend a lot of time in this blog looking at seemingly arcane topics - like Henipaviruses in Northern Short-Tailed Shrews in Alabama or Chronic Wasting Disease in North American Elk, or HPAI Virus H5N1 in Wild Rats in Egypt - everything is interconnected
And you never know from where the next big public health threat will emerge.
