Following a recent genomics study of the new Coronavirus, and a hypothesis around the role of stray dogs in initiating it, PFMA takes a look at the latest science.
Published on 16 April 2020
By Sarah Hormozi, PFMA Head of Science and Education
On Tuesday 14 April a new study was published in Molecular Biology and Evolution journal, looking at the structure and evolution of SARS-CoV-2 (the virus responsible for COVID-19), in relation to the defence mechanism of its hosts. Several virology experts and professional groups have since provided their critical reviews of the study, and concerns for animal welfare. PFMA reiterates that there is currently no evidence to suggest dogs, or any animals, play a role in the transmission of COVID-19 pandemic. The new hypothetical study underlines the need for more scientific evidence in the search for the origins of this novel disease.
A hypothesis from professor Xuhua Xia (University of Ottawa, Canada) speculating at stray dog intestines as possible origin of SARS-CoV-2
Based on observations of the genetic sequence of a range of coronaviruses, and their hosts, the author of this study has formed a hypothesis on the possible origin and initial transmission of SARS-CoV-2. According to this hypothesis, the ancestor of SARS-CoV-2 entered and infected the digestive system of a mammalian species, such as human or a member of Canidae family, by ingesting bat meat. This was followed by rapid mutation of the virus, leading to reduced CpG (a specific part of viral genome), before entering the respiratory system of the host. This new (reduced CpG) characteristic of the virus allowed it to evade the human immune response and turn into a severe pathogen. The author concludes that more studies are needed to focus on the decreased CpG in the viral genome, and cellular environments that allow for this change. Due to some similarities between a type of canine coronavirus and SARS-CoV-2 (both CpG deficient) the author also highlights the importance of monitoring coronaviruses in feral dogs, to better understand the novel SARS-CoV-2.
What does it mean?
The above study purely forms a theory, based on computer analysis of the genome of a range of coronaviruses, and emphasises on the need for more research in this area. Experts highlight that these theories will need to be further investigated before being proven with new data and robust evidence.
In fact, another recent study, reported in Nature journal on 1 April 2020, looked at susceptibility of a range of species to SARS-CoV-2 and found that dogs are not susceptible to the COVID-19 coronavirus.
As part of a short statement on 15 April, president of the British Veterinary Association (BVA) said: “This research is purely theoretical and the author himself notes that there is no evidence to date of dogs being able to replicate or shed the virus that causes Covid-19. We would urge extreme caution in interpreting it as anything more than a reminder that work is ongoing to consider the origins of the virus.”
A number of expert scientists from across the world have since provided their critical reviews of the study, pointing out its limitations, and the need for more research and new data. Dr Elly Gaunt (University of Edinburgh) as part of her review published on Science Media Centre website, highlighted that the CpG suppression is seen across RNA viruses infecting vertebrates, and across their host vertebrate specie and there is no evidence that dogs are an outlier in terms of the extent of CpG suppression in their genomes. Professor Ben Neuman (Texas A&M University) said: “The conclusion that cats or dogs were involved as an intermediate host for SARS-CoV-2 is highly speculative and should not be presented as fact. It is going to take some new data to finally solve the mystery of the origin of SARS-CoV-2, but this study is based on re-analysis of old data without any new data.” Proffesor James Wood (University of Cambridge) also expressed his views on the conclusions of the study and commented dog owners should not be concerned as a result of this work.
PFMA urges pet owners to follow the official guidance of the UK Government as per previous PFMA statement published on 7 April.