SARS-CoV-2 transmission to animals: Monitoring needed to mitigate risk
As evidence mounts for the possibility of SARS-CoV-2 infecting various animals, scientists at UCL say a global effort is needed to reduce the risk of the virus later returning to people.
In a comment piece for The Lancet Microbe, researchers write that if the virus becomes common in an animal population that lives near people, such as pets or livestock, there would be a risk that another outbreak could occur even if the virus is eradicated in people in the area.
The authors call for more research into which animals are susceptible to SARS-CoV-2, the virus causing the Covid-19 disease, and suggest implementing surveillance programmes to regularly test animals that could pose the highest risks of transmission.
Co-author Professor Joanne Santini (UCL Structural & Molecular Biology) said: "There is increasing evidence that some animals can catch SARS-CoV-2 from people, and might subsequently transmit it to other people—but we don't know just how much of a risk this is, as it's an area of study that has not yet been prioritised.
"We need to develop surveillance strategies to ensure we don't get taken by surprise by a large outbreak in animals, which could pose a threat not just to animal health but to human health as well.
"Virus transmission in animal populations could become irreversible if left unchecked, and may threaten the success of existing public health measures if people continue to catch the virus from an infected population of animals."
The authors write that the immense scale of the Covid-19 pandemic compounds the possibility of sufficient animals becoming 'reservoirs' of the virus, which could be more likely than for past epidemics, such as the more contained SARS-CoV-1 outbreak in 2002-2003.
Professor Santini and co-author Professor Sarah Edwards (UCL Science & Technology Studies) reviewed evidence from case studies, experiments testing infection in small groups of animals, as well as laboratory and modelling studies describing likely infection mechanisms.
Modelling and lab studies suggest that SARS-CoV-2 could in theory be transmitted to numerous animals, based on findings that the spike protein on the virus attaches to host cells, using a protein that is found in many different species.
The research paper advises that, once scientists identify which animals could become infected, they then need to figure out whether they will become unwell or remain asymptomatic, and whether an infected individual is able to then transmit the virus to other animals or even to humans.
Notably, there have been recent cases in the Netherlands of farmed mink becoming infected with SARS-CoV-2, leading to two people catching the virus from these animals, in an outbreak that has led to thousands of mink being culled. The researchers say this example highlights not only the risk to human health, but also animal welfare concerns and potential loss of livelihoods in the agricultural sector.
Professor Edwards commented: "There's an urgent need for widespread surveillance, by testing samples, preferably non-invasively, from large numbers of animals, particularly pets, livestock and wildlife that are in close proximity to human populations. More laboratory experiments on small numbers of animals are unlikely to give us the evidence needed to be confident that certain species are entirely safe, making major surveillance work the only real option here.
"We need more information, at the same time as taking simple precautionary measures especially with species which have the potential to spread the virus rapidly in the wild. A robust risk assessment would also require reviewing our ability to manage an outbreak in those animals, namely our ability to isolate, protect, or contain different animals."
More information: The Lancet Microbe, DOI: 10.1016/S2666-5247(20)30069-0