COVID-19 News: US CDC Warns That Peridomestic Animals Such As Deer Mice, Bushy-Tailed Woodrats And Striped Skunks Could Serve As Zoonotic Reservoirs for SARS-CoV-2

COVID-19 News: A new study conducted by researchers from the Colorado State University-USA, and the University of Queensland-Australia has concluded that peridomestic animals such as deer mice, bushy-tailed woodrats and striped skunks could serve as zoonotic reservoirs for the SARS-CoV-2 coronavirus.

The study findings were published in the US Centers for Disease Control and Prevention or CDC’s Emerging Infectious Diseases Journal. https://wwwnc.cdc.gov/eid/article/27/8/21-0180_article
 
Typically zoonosis occurs when a pathogen that derives from animals jumps to, and successfully transmits between, human hosts. But we are now witnessing more cases where humans are passing the virus to not only pets and domestic animals but also to certain wild life.
 
During the early onset of the pandemic, a commonly subscribed to hypothesis was a possible spillover event during close human contact with wild animals at a ‘wet market’ in Wuhan, China, where the virus was first detected in December 2019.
 
Although subsequent phylogenetic evidence has largely problematized this initial thesis, most of the world’s scientific community is still fairly certain that SARS-CoV-2 had jumped to human hosts via wild animals. This was potentially through an intermediary host that contracted the virus from horseshoe bats (a common reservoir for betacoronaviruses like SARS-CoV-2).
 
Past detailed investigations of the types of animals that are susceptible to this type of coronavirus or that can act as zoonotic reservoirs have already been undertaken.
 
These studies have aimed both to try and get closer to understanding the precise origins of the present pandemic, but also to conduct risk assessments on potential future zoonotic spillovers of SARS-CoV-2 so that we may avoid these sorts of calamitous outbreaks in the future. Of particular concern is the virus’s ability to advantageously evolve within animal hosts and then jump back to humans through immunity-evading mutations.
 
However research into how the SARS0CoV-2 coronavirus has affected wildlife species is currently limited. However, this may be crucial to determining whether wildlife species can serve as reservoirs for retaining the virus.
 
This new research attempted to address this issue, peridomestic mammals, which live in and around human habitations, have been investigated to ascertain how SARS-CoV-2 can affect species external to, but in close proximity with, the human population.
 
Typically peridomestic animals may include wild and feral animals which reside near humans and can be seen as a key component for researching the epidemiology of SARS-CoV-2.
 
The critical importance of understanding how SARS-CoV-2 interacts with peridomestic mammals is underscored when assessing their associations with humans and the modification of their habitats due to human intervention. These species are at the highest risk of exposure to the virus from humans, which can be said even in pets such as cats.
 
Furthermore if these species were to be susceptible to the SARS-CoV-2 virus, they may have the capacity to replicate and spread this to a high titer, which ma y lead to the virus being maintained in the species and could result in shedding and being transmitted back into humans. This could possibly lead to an outbreak with new viral variants and populations being led back into a pandemic.
 
It has been known that mammals that can display peridomestic characteristics within urban and suburban environments can include wild rodents, cottontail rabbits, raccoons and striped skunks.
 
Past research has shown these species to shed influenza A viruses after experimental inoculations, suggesting their ability to harbor productive infections when exposed to other human infectious respiratory viruses (like SARS-CoV-2).
 
Detailed protein analyses of amino acid residues of the angiotensin-converting enzyme 2 (ACE2) host cell receptor and the viral spike protein suggest that carnivores and wild rodents are within high-risk groups regarding susceptibility to the virus. However, when investigating which specific species is susceptible to SARS-CoV-2, the research is more complex.
 
It should be noted that rodents are the largest and most diverse order of mammals which makes susceptibility to the virus more varied within the same species. Non-transgenic mice are predominantly found to be unsusceptible to infection.However, transgenic humanized mice and hamsters, as well as Syrian hamsters, are found to be highly susceptible to infections. One previous study found that Roborovki dwarf hamsters exposed to infection resulted in disease and death after three days.
 
The study assessed six common peridomestic rodents for their level of susceptibility to SARS-CoV-2, which included deer mice, wild-caught house mice, bushy-tailed woodrats, fox squirrels, Wyoming ground squirrels, and black-tailed prairie dogs. These animals are commonly found in the United States and have close contact with humans as well as human residences.
 
Another three peridomestic mammals ie cottontail rabbits, raccoons, and striped skunks which may have less interaction with humans but are still commonly found were also assessed.
 
The study findings consisted of illustrating that peridomestic species such as deer mice, bushy-tailed woodrats and striped skunks are susceptible to being infected by SARS-CoV-2 and have the ability to shed the virus in respiratory secretions.
 
Interestingly however, other peridomestic mammals such as cottontail rabbits, fox squirrels, Wyoming ground squirrels, black-tailed prairie dogs, house mice and raccoons were found not to be susceptible to the virus.
 
The peridomestic animals were all assessed daily for the temperament and clinical signs of disease before conclusions were drawn. The results of this study confirm previous research into the susceptibility of animals, such as deer mice. The researchers conclude that most wildlife exposed to the SARS-CoV-2 virus manifest with either no or mild symptoms of the clinical disease. Additionally, they either did not shed the virus or shed the virus for short periods of time.
 
The study team does however acknowledge that while some rodents may be found to be potential reservoirs for the virus, the study has limitations of being unrepresentative due to the high doses provided to the animals.
 
This may not be reflective of reality which relies on the available dose within nature, as this may be lower than what was provided in this study. However, due to the susceptibility of some peridomestic animals, the researchers recommend the development of safety guidelines that can ensure the safety of humans and their pets.
 
This can include risk assessing occupational hazards when working with or around susceptible animals in areas of contact such as barns and sheds. This may require personal protective equipment (PPE) to prevent exposure from any type of pathogen that these rodents may carry. Safety is always of paramount importance, and action should be cautioned when interacting with susceptible animals, especially during the ongoing pandemic.
 
Importantly the study findings has provided insight into how human and wildlife interactions can result in a continual circulation of SARS-CoV-2 in both animals and humans and the likelihood of susceptibility from this interaction.
 
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