Natural SARS-CoV-2 Infection in Kept Ferrets, Spain

Distribution of aminopeptidase N coronavirus receptors in the respiratory and digestive tracts of domestic and wild artiodactyls and carnivores

Aminopeptidase N (APN) is a transmembrane protein that mediates the attachment of the spike protein of several clinically important coronaviruses (CoVs) responsible for respiratory and intestinal diseases in animals and humans. To assess the potential for APN-mediated viral tropism, we characterized APN receptor distribution in the respiratory and intestinal tissues of various artiodactyls (cervids, bovids, camelids and suids) and carnivores (canids, felids, mustelids and phocids) using immunohistochemistry. In the lungs, APN expression was limited to artiodactyls, with strong expression in the bronchiolar epithelium and weaker expression in pneumocytes. Nasal turbinate and tracheal samples, where available, showed stronger APN expression in artiodactyls over carnivores. APN was consistently detected on the microvilli of enterocytes in the small intestine across multiple taxa, while the presence in the colon was more variable. Of the animals examined, pig and alpaca consistently expressed the most abundant APN in the upper and lower respiratory tract. In silico evaluation of APN orthologue sequences from humans, artiodactyls and carnivores identified distinct evolutionary relationships. Further in silico binding predictions for alpaca alphacoronavirus and human coronavirus 229E with cognate and heterologous alpaca and human APN revealed substantial overlapping binding footprints with high conservation of amino acid residues, suggesting an evolutionary divergence and subsequent adaptation of a 229E-like or ancestral virus within a non-human animal host. This combined anatomical and in silico approach enhances understanding of host susceptibility, tissue tropism and viral transmission mechanisms in APN-dependent CoVs and has the potential to inform future strategies for disease modelling, surveillance and control.

Assessment of SARS-CoV-2 exposure in exotic pets in Spain

Evidence of SARS-CoV-2 infections in different animal species raises concerns about the potential for animal reservoirs and transmission to humans. Here, we evaluate the exposure of exotic pet species to this virus throughout the early years of the pandemic (2020 - 2022) in southern Spain. A total of 180 exotic pets (126 domestic rabbits, 31 ferrets, and 23 rodents) were analyzed for antibodies against SARS-CoV-2 using two different ELISAs. ELISA-positive sera were subsequently tested for specific neutralizing antibodies (nAbs) using the virus neutralization test (VNT). Only one brown rat (Rattus norvegicus), representing 0.6 % of the total, tested positive by ELISA, yet showed negative result for SARS-CoV-2 nAbs by VNT. Our results suggest a very limited risk of SARS-CoV-2 transmission among humans and sympatric exotic pet species in the study region. However, the virus's potential for interspecies transmission emphasizes the need for ongoing surveillance, especially in settings with frequent human-animal interactions, to avoid potential virus evolution, the emergence of new animal reservoirs, and spillover events.

SARS-CoV-2 infection and transmission via the skin to oro-nasal route with the production of bioaerosols in the ferret model

Direct and indirect transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been attributed to virus survival in droplets, bioaerosols and on fomites including skin and surfaces. Survival of SARS-CoV-2 variants of concern (Alpha, Beta, Gamma, and Delta) on the skin and virus transference following rounds of skin-to-skin contact were assessed on porcine skin as a surrogate for human skin. SARS-CoV-2 variants were detectable on skin by RT-qPCR after 72 h at biologically relevant temperatures (35.2 °C) with viral RNA (vRNA) detected after ten successive skin-to-skin contacts. Skin-to-skin virus transmission to establish infection in ferrets as a model for mild/asymptomatic SARS-CoV-2 infection in mustelids and humans was also investigated and compared to intranasal ferret inoculation. Naïve ferrets exposed to Delta variant SARS-CoV-2 in a 'wet' or 'dry' form on porcine skin resulted in robust infection with shedding detectable for up to 14 days post-exposure, at comparable viral loads to ferrets inoculated intranasally. Transmission of SARS-CoV-2 to naïve ferrets in direct contact with infected ferrets was achieved, with environmental contamination detected from ferret fur swabs and air samples. Genetic substitutions were identified in bioaerosol samples acquired following single contact passage in ferrets, including Spike, ORF1ab, and ORF3a protein sequences, suggesting a utility for monitoring host adaptation and virus evolution via air sampling. The longevity of SARS-CoV-2 variants survival directly on the skin and skin-to-skin transference, enabling subsequent infection via the skin to oro-nasal contact route, could represent a pathway for SARS-CoV-2 infection with implications to public and veterinary health.

Comparative SARS-CoV-2 Omicron BA.5 variant and D614G-Wuhan strain infections in ferrets: insights into attenuation and disease progression during subclinical to mild COVID-19

Introduction

As the SARS-CoV-2 virus continues to evolve and new variants emerge, it becomes crucial to understand the comparative pathological and immunological responses elicited by different strains. This study focuses on the original Wuhan strain and the Omicron variant, which have demonstrated significant differences in clinical outcomes and immune responses.

Methods

We employed ferrets as an experimental model to assess the D614G variant (a derivative of the Wuhan strain) and the Omicron BA.5 variant. Each variant was inoculated into separate groups of ferrets to compare disease severity, viral dissemination, and immune responses.

Results

The D614G variant induced more severe disease and greater viral spread than the Omicron variant. Notably, ferrets infected with the D614G variant exhibited a robust neutralizing antibody response, whereas those infected with the Omicron variant failed to produce a detectable neutralizing antibody response. Despite the clearance of the virus from nearly all tissues by 7 days post-infection, an increase in pathological lesions was observed from 14 to 21 days, particularly in those infected with the D614G variant, suggesting a sustained immune response even after viral clearance.

Discussion

These findings underscore the adaptability of SARS-CoV-2 and illuminate how susceptibility and clinical manifestations vary across different strains and species. The results emphasize the necessity of considering both the direct effects of viral infection and the indirect, often prolonged, impacts of the immune response in evaluating the outcomes of SARS-CoV-2 infections.

Droplet Digital RT-PCR (dd RT-PCR) Detection of SARS-CoV-2 in Honey Bees and Honey Collected in Apiaries across the Campania Region

Coronaviruses (CoVs), a subfamily of Orthocoronavirinae, are viruses that sometimes present a zoonotic character. Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is responsible for the recent outbreak of COVID-19, which, since its outbreak in 2019, has caused about 774,593,066 confirmed cases and 7,028,881 deaths. Aereosols are the main route of transmission among people; however, viral droplets can contaminate surfaces and fomites as well as particulate matter (PM) in suspensions of natural and human origin. Honey bees are well known bioindicators of the presence of pollutants and PMs in the environment as they can collect a great variety of substances during their foraging activities. The aim of this study was to evaluate the possible role of honey bees as bioindicators of the prevalence SARS-CoV-2. In this regard, 91 samples of honey bees and 6 of honey were collected from different apiaries of Campania region (Southern Italy) in four time periods from September 2020 to June 2022 and were analyzed with Droplet Digital RT-PCR for SARS-CoV-2 target genes Orf1b and N. The screening revealed the presence of SARS-CoV-2 in 12/91 in honey bee samples and in 2/6 honey samples. These results suggest that honey bees could also be used as indicators of outbreaks of airborne pathogens such as SARS-CoV-2.

SARS-CoV-2 infection in animals: Patterns, transmission routes, and drivers

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is more widespread in animals than previously thought, and it may be able to infect a wider range of domestic and wild species. To effectively control the spread of the virus and protect animal health, it is crucial to understand the cross-species transmission mechanisms and risk factors of SARS-CoV-2. This article collects published literature on SARS-CoV-2 in animals and examines the distribution, transmission routes, biophysical, and anthropogenic drivers of infected animals. The reported cases of infection in animals are mainly concentrated in South America, North America, and Europe, and species affected include lions, white-tailed deer, pangolins, minks, and cats. Biophysical factors influencing infection of animals with SARS-CoV-2 include environmental determinants, high-risk landscapes, air quality, and susceptibility of different animal species, while anthropogenic factors comprise human behavior, intensive livestock farming, animal markets, and land management. Due to current research gaps and surveillance capacity shortcomings, future mitigation strategies need to be designed from a One Health perspective, with research focused on key regions with significant data gaps in Asia and Africa to understand the drivers, pathways, and spatiotemporal dynamics of interspecies transmission.

Seroprevalence of anti-SARS-CoV-2 antibodies in household domestic ferrets (Mustela putorius furo) in Spain, 2019-2023

SARS-CoV-2 is the causal agent of Coronavirus Disease 2019 (COVID-19) in humans that emerged in late 2019. This virus is able to infect humans and different animal species. Among pets, cats and ferrets are more susceptible to be infected by the SARS-CoV-2. Epidemiological studies are an important tool to provide information under natural conditions of exposure to SARS-CoV-2 virus. In comparison to cats, limited epidemiological studies have been performed in domestic ferrets (Mustela putorius furo) reporting the presence of antibodies in this species. This study analysed the presence of anti-SARS-CoV-2 antibodies in 432 cliend-owned ferrets from different geographical areas of Spain during the different waves of COVID-19 outbreaks from December 2019 to May 2023 (42 months). For this purpose, anti-SARS-CoV-2 antibodies were detected by an enzyme-linked immunosorbent method (ELISA) using the receptor binding domain (RBD) of Spike antigen and confirmed by serum virus neutralization assay. Eighteen of the 432 ferrets included were seroreactive by the in-house ELISA (4.17%, 95% Confidence Interval (CI): 2.65-6.49). In this sense, the wave of COVID-19 with the higher number of seropositive ferrets occurred during the seventh wave when the different Omicron subvariants were the dominant virus variants. Our results suggest that the risk of SARS-CoV-2 transmission in domestic ferrets in natural conditions is low. Further research is need to evaluate the potential risk of transmission of SARS-CoV-2 from human to pets.

Molecular and Serological Studies on Potential SARS-CoV-2 Infection among 43 Lemurs under Human Care-Evidence for Past Infection in at Least One Individual

In the setting of the recent COVID-19 pandemic, transmission of SARS-CoV-2 to animals has been reported in both domestic and wild animals and is a matter of concern. Given the genetic and functional similarities to humans, non-human primates merit particular attention. In the case of lemurs, generally considered endangered, they are believed to be susceptible to SARS-CoV-2 infection. We have conducted a study for evidence of SARS-CoV-2 infection among the 43 lemurs of Mundomar, a zoological park in Benidorm, Spain. They belong to two endangered lemur species, 23 black-and-white ruffed lemurs (Varecia variegata) and 20 ring-tailed lemurs (Lemur catta). Health assessments conducted in 2022 and 2023 included molecular analyses for SARS-CoV-2 RNA of oral and rectal swabs using two different RT-qPCR assays, always with negative results for SARS-CoV-2 in all animals. The assessment also included serological testing for antibodies against the receptor-binding domain (RBD) of the spike protein (S) of SARS-CoV-2, which again yielded negative results in all animals except one black-and-white ruffed lemur, supporting prior infection of that animal with SARS-CoV-2. Our data, while not indicating a high susceptibility of lemurs to SARS-CoV-2 infection, show that they can be infected, adding to the existing information body on potential ways for SARS-CoV-2 virus spreading in zoos, highlighting the need for animal surveillance for the virus.

Fecal-oral transmission of SARS-CoV-2: A systematic review of evidence from epidemiological and experimental studies

BACKGROUND

SARS-CoV-2 ribonucleic acid (RNA) has been detected in feces, but RNA is not infectious. This systematic review aims to answer if fecal SARS-CoV-2 is experimentally infectious and if evidence of human fecal-oral SARS-CoV-2 transmission exists.

METHODS

On September 19, 2022, we searched PubMed, Embase, Web of Science, medRxiv, and bioRxiv. Biomedical studies inoculating SARS-CoV-2 from feces, rectal, or anal swabs in cells, tissue, organoids, or animals were included. Epidemiological studies of groups differing in exposure to fecal SARS-CoV-2 were included. Risk of bias was assessed using standardized tools. Results were summarized by vote counting, tabulation, and a harvest plot. PROSPERO registration no. CRD42020221719.

RESULTS

A total of 4,874 studies were screened; 26 studies were included; and 13 out of 23 biomedical studies (56.5%) succeeded in infection. Two (66.7%) epidemiological studies found limited evidence suggesting fecal-oral transmission. All studies had concerns about the risk of bias.

CONCLUSIONS

It is possible to experimentally infect cell cultures, organoids, and animals with fecal SARS-CoV-2. No strong epidemiologic evidence was found to support human fecal-oral transmission. We advise future research to study fecal infectivity at different time points during infection, apply appropriate controls, use in vivo models, and study fecal exposure as a risk factor of transmission in human populations.

Transmission of severe acute respiratory syndrome coronavirus 2 from humans to animals: is there a risk of novel reservoirs?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a zoonotic virus able to infect humans and multiple nonhuman animal species. Most natural infections in companion, captive zoo, livestock, and wildlife species have been related to a reverse transmission, raising concern about potential generation of animal reservoirs due to human-animal interactions. To date, American mink and white-tailed deer are the only species that led to extensive intraspecies transmission of SARS-CoV-2 after reverse zoonosis, leading to an efficient spread of the virus and subsequent animal-to-human transmission. Viral host adaptations increase the probability of new SARS-CoV-2 variants' emergence that could cause a major global health impact. Therefore, applying the One Health approach is crucial to prevent and overcome future threats for human, animal, and environmental fields.

The panzootic potential of SARS-CoV-2

Each year, SARS-CoV-2 is infecting an increasingly unprecedented number of species. In the present article, we combine mammalian phylogeny with the genetic characteristics of isolates found in mammals to elaborate on the host-range potential of SARS-CoV-2. Infections in nonhuman mammals mirror those of contemporary viral strains circulating in humans, although, in certain species, extensive viral circulation has led to unique genetic signatures. As in other recent studies, we found that the conservation of the ACE2 receptor cannot be considered the sole major determinant of susceptibility. However, we are able to identify major clades and families as candidates for increased surveillance. On the basis of our findings, we argue that the use of the term panzootic could be a more appropriate term than pandemic to describe the ongoing scenario. This term better captures the magnitude of the SARS-CoV-2 host range and would hopefully inspire inclusive policy actions, including systematic screenings, that could better support the management of this worldwide event.

A comprehensive dataset of animal-associated sarbecoviruses

Zoonotic spillover of sarbecoviruses (SarbeCoVs) from non-human animals to humans under natural conditions has led to two large-scale pandemics, the severe acute respiratory syndrome (SARS) pandemic in 2003 and the ongoing COVID-19 pandemic. Knowledge of the genetic diversity, geographical distribution, and host specificity of SarbeCoVs is therefore of interest for pandemic surveillance and origin tracing of SARS-CoV and SARS-CoV-2. This study presents a comprehensive repository of publicly available animal-associated SarbeCoVs, covering 1,535 viruses identified from 63 animal species distributed in 43 countries worldwide (as of February 14,2023). Relevant meta-information, such as host species, sampling time and location, was manually curated and included in the dataset to facilitate further research on the potential patterns of viral diversity and ecological characteristics. In addition, the dataset also provides well-annotated sequence sets of receptor-binding domains (RBDs) and receptor-binding motifs (RBMs) for the scientific community to highlight the potential determinants of successful cross-species transmission that could be aid in risk estimation and strategic design for future emerging infectious disease control and prevention.

Analysis of RBD-ACE2 interactions in livestock species as a factor in the spread of SARS-CoV-2 among animals

The high mutation rate of SARS-CoV-2, which has led to the emergence of a number of virus variants, creates risks of transmission from humans to animal species and the emergence of new animal reservoirs of COVID-19. This study aimed to identify animal species among livestock susceptible to infection and develop an approach that would be possible to use for assessing the hazards caused by new SARS-CoV-2 variants for animals. Bioinformatic analysis was used to evaluate the ability of receptor-binding domains (RBDs) of different SARS-CoV-2 variants to interact with ACE2 receptors of livestock species. The results indicated that the stability of RBD-ACE2 complexes depends on both amino acid residues in the ACE2 sequences of animal species and on mutations in the RBDs of SARS-CoV-2 variants, with the residues in the interface of the RBD-ACE2 complex being the most important. All studied SARS-CoV-2 variants had high affinity for ferret and American mink receptors, while the affinity for horse, donkey, and bird species' receptors significantly increased in the highly mutated Omicron variant. Hazards that future SARS-CoV-2 variants may acquire specificity to new animal species remain high given the mutability of the virus. The continued use and expansion of the bioinformatic approach presented in this study may be relevant for monitoring transmission risks and preventing the emergence of new reservoirs of COVID-19 among animals.

Importance of genomic surveillance of SARS-CoV-2 in cats during reverse zoonosis events: potential viral evolution may occur

The apparition of new variants of severe acute respiratory syndrome coronavirus 2 and lineages is constantly happening because of the high viral mutation rate. Since numerous reverse zoonosis events have been reported so far, genomic surveillance should be conducted in susceptible species to evaluate potential adaptations that may trigger the apparition of new variants. Here, we evaluate the evolution of the infection in a cat naturally infected in parallel with its owner, performing a comparative phylogenetic analysis. Sequencing analysis showed that both were infected with the Omicron BA.5/BF.1 lineage and revealed the presence of nucleotide substitution in the viral genome recovered from the cat with respect to the viral genome from the human sample. This nucleotide substitution (C11897A) produced the amino acid change Orf1a: Q3878K. Therefore, genomic surveillance in the case of reverse zoonosis events is still necessary in order to control possible adaptations of the virus to other susceptible species. IMPORTANCE Genomic surveillance of pets for severe acute respiratory syndrome coronavirus 2 is important to monitor the emergence of new variants of the virus associated with these animals. Pets can serve as a potential reservoir for the virus, and their close contact with humans increases the risk of transmission. By conducting genomic surveillance in pets, it is possible to detect and track new variants early on, allowing for more effective control measures to be put in place. This can help prevent the spread of these variants to human populations and potentially mitigate the impact of the pandemic. Furthermore, it may also provide insight into the evolution and spread of the virus within the animal population.

SARS-CoV-2 Prevalence and Variant Surveillance among Cats in Pittsburgh, Pennsylvania, USA

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infects many mammals, and SARS-CoV-2 circulation in nonhuman animals may increase the risk of novel variant emergence. Cats are highly susceptible to SARS-CoV-2 infection, and there were cases of virus transmission between cats and humans. The objective of this study was to assess the prevalence of SARS-CoV-2 variant infection of cats in an urban setting. We investigated the prevalence of SARS-CoV-2 variant infections in domestic and community cats in the city of Pittsburgh (n = 272). While no cats tested positive for SARS-CoV-2 viral RNA, 35 cats (12.86%) tested SARS-CoV-2-antibody-positive. Further, we compared a cat-specific experimental lateral flow assay (eLFA) and species-agnostic surrogate virus neutralization assay (sVNT) for SARS-CoV-2 antibody detection in cats (n = 71). The eLFA demonstrated 100% specificity compared to sVNT. The eLFA also showed 100% sensitivity for sera with >90% inhibition and 63.63% sensitivity for sera with 40-89% inhibition in sVNT. Using a variant-specific pseudovirus neutralization assay (pVNT) and antigen cartography, we found the presence of antibodies to pre-Omicron and Omicron SARS-CoV-2 variants. Hence, this approach proves valuable in identifying cat exposure to different SARS-CoV-2 variants. Our results highlight the continued exposure of cats to SARS-CoV-2 and warrant coordinated surveillance efforts.

Little Brown Bats (Myotis lucifugus) Support the Binding of SARS-CoV-2 Spike and Are Likely Susceptible to SARS-CoV-2 Infection

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), believed to have originated from a bat species, can infect a wide range of non-human hosts. Bats are known to harbor hundreds of coronaviruses capable of spillover into human populations. Recent studies have shown a significant variation in the susceptibility among bat species to SARS-CoV-2 infection. We show that little brown bats (LBB) express angiotensin-converting enzyme 2 receptor and the transmembrane serine protease 2, which are accessible to and support SARS-CoV-2 binding. All-atom molecular dynamics (MD) simulations revealed that LBB ACE2 formed strong electrostatic interactions with the RBD similar to human and cat ACE2 proteins. In summary, LBBs, a widely distributed North American bat species, could be at risk of SARS-CoV-2 infection and potentially serve as a natural reservoir. Finally, our framework, combining in vitro and in silico methods, is a useful tool to assess the SARS-CoV-2 susceptibility of bats and other animal species.

In silico analysis of ACE2 from different animal species provides new insights into SARS-CoV-2 species spillover

Aim: This study aimed to analyze the phylogenetic relationships between the ACE2 of humans and other animals and investigate the potential interaction between SARS-CoV-2 RBD and ACE2 of different species. Materials & methods: The phylogenetic construction and molecular interactions were assessed using computational models. Results & conclusion: Despite the evolutionary distance, 11 species had a perfect fit for the interaction between their ACE2 and SARS-CoV-2 RBD (Chinchilla lanigera, Neovison vison, Rhinolophus sinicus, Emballonura alecto, Saccopteryx bilineata, Numida meleagris). Among them, the avian N. meleagris was reported for the first time in this study as a probable SARS-CoV-2 host due to the strong molecular interactions. Therefore, predicting potential hosts for SARS-CoV-2 for understanding the epidemiological cycle and proposal of surveillance strategies.

No indication for SARS-CoV-2 transmission to pet ferrets, in five cities in Poland, 2021 - antibody testing among ferrets living with owners infected with SARS-CoV-2 or free of infection

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in China by the end of 2019 and was responsible for a pandemic in the human population that resulted in millions of deaths worldwide. Since the beginning of the pandemic, the role of animals as spill-over or reservoir hosts was discussed. In addition to cats and dogs, ferrets are becoming increasingly popular as companion animals. Under experimental conditions, ferrets are susceptible to SARS-CoV-2 and it appears that they can also be infected through contact with a SARS-CoV-2 positive owner. However, there is still little information available regarding these natural infections. Here, we serologically tested samples collected from pet ferrets (n = 45) from Poland between June and September 2021. Of the ferrets that were included in the study, 29% (13/45) had contact with owners with confirmed SARS-CoV-2 infections. Nevertheless, SARS-CoV-2-specific antibodies could not be detected in any of the animals, independent of the infection status of the owner. The obtained results suggest that ferrets cannot be readily infected with SARS-CoV-2 under natural conditions, even after prolonged contact with infected humans. However, due to the rapid mutation rate of this virus, it is important to include ferrets in future monitoring studies.

SARS-CoV-2 in animals: susceptibility of animal species, risk for animal and public health, monitoring, prevention and control

The epidemiological situation of SARS-CoV-2 in humans and animals is continually evolving. To date, animal species known to transmit SARS-CoV-2 are American mink, raccoon dog, cat, ferret, hamster, house mouse, Egyptian fruit bat, deer mouse and white-tailed deer. Among farmed animals, American mink have the highest likelihood to become infected from humans or animals and further transmit SARS-CoV-2. In the EU, 44 outbreaks were reported in 2021 in mink farms in seven MSs, while only six in 2022 in two MSs, thus representing a decreasing trend. The introduction of SARS-CoV-2 into mink farms is usually via infected humans; this can be controlled by systematically testing people entering farms and adequate biosecurity. The current most appropriate monitoring approach for mink is the outbreak confirmation based on suspicion, testing dead or clinically sick animals in case of increased mortality or positive farm personnel and the genomic surveillance of virus variants. The genomic analysis of SARS-CoV-2 showed mink-specific clusters with a potential to spill back into the human population. Among companion animals, cats, ferrets and hamsters are those at highest risk of SARS-CoV-2 infection, which most likely originates from an infected human, and which has no or very low impact on virus circulation in the human population. Among wild animals (including zoo animals), mostly carnivores, great apes and white-tailed deer have been reported to be naturally infected by SARS-CoV-2. In the EU, no cases of infected wildlife have been reported so far. Proper disposal of human waste is advised to reduce the risks of spill-over of SARS-CoV-2 to wildlife. Furthermore, contact with wildlife, especially if sick or dead, should be minimised. No specific monitoring for wildlife is recommended apart from testing hunter-harvested animals with clinical signs or found-dead. Bats should be monitored as a natural host of many coronaviruses.

Tissue distribution of angiotensin-converting enzyme 2 (ACE2) receptor in wild animals with a focus on artiodactyls, mustelids and phocids

Natural cases of zooanthroponotic transmission of SARS-CoV-2 to animals have been reported during the COVID-19 pandemic, including to free-ranging white-tailed deer (Odocoileus virginianus) in North America and farmed American mink (Neovison vison) on multiple continents. To understand the potential for angiotensin-converting enzyme 2 (ACE2)-mediated viral tropism we characterised the distribution of ACE2 receptors in the respiratory and intestinal tissues of a selection of wild and semi-domesticated mammals including artiodactyls (cervids, bovids, camelids, suids and hippopotamus), mustelid and phocid species using immunohistochemistry. Expression of the ACE2 receptor was detected in the bronchial or bronchiolar epithelium of several European and Asiatic deer species, Bactrian camel (Camelus bactrianus), European badger (Meles meles), stoat (Mustela erminea), hippopotamus (Hippopotamus amphibious), harbor seal (Phoca vitulina), and hooded seal (Cystophora cristata). Further receptor mapping in the nasal turbinates and trachea revealed sparse ACE2 receptor expression in the mucosal epithelial cells and occasional occurrence in the submucosal glandular epithelium of Western roe deer (Capreolus capreolus), moose (Alces alces alces), and alpaca (Vicunga pacos). Only the European badger and stoat expressed high levels of ACE2 receptor in the nasal mucosal epithelium, which could suggest high susceptibility to ACE2-mediated respiratory infection. Expression of ACE2 receptor in the intestinal cells was ubiquitous across multiple taxa examined. Our results demonstrate the potential for ACE2-mediated viral infection in a selection of wild mammals and highlight the intra-taxon variability of ACE2 receptor expression, which might influence host susceptibility and infection.

SARS-CoV-2 and natural infection in animals

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative agent of the novel coronavirus disease (COVID-19) pandemic, which has caused serious challenges for public health systems worldwide. Due to the close relationship between animals and humans, confirmed transmission from humans to numerous animal species has been reported. Understanding the cross-species transmission of SARS-CoV-2 and the infection and transmission dynamics of SARS-CoV-2 in different animals is crucial to control COVID-19 and protect animal health. In this review, the possible animal origins of SARS-CoV-2 and animal species naturally susceptible to SARS-CoV-2 infection are discussed. Furthermore, this review categorizes the SARS-CoV-2 susceptible animals by families, so as to better understand the relationship between SARS-CoV-2 and animals.

Lack of SARS-CoV-2 RNA evidence in the lungs from wild European polecats (Mustela putorius) from Spain

Data on SARS-CoV-2 infection in wildlife species is limited. The high prevalences found in mustelid species such as free-ranging American minks (Neovison vison) and domestic ferrets (Mustela putorius furo) justify the study of this virus in the closely related autochthonous free-ranging European polecat (Mustela putorius). We analysed lung samples from 48 roadkilled polecats collected when the human infection reached its highest levels in Spain (2020-2021). We did not detect infections by SARS-CoV-2; however, surveillance in wild carnivores and particularly in mustelids is still warranted, due to their susceptibility to this virus.

SARS-CoV-2 and animals, a long story that doesn't have to end now: What we need to learn from the emergence of the Omicron variant

OIE, the world organization for animal health, recently released an update on the state of the art of knowledge regarding SARS-CoV-2 in animals. For farmed animals, ferrets and minks were found to be highly susceptible to the virus and develop symptomatic disease both in natural conditions and in experimental infections. Lagomorphs of the species Oryctolagus cuniculus are indicated as highly susceptible to the virus under experimental conditions, but show no symptoms of the disease and do not transmit the virus between conspecifics, unlike raccoon dogs (Nyctereutes procyonoides), which in addition to being highly susceptible to the virus under experimental conditions, can also transmit the virus between conspecifics. Among felines, the circulation of the virus has reached a level of cases such as sometimes suggests the experimental use of vaccines for human use or treatments with monoclonal antibodies. But even among wild animals, several species (White-tailed deer, Egyptian rousettes, and minks) have now been described as potential natural reservoirs of the virus. This proven circulation of SARS-CoV-2 among animals has not been accompanied by the development of an adequate surveillance system that allows following the evolution of the virus among its natural hosts. This will be all the more relevant as the surveillance system in humans inevitably drops and we move to surveillance by sentinels similar to the human flu virus. The lesson that we can draw from the emergence of Omicron and, more than likely, its animal origin must not be lost, and in this mini-review, we explain why.

Serological survey of SARS-CoV-2 in companion animals in China

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can be transmitted from human to companion animals. The national wide serological surveillance against SARS-CoV-2 was conducted among pet animals, mainly in cats and dogs, 1 year after the first outbreak of COVID-19 in China. All sera were tested for SARS-CoV-2 IgG antibodies using an indirect enzyme linked immunosorbent assay (ELISA) based on the receptor binding domain (RBD) of spike protein. This late survey takes advantage of the short duration of the serological response in these animals to track recent episode of transmission. A total of 20,592 blood samples were obtained from 25 provinces across 7 geographical regions. The overall seroprevalence of SARS-CoV-2 infections in cats was 0.015% (2/13397; 95% confidence intervals (CI): 0.0, 0.1). The virus infections in cats were only detected in Central (Hubei, 0.375%) and Eastern China (Zhejiang, 0.087%) with a seroprevalence estimated at 0.090 and 0.020%, respectively. In dogs, the seroprevalence of SARS-CoV-2 infections was 0.014% (1/7159; 95% CI: 0.0, 0.1) in the entire nation, seropositive samples were limited to Beijing (0.070%) of Northern China with a prevalence of 0.054%. No seropositive cases were discovered in other geographic regions, nor in other companion animals analyzed in this study. These data reveal the circulation of SARS-CoV-2 in companion animals, although transmission of the virus to domestic cats and dogs is low in China, continuous monitoring is helpful for the better understand of the virus transmission status and the effect on animals.

Tick-Borne Rickettsioses in the Iberian Peninsula

Tick-borne rickettsioses (TBR) are caused by obligate, intracellular bacteria of the spotted-fever group (SFG) of the genus Rickettsia (Order Rickettsiales), transmitted by hard ticks. TBR are one of the oldest known vector-borne zoonoses and pose a threat to both human and animal health, as over the years, new SFG Rickettsia spp. have been reported worldwide with the potential to be human pathogens. In Portugal and Spain, the countries that constitute the Iberian Peninsula, reported TB rickettsiae causing human disease include Rickettsia conorii conorii, Rickettsia conorii israelensis, Rickettsia slovaca, Rickettsia raoultii, Candidatus Rickettsia rioja, Rickettsia sibirica mongolitimonae, and Rickettsia monacensis. An allochthonous case of TBR caused by Rickettsia massiliae, described in Spain, points to the need to monitor disease epidemiology, to predict risks of exposure and spread of disease, and taking into account globalization and climate changes. This review aims to provide up-to-date information on the status of TBR in the Iberian Peninsula, as well as to show the importance of a national and international collaborative epidemiology surveillance network, towards monitoring Rickettsia spp. circulation in both Portugal and Spain.

Infectious droplet exposure is an inefficient route for SARS-CoV-2 infection in the ferret model

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19) in humans, has a wide host range, naturally infecting felids, canids, cervids, rodents and mustelids. Transmission of SARS-CoV-2 is universally accepted to occur via contact with contaminated secretions from the respiratory epithelium, either directly or indirectly. Transmission via droplet nuclei, generated from a cough or sneeze, has also been reported in several human and experimental animal scenarios. However, the role of droplet transmission at the human-animal interface remains to be fully elucidated. Here, the ferret infection model was used to investigate the routes of infection for the SARS-CoV-2 beta variant (B.1.351). Ferrets were exposed to droplets containing infectious SARS-CoV-2, ranging between 4 and 106 µm in diameter, simulating larger droplets produced by a cough from an infected person. Following exposure, viral RNA was detected on the fur of ferrets, and was deposited onto environmental surfaces, as well as the fur of ferrets placed in direct contact; SARS-CoV-2 remained infectious on the fur for at least 48 h. Low levels of viral RNA were detected in the nasal washes early post-exposure, yet none of the directly exposed, or direct-contact ferrets, became robustly infected or seroconverted to SARS-CoV-2. In comparison, ferrets intranasally inoculated with the SARS-CoV-2 beta variant became robustly infected, shedding viral RNA and infectious virus from the nasal cavity, with transmission to 75 % of naive ferrets placed in direct contact. These data suggest that larger infectious droplet nuclei and contaminated fur play minor roles in SARS-CoV-2 transmission among mustelids and potentially other companion animals.

SARS-CoV-2 as a Zooanthroponotic Infection: Spillbacks, Secondary Spillovers, and Their Importance

In the midst of a persistent pandemic of a probable zoonotic origin, one needs to constantly evaluate the interplay of SARS-CoV-2 (severe acute respiratory syndrome-related coronavirus-2) with animal populations. Animals can get infected from humans, and certain species, including mink and white-tailed deer, exhibit considerable animal-to-animal transmission resulting in potential endemicity, mutation pressure, and possible secondary spillover to humans. We attempt a comprehensive review of the available data on animal species infected by SARS-CoV-2, as presented in the scientific literature and official reports of relevant organizations. We further evaluate the lessons humans should learn from mink outbreaks, white-tailed deer endemicity, zoo outbreaks, the threat for certain species conservation, the possible implication of rodents in the evolution of novel variants such as Omicron, and the potential role of pets as animal reservoirs of the virus. Finally, we outline the need for a broader approach to the pandemic and epidemics, in general, incorporating the principles of One Health and Planetary Health.

Detection of SARS-CoV-2 in a dog with hemorrhagic diarrhea

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, has infected several animal species, including dogs, presumably via human-to-animal transmission. Most infected dogs reported were asymptomatic, with low viral loads. However, in this case we detected SARS-CoV-2 in a dog from the North African coastal Spanish city of Ceuta presenting hemorrhagic diarrhea, a disease also reported earlier on in an infected dog from the USA.

Case presentation

In early January 2021, a West Highland Terrier pet dog from Ceuta (Spain) presented hemorrhagic diarrhea with negative tests for candidate microbial pathogens. Since the animal was in a household whose members suffered SARS-CoV-2 in December 2020, dog feces were analyzed for SARS-CoV-2, proving positive in a two-tube RT-PCR test, with confirmation by sequencing a 399-nucleotide region of the spike (S) gene. Furthermore, next-generation sequencing (NGS) covered > 90% SARS-CoV-2 genome sequence, allowing to classify it as variant B.1.177. Remarkably, the sequence revealed the Ile402Val substitution in the spike protein (S), of potential concern because it mapped in the receptor binding domain (RBD) that mediates virus interaction with the cell. NGS reads mapping to bacterial genomes showed that the dog fecal microbiome fitted best the characteristic microbiome of dog’s acute hemorrhagic diarrhea.

Conclusion

Our findings exemplify dog infection stemming from the human SARS-CoV-2 pandemic, providing nearly complete-genome sequencing of the virus, which is recognized as belonging to the B.1.177 variant, adding knowledge on variant circulation in a geographic region and period for which there was little viral variant characterization. A single amino acid substitution found in the S protein that could have been of concern is excluded to belong to this category given its rarity and intrinsic nature. The dog’s pathology suggests that SARS-CoV-2 could affect the gastrointestinal tract of the dog.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03453-8.

Detection of SARS-CoV-2 in a free ranging leopard (Panthera pardus fusca) in India

We report an incidence of natural infection of SARS-CoV-2 in free-ranging Indian leopard (Panthera pardus fusca). The case was detected during routine screening. Post-mortem and laboratory examination suggested virus-induced interstitial pneumonia. Viral genome could be detected in various organs including brain, lung, spleen, and lymph nodes by real-time PCR. Whole-genome sequence analysis confirmed infection of Pango lineage B.1.617.2 of SARS-CoV-2. Till now, only Asiatic lions have been reported to be infected by SARS-CoV-2 in India. Infections in animals were detected during peak phase of pandemic and all the cases were captive with close contacts with humans, whereas the present case was observed when human cases were significantly low. No tangible evidence linked to widespread infection in the wild population and the incidence seems to be isolated case. High nucleotide sequence homology with prevailing viruses in humans suggested spillover infection to the animal. This report underlines the need for intensive screening of wild animals for keeping track of the virus evolution and development of carrier status of SARS-CoV-2 among wildlife species.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and humoral responses against different variants of concern in domestic pet animals and stray cats from North-Eastern Spain

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic in humans, is able to infect several domestic, captive and wildlife animal species. Since reverse zoonotic transmission to pets has been demonstrated, it is crucial to determine their role in the epidemiology of the disease to prevent further spillover events and major spread of SARS-CoV-2. In the present study, we determined the presence of virus and the seroprevalence to SARS-CoV-2, as well as the levels of neutralizing antibodies (nAbs) against several variants of concern (VOCs) in pets (cats, dogs and ferrets) and stray cats from North-Eastern of Spain. We confirmed that cats and dogs can be infected by different VOCs of SARS-CoV-2 and, together with ferrets, are able to develop nAbs against the ancestral (B.1), Alpha (B.1.1.7), Beta (B.1.315), Delta (B.1.617.2) and Omicron (BA.1) variants, with lower titres against the latest in dogs and cats, but not in ferrets. Although the prevalence of active SARS-CoV-2 infection measured as direct viral RNA detection was low (0.3%), presence of nAbs in pets living in COVID-19-positive households was relatively high (close to 25% in cats, 10% in dogs and 40% in ferrets). It is essential to continue monitoring SARS-CoV-2 infections in these animals due to their frequent contact with human populations, and we cannot discard the probability of a higher animal susceptibility to new potential SARS-CoV-2 VOCs.

The Omicron (B.1.1.529) SARS-CoV-2 variant of concern also affects companion animals

The emergence of the Omicron variant (B.1. 1.529) has brought with it an increase in the incidence of SARS-CoV-2 disease. However, there is hardly any data on its incidence in companion animals. We have detected the presence of this new variant in domestic animals (dogs and cats) living with infected owners in Spain. None of the RT-qPCR positive animals (10.13%) presented any clinical signs and the viral loads detected were low. In addition, the shedding of viral RNA lasted a short period of time in the positive animals. Infection with this variant of concern (VOC) was confirmed by RT-qPCR and sequencing. These outcomes suggest a lower virulence of this variant in infected cats and dogs. They also demonstrate the transmission from infected humans to domestic animals and highlight the importance of active surveillance as well as genomic research to detect the presence of VOCs or mutations associated with animal hosts.

No Evidence of SARS-CoV-2 Infection in Wild Mink (Mustela lutreola and Neogale vison) from Northern Spain during the First Two Years of Pandemic

Simple Summary

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causing coronavirus disease-2019 (COVID-19) is a betacoronavirus (β-CoV) closely related to Severe Acute Respiratory Syndrome (SARS-CoV) and the Middle East Respiratory Syndrome Coronavirus (MERS-CoV), which have also caused severe outbreaks of disease in human populations. Human-to-animal transmission events during the COVID-19 pandemic have been documented in several countries. Different animal species have been proven to be susceptible to infection with SARS-CoV-2 both naturally and by experimental infection, including mustelids such as ferrets, otters, and American mink (Neogale vison). In this sense, infected farmed American mink develop respiratory signs associated with viral pneumonia. This study evaluates the presence of SARS-CoV-2 in European mink (Mustela lutreola) and American mink from Spain, by enzyme-linked immunosorbent assay (ELISA) using the receptor binding domain (RBD) of Spike protein antigen in serum samples and/or by RT-qPCR assays in oropharyngeal and rectal swabs. From January 2020 to February 2022, a total of 162 animals (127 European mink and 35 American mink) with no evidence of SARS-CoV-2 infection were included in the study. Of the 126 serum samples analysed by serology, anti-SARS-CoV-2 antibodies were not detected in the mink included in this study. In the same way, SARS-CoV-2 RNA has not been detected in any of the 160 swabs samples analysed by RT-qPCR. This study shows the absence of the wild mink exposure to SARS-CoV-2 in a geographic area seriously affected by COVID-19. With these results, it can be considered that the probability that the virus is circulating in wild mink is low. With this, the risk of virus transmission to humans by this route is also considered improbable.

Abstract

The impact of the SARS-CoV-2 pandemic on wildlife is largely unevaluated, and extended surveillance of animal species is needed to reach a consensus on the role of animals in the emergence and maintenance of SARS-CoV-2. This infection has been detected in farmed and domestic animals and wild animals, mainly in captivity. The interactions or shared resources with wildlife could represent a potential transmission pathway for the SARS-CoV-2 spill over to other wild species and could lead to health consequences or the establishment of new reservoirs in susceptible hosts. This study evaluated the presence of SARS-CoV-2 in European mink (Mustela lutreola) and American mink (Neogale vison) in Spain by enzyme-linked immunosorbent assay (ELISA) using the receptor binding domain (RBD) of Spike antigen in serum samples and/or by RT-qPCR assays in oropharyngeal and rectal swabs. From January 2020 to February 2022, a total of 162 animals (127 European mink and 35 American mink) with no evidence of SARS-CoV-2 infection were included in the study. Antibodies against the SARS-CoV-2 were not found in the serum samples analysed (n = 126), nor was the virus amplified by RT-qPCR (n = 160 swabs). Our results suggest that the potential role of wild mink and the European mink bred in captivity and released to the wild as dispersers of SARS-CoV-2 is so far low. However, wildlife surveillance for early detection of human and animal risks should be continued. In this sense, epidemiological monitoring measures, including serology and molecular analysis, are necessary.

Transmission history of SARS-CoV-2 in humans and white-tailed deer

The emergence of a novel pathogen in a susceptible population can cause rapid spread of infection. High prevalence of SARS-CoV-2 infection in white-tailed deer (Odocoileus virginianus) has been reported in multiple locations, likely resulting from several human-to-deer spillover events followed by deer-to-deer transmission. Knowledge of the risk and direction of SARS-CoV-2 transmission between humans and potential reservoir hosts is essential for effective disease control and prioritisation of interventions. Using genomic data, we reconstruct the transmission history of SARS-CoV-2 in humans and deer, estimate the case finding rate and attempt to infer relative rates of transmission between species. We found no evidence of direct or indirect transmission from deer to human. However, with an estimated case finding rate of only 4.2%, spillback to humans cannot be ruled out. The extensive transmission of SARS-CoV-2 within deer populations and the large number of unsampled cases highlights the need for active surveillance at the human–animal interface.

Differential susceptibility of SARS-CoV-2 in animals: Evidence of ACE2 host receptor distribution in companion animals, livestock and wildlife by immunohistochemical characterisation

Angiotensin converting enzyme 2 (ACE2) is a host cell membrane protein (receptor) that mediates the binding of coronavirus, most notably SARS coronaviruses in the respiratory and gastrointestinal tracts. Although SARS-CoV-2 infection is mainly confined to humans, there have been numerous incidents of spillback (reverse zoonoses) to domestic and captive animals. An absence of information on the spatial distribution of ACE2 in animal tissues limits our understanding of host species susceptibility. Here, we describe the distribution of ACE2 using immunohistochemistry (IHC) on histological sections derived from carnivores, ungulates, primates and chiroptera. Comparison of mink (Neovison vison) and ferret (Mustela putorius furo) respiratory tracts showed substantial differences, demonstrating that ACE2 is present in the lower respiratory tract of mink but not ferrets. The presence of ACE2 in the respiratory tract in some species was much more restricted as indicated by limited immunolabelling in the nasal turbinate, trachea and lungs of cats (Felis catus) and only the nasal turbinate in the golden Syrian hamster (Mesocricetus auratus). In the lungs of other species, ACE2 could be detected on the bronchiolar epithelium of the sheep (Ovis aries), cattle (Bos taurus), European badger (Meles meles), cheetah (Acinonyx jubatus), tiger and lion (Panthera spp.). In addition, ACE2 was present in the nasal mucosa epithelium of the serotine bat (Eptesicus serotinus) but not in pig (Sus scrofa domestica), cattle or sheep. In the intestine, ACE2 immunolabelling was seen on the microvillus of enterocytes (surface of intestine) across various taxa. These results provide anatomical evidence of ACE2 expression in a number of species which will enable further understanding of host susceptibility and tissue tropism of ACE2 receptor-mediated viral infection.

Ferrets are valuable models for SARS-CoV-2 research

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), resulted in an ongoing pandemic with millions of deaths worldwide. Infection of humans can be asymptomatic or result in fever, fatigue, dry cough, dyspnea, and acute respiratory distress syndrome with multiorgan failure in severe cases. The pathogenesis of COVID-19 is not fully understood, and various models employing different species are currently applied. Ferrets can be infected with SARS-CoV-2 and efficiently transmit the virus to contact animals. In contrast to hamsters, ferrets usually show mild disease and viral replication restricted to the upper airways. Most reports have used the intranasal inoculation route, while the intratracheal infection model is not well characterized. Herein, we present clinical, virological, and pathological data from young ferrets intratracheally inoculated with SARS-CoV-2. Infected animals showed no significant clinical signs, and had transient infection with peak viral RNA loads at 4 days postinfection, mild to moderate rhinitis, and pulmonary endothelialitis/vasculitis. Viral antigen was exclusively found in the respiratory epithelium of the nasal cavity, indicating a particular tropism for cells in this location. Viral antigen was associated with epithelial damage and influx of inflammatory cells, including activated neutrophils releasing neutrophil extracellular traps. Scanning electron microscopy of the nasal respiratory mucosa revealed loss of cilia, shedding, and rupture of epithelial cells. The currently established ferret SARS-CoV-2 infection models are comparatively discussed with SARS-CoV-2 pathogenesis in mink, and the advantages and disadvantages of both species as research models for zoonotic betacoronaviruses are highlighted.

Alternatives to animal models and their application in the discovery of species susceptibility to SARS-CoV-2 and other respiratory infectious pathogens: A review

The emergence of the coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inspired rapid research efforts targeting the host range, pathogenesis and transmission mechanisms, and the development of antiviral strategies. Genetically modified mice, rhesus macaques, ferrets, and Syrian golden hamsters have been frequently used in studies of pathogenesis and efficacy of antiviral compounds and vaccines. However, alternatives to in vivo experiments, such as immortalized cell lines, primary respiratory epithelial cells cultured at an air-liquid interface, stem/progenitor cell-derived organoids, or tissue explants, have also been used for isolation of SARS-CoV-2, investigation of cytopathic effects, and pathogen-host interactions. Moreover, initial proof-of-concept studies for testing therapeutic agents can be performed with these tools, showing that animal-sparing cell culture methods could significantly reduce the need for animal models in the future, following the 3R principles of replace, reduce, and refine. So far, only few studies using animal-derived primary cells or tissues have been conducted in SARS-CoV-2 research, although natural infection has been shown to occur in several animal species. Therefore, the need for in-depth investigations on possible interspecies transmission routes and differences in susceptibility to SARS-CoV-2 is urgent. This review gives an overview of studies employing alternative culture systems like primary cell cultures, tissue explants, or organoids for investigations of the pathophysiology and reverse zoonotic potential of SARS-CoV-2 in animals. In addition, future possibilities of SARS-CoV-2 research in animals, including previously neglected methods like the use of precision-cut lung slices, will be outlined.

The past, current and future epidemiological dynamic of SARS-CoV-2

SARS-CoV-2, the agent of the COVID-19 pandemic, emerged in late 2019 in China, and rapidly spread throughout the world to reach all continents. As the virus expanded in its novel human host, viral lineages diversified through the accumulation of around two mutations a month on average. Different viral lineages have replaced each other since the start of the pandemic, with the most successful Alpha, Delta and Omicron variants of concern (VoCs) sequentially sweeping through the world to reach high global prevalence. Neither Alpha nor Delta was characterized by strong immune escape, with their success coming mainly from their higher transmissibility. Omicron is far more prone to immune evasion and spread primarily due to its increased ability to (re-)infect hosts with prior immunity. As host immunity reaches high levels globally through vaccination and prior infection, the epidemic is expected to transition from a pandemic regime to an endemic one where seasonality and waning host immunization are anticipated to become the primary forces shaping future SARS-CoV-2 lineage dynamics. In this review, we consider a body of evidence on the origins, host tropism, epidemiology, genomic and immunogenetic evolution of SARS-CoV-2 including an assessment of other coronaviruses infecting humans. Considering what is known so far, we conclude by delineating scenarios for the future dynamic of SARS-CoV-2, ranging from the good-circulation of a fifth endemic 'common cold' coronavirus of potentially low virulence, the bad-a situation roughly comparable with seasonal flu, and the ugly-extensive diversification into serotypes with long-term high-level endemicity.

First Detection of SARS-CoV-2 B.1.617.2 (Delta) Variant of Concern in a Symptomatic Cat in Spain

Natural and experimental SARS-CoV-2 infection in pets has been widely evidenced since the beginning of the COVID-19 pandemic. Among the numerous affected animals, cats are one of the most susceptible species. However, little is known about viral pathogenicity and transmissibility in the case of variants of concern (VOCs) in animal hosts, such as the B.1.617.2 (Delta) variant first detected in India. Here, we have identified the B.1.617.2 (Delta) VOC in a cat living with a COVID-19 positive owner. The animal presented mild symptoms (sneezing) and a high viral load was detected in the oropharyngeal swab, suggesting that an active infection was occurring in the upper respiratory tract of the cat. Transmission from the owner to the cat occurred despite the human being fully vaccinated against SARS-CoV-2. This study documents the first detection of B.1.165.2 VOC in a cat in Spain and emphasizes the importance of performing active surveillance and genomic investigation on infected animals.

The Finding of the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) in a Wild Eurasian River Otter (Lutra lutra) Highlights the Need for Viral Surveillance in Wild Mustelids

Animals have been involved in the three known outbreaks of severe respiratory syndromes due to coronaviruses (years 2005, 2012, and 2019). The pandemic nature of the SARS-CoV-2 outbreak increases the likelihood of infection from humans of susceptible animal species that, thus, could become secondary viral hosts and even disease reservoirs. We present evidence of spillover infection of wild mustelids by reporting the presence of SARS-CoV-2 in a Eurasian river otter found near a water reservoir in the Valencian Community (Spain). We detected the virus using two different commercial RTqPCR assays on RNA extracted from the nasopharynx (swabbing) and from lung tissue and mediastinal lymph node homogenates. The corresponding samples from two additional otters from distant sites tested negative in identical assays. The diagnosis in the positive otter was confirmed by two-tube RT-PCR assay in which RNA was first retrotranscribed, and then specific regions of the spike (S), nucleocapsid (N), and ORF10 genes were separately amplified from the produced cDNA, followed by electrophoretic visualization and Sanger sequencing. The sequences of the amplified products revealed some non-synonymous changes in the N and ORF10 partial sequences, relative to the consensus sequence. These changes, identified already in human patient samples, point to human origin of the virus, although their specific combination was unique. These findings, together with our previous report of SARS-CoV-2 infection of feral American mink, highlight the need for SARS-CoV-2 surveillance of wild or feral mustelids to evaluate the risk that these animals could become SARS-CoV-2 reservoirs.

Emerging Respiratory Viruses of Cats

In recent years, advances in diagnostics and deep sequencing technologies have led to the identification and characterization of novel viruses in cats as protoparviruses and chaphamaparvoviruses, unveiling the diversity of the feline virome in the respiratory tract. Observational, epidemiological and experimental data are necessary to demonstrate firmly if some viruses are able to cause disease, as this information may be confounded by virus- or host-related factors. Also, in recent years, researchers were able to monitor multiple examples of transmission to felids of viruses with high pathogenic potential, such as the influenza virus strains H5N1, H1N1, H7N2, H5N6 and H3N2, and in the late 2019, the human hypervirulent coronavirus SARS-CoV-2. These findings suggest that the study of viral infections always requires a multi-disciplinary approach inspired by the One Health vision. By reviewing the literature, we provide herewith an update on the emerging viruses identified in cats and their potential association with respiratory disease.

Histopathology and localization of SARS-CoV-2 and its host cell entry receptor ACE2 in tissues from naturally infected US-farmed mink (Neovison vison)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes respiratory disease in mink similar to human COVID-19. We characterized the pathological findings in 72 mink from US farms with SARS-CoV-2 outbreaks, localized SARS-CoV-2 and its host cellular receptor angiotensin-converting enzyme 2 (ACE2) in mink respiratory tissues, and evaluated the utility of various test methods and specimens for SARS-CoV-2 detection in necropsy tissues. Of SARS-CoV-2-positive animals found dead, 74% had bronchiolitis and diffuse alveolar damage (DAD). Of euthanized SARS-CoV-2-positive animals, 72% had only mild interstitial pneumonia or minimal nonspecific lung changes (congestion, edema, macrophages); similar findings were seen in SARS-CoV-2-negative animals. Suppurative rhinitis, lymphocytic perivascular inflammation in the lungs, and lymphocytic infiltrates in other tissues were common in both SARS-CoV-2-positive and SARS-CoV-2-negative animals. In formalin-fixed paraffin-embedded (FFPE) upper respiratory tract (URT) specimens, conventional reverse transcription-polymerase chain reaction (cRT-PCR) was more sensitive than in situ hybridization (ISH) or immunohistochemistry (IHC) for detection of SARS-CoV-2. FFPE lung specimens yielded less detection of virus than FFPE URT specimens by all test methods. By IHC and ISH, virus localized extensively to epithelial cells in the nasal turbinates, and prominently within intact epithelium; olfactory mucosa was mostly spared. The SARS-CoV-2 receptor ACE2 was extensively detected by IHC within turbinate epithelium, with decreased detection in lower respiratory tract epithelium and alveolar macrophages. This study expands on the knowledge of the pathology and pathogenesis of natural SARS-CoV-2 infection in mink and supports their further investigation as a potential animal model of SARS-CoV-2 infection in humans.

SARS CoV-2 infections in animals, two years into the pandemic

In December 2019, several cases of pneumonia caused by a novel coronavirus, later identified as SARS-CoV-2, were detected in the Chinese city of Wuhan. Due to its rapid worldwide spread, on 11 March 2020 the World Health Organization declared a pandemic state. Since this new virus is genetically similar to the coronaviruses of bats, SARS-CoV-2 was hypothesized to have a zoonotic origin. Within a year of the appearance of SARS-CoV-2, several cases of infection were also reported in animals, suggesting human-to-animal and animal-to-animal transmission among mammals. Natural infection has been found in companion animals as well as captive animals such as lions, tigers, and gorillas. Among farm animals, so far, minks have been found to be susceptible to SARS-CoV-2 infection, whereas not all the relevant studies agree on the susceptibility of pigs. Experimental infections have documented the susceptibility to SARS-CoV-2 of further animal species, including mice, hamsters, cats, dogs, ferrets, raccoon dogs, cattle, and non-human primates. Experimental infections have proven crucial for clarifying the role of animals in transmission and developing models for viral pathogenesis and immunotherapy. On the whole, this review aims to update and critically revise the current information on natural and experimental SARS-CoV-2 infections in animals.

SARS-CoV-2 at the human-animal interphase: A review

Since its emergence in China in December 2019, COVID-19 remains the recent leading disease of concern drawing the public health attention globally. The disease is known of viral origin and zoonotic nature originating from animals. However, to date neither the source of the spillover nor the intermediate hosts are identified. Moreover, the public health situation is intermittently aggravated by identification of new animals susceptible to the SARS-CoV-2 infection, potentially replicating the virus and maintaining intra and interspecies spread of the disease. Although the role of a given animal and/or its produce is important to map the disease pattern, continuous efforts should be undertaken to further understand the epidemiology of SARS-CoV-2, a vital step to establish effective disease prevention and control strategy. This manuscript attempted to review updates regarding SARS-CoV-2 infection at the human-animal interface with consideration to postulations on the genetic relatedness and origin of the different SARS-CoV-2 variants isolated from different animal species. Also, the review addresses the possible role of different animal species and their produce in transmission of the disease. Also, the manuscript discussed the contamination potentiality of the virus and its environmental stability. Finally, we reviewed the currently instituted measures to prevent and manage the spread of SARS-CoV-2 infection. The manuscript suggested the One Health based control measures that could prove of value for the near future.

Large-scale study on virological and serological prevalence of SARS-CoV-2 in cats and dogs in Spain

The disease produced by the severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) is currently one of the primary concerns worldwide. Knowing the zoonotic origin of the disease and that several animal species, including dogs and cats, are susceptible to viral infection, it is critical to assess the relevance of pets in this pandemic. Here, we performed a large-scale study on SARS-CoV-2 serological and viral prevalence in cats and dogs in Spain in order to elucidate their role and susceptibility. Samples from animals in contact with COVID-19 positive people and/or compatible symptoms (n = 492), as well as from random animals (n = 1024), were taken. Despite the large number of animals analyzed, only 12 animals (eight dogs and four cats), which represents 0.79% of the total analyzed animals (n = 1516), were positive for viral SARS-CoV-2 RNA detection by reverse transcription quantitative PCR (RT-qPCR) in which viral isolation was possible in four animals. We detected neutralizing antibodies in 34 animals, four of them were also positive for PCR. This study evidences that pets are susceptible to SARS-CoV-2 infection in natural conditions but at a low level, as evidenced by the low percentage of positive animals detected, being infected humans the main source of infection. However, the inclusion of animals in the surveillance of COVID-19 is still recommended.

A One Health strategy for emerging infectious diseases based on the COVID-19 outbreak

Coronavirus disease 2019 (COVID-19) is as an emerging infectious disease (EID) that has caused the worst public health catastrophe of the 21st century thus far. In terms of impact, the COVID-19 pandemic is second only to the Spanish Flu pandemic of 1918 in modern world history. As of 7 September 2021, there have been 220 million confirmed cases of COVID-19 and more than 4.5 million deaths. EIDs pose serious public health and socio-economic risks, and 70% of EIDs originate from wildlife. Preventing development of EIDs such as COVID-19 is a pressing concern. Here, taking the COVID-19 pandemic as an example, we illustrate the disastrous effects of EIDs and assess their emergence and evolution from a One Health perspective. We propose a One Health strategy, centered on ‘moving the gates forward’, for EID prevention and control at the human–animal–environment interface. This strategy may be instructive and provide early warnings of EIDs in the future.

Epidemiological profiling of SARS-CoV-2 with focus on one-health approaches in mitigating COVID-19 pandemic

Of the 1,415 human pathogens identified, 175 are responsible for causing emerging diseases, 132 are zoonotic and majority of the diseases are categorized as emerging or re-emerging. Emerging novel Coronavirus (COVID- 19) is one of them, and it is responsible for causing social and economically critical disease in both humans and animals. This review presents the understanding of epidemiological characteristics of the COVID-19 pandemic related to host, agent, and the environment with transmission and spread of the disease for better prevention of the COVID-19. The inclination of the viruses to spillover between different species and determining the number of the reservoir of coronaviruses in an entirely new host to create infection is of emerging importance. The understanding of disease patterns will potentiate our expertise to alert how, when, and where the potential epidemic will occur. One health approach involves co-operation from all the sectors, including healthcare (medical and veterinary), environmental, pharmaceutical, educational, research, police, and administration, to combat the COVID-19 pandemic and reduce the public health threat.

Natural and Experimental SARS-CoV-2 Infection in Domestic and Wild Animals

SARS-CoV-2 is the etiological agent responsible for the ongoing COVID-19 pandemic, which continues to spread with devastating effects on global health and socioeconomics. The susceptibility of domestic and wild animal species to infection is a critical facet of SARS-CoV-2 ecology, since reverse zoonotic spillover events resulting in SARS-CoV-2 outbreaks in animal populations could result in the establishment of new virus reservoirs. Adaptive mutations in the virus to new animal species could also complicate ongoing mitigation strategies to combat SARS-CoV-2. In addition, animal species susceptible to SARS-CoV-2 infection are essential as standardized preclinical models for the development and efficacy testing of vaccines and therapeutics. In this review, we summarize the current findings regarding the susceptibility of different domestic and wild animal species to experimental SARS-CoV-2 infection and provide detailed descriptions of the clinical disease and transmissibility in these animals. In addition, we outline the documented natural infections in animals that have occurred at the human-animal interface. A comprehensive understanding of animal susceptibility to SARS-CoV-2 is crucial to inform public health, veterinary, and agricultural systems, and to guide environmental policies.

[Covid-19 and the animal world, from a still mysterious origin towards an always unpredictable future]

Although the emergence of Covid-19 in China has not been clearly elucidated, the hypothesis of an animal origin remains the most likely. It is supported by the presence of the horseshoe bat suspected to be the progenitor of SARS-CoV-2 and by the scarcity of pork, due to African swine fever, diverting consumers to exotic animals of breeding sold in the markets. During this pandemic, several animal species were affected by SARS-CoV-2. Sporadic cases were first reported in pets (dogs and cats) infected by their owners, then in large feline species and apes infected in zoos by their nurses. The most significant human-to-animal transmission has occurred in mink farms, especially in the Netherlands and Denmark, requiring the euthanasia of several million animals, with mink in turn having contaminated men and stray or nomadic cats. The study of natural or experimental transmissions of SARS-CoV-2 has made it possible to identify the most receptive animal species: American minks and raccoon dogs, and to a lesser extent stray or nomadic cats, which could become an animal reservoir due to their sensitivity to this virus and their extending prolificacy. The European Commission decided on May 17, 2021 to strengthen the surveillance of SARS-CoV-2 infections in minks and other mustelids, as well as in raccoon dogs, highlighting stressing that the epidemiological assessment of the risk presented by the he appearance of SARS-CoV-2 in these susceptible species was a public health priority.

Natural Transmission and Experimental Models of SARS CoV-2 Infection in Animals

Since the World Health Organization declared COVID-19 a pandemic in March 2020, millions of people have contracted SARS-CoV-2 and died from the infection. Several domestic and wild species have contracted the disease as well. From the beginning, scientists have been working to develop vaccines and establish therapies that can prevent disease development and improve the clinical outcome in infected people. To understand various aspects of viral pathogenesis and infection dynamics and to support preclinical evaluation of vaccines and therapeutics, a diverse number of animal species have been evaluated for use as models of the disease and infection in humans. Here, we discuss natural SARS-CoV-2 infection of domestic and captive wild animals, as well as the susceptibility of several species to experimental infection with this virus.