Transmission of SARS-CoV-2 in Domestic Cats

Ultrafast and high-throughput immunoassay assay to detect anti-SARS-CoV-2 IgG antibodies in dogs and cats

The fact that SARS-CoV-2 has reportedly infected companion, livestock and wildlife animals may constitute a significant risk for virus reservoirs, ground for emerging variants and potential for novel reverse zoonosis. Hence, SARS-CoV-2 surveillance in animal species is crucial to prevent emerging variants which may spread to humans. The present study aimed to develop a simple, high-throughput and ultrafast magnetic bead immunoassay to detect anti-SARS-CoV-2 nucleocapsid and spike reactive IgG antibodies in dog and cat serum samples. The assays were validated using serum from eleven dogs and cats which had SARS-CoV-2 infections confirmed by real-time RT-PCR. The negative cohort consisted of pre-pandemic dog and cat samples. The assays performed at 73-82% sensitivity and 97.5-98% specificity for dogs and 71% sensitivity and 92-94% specificity for cats. The lower assay specificity for cats is explained by the fact that cat pre-pandemic sera showed high levels of cross-reactive with SARS-CoV-2 Nucleocapsid and Spike, supporting that these animals have been exposed to other coronavirus sharing structural similarities with SARS-CoV-2. These assays described in this work are now being used for SARS-CoV-2 surveillance and research purposes.

The comparison of pathogenicity among SARS-CoV-2 variants in domestic cats

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been detected or isolated from domestic cats. It is unclear whether cats play an important role in the SARS-CoV-2 transmission cycle. In this study, we examined the susceptibility of cats to SARS-CoV-2, including wild type and variants, by animal experiments. Cats inoculated with wild type, gamma, and delta variants secreted a large amount of SARS-CoV-2 for 1 week after the inoculation from nasal, oropharyngeal, and rectal routes. Only 100 TCID50 of virus could infect cats and replicate well without severe clinical symptoms. In addition, one cat inoculated with wild type showed persistent virus secretion in feces for over 28 days post-inoculation (dpi). The titer of virus-neutralizing (VN) antibodies against SARS-CoV-2 increased from 11 dpi, reaching a peak at 14 dpi. However, the omicron variant could not replicate well in cat tissues and induced a lower titer of VN antibodies. It is concluded that cats were highly susceptible to SARS-CoV-2 infection, but not to the Omicron Variant, which caused the attenuated pathogenicity.

Surveillance strategies for SARS-CoV-2 infections through one health approach

Coronavirus disease-2019 (COVID-19), caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), is an emergent disease that threatens global health. Public health structures and economic activities have been disrupted globally by the COVID-19 pandemic. Over 556.3 million confirmed cases and 6.3 million deaths have been reported. However, the exact mechanism of its emergence in humans remains unclear. SARS-CoV-2 is believed to have a zoonotic origin, suggesting a spillover route from animals to humans, which is potentially facilitated by wildlife farming and trade. The COVID-19 pandemic highlighted the importance of the One Health approach in managing threats of zoonosis in the human-animal-environment interaction. Implementing vigilant surveillance programs by adopting the One Health concept at the interfaces between wildlife, livestock, and humans is the most pertinent, practical, and actionable strategy for preventing and preparing for future pandemics of zoonosis, such as COVID-19 infection. This review summarizes the updated evidence of CoV infections in humans and animals and provides an appropriate strategy for preventive measures focused on surveillance systems through an On Health approach.

Immunomics in one health: understanding the human, animal, and environmental aspects of COVID-19

The coronavirus disease 2019 (COVID-19) pandemic underscores the critical need to integrate immunomics within the One Health framework to effectively address zoonotic diseases across humans, animals, and environments. Employing advanced high-throughput technologies, this interdisciplinary approach reveals the complex immunological interactions among these systems, enhancing our understanding of immune responses and yielding vital insights into the mechanisms that influence viral spread and host susceptibility. Significant advancements in immunomics have accelerated vaccine development, improved viral mutation tracking, and broadened our comprehension of immune pathways in zoonotic transmissions. This review highlights the role of animals, not merely as carriers or reservoirs, but as essential elements of ecological networks that profoundly influence viral epidemiology. Furthermore, we explore how environmental factors shape immune response patterns across species, influencing viral persistence and spillover risks. Moreover, case studies demonstrating the integration of immunogenomic data within the One Health framework for COVID-19 are discussed, outlining its implications for future research. However, linking humans, animals, and the environment through immunogenomics remains challenging, including the complex management of vast amounts of data and issues of scalability. Despite challenges, integrating immunomics data within the One Health framework significantly enhances our strategies and responses to zoonotic diseases and pandemic threats, marking a crucial direction for future public health breakthroughs.

SARS-CoV-2 Serosurvey of healthy, privately owned cats presenting to a New York City animal hospital in the early phase of the COVID-19 pandemic (2020-2021)

SARS-CoV-2, the cause of the ongoing COVID-19 pandemic, not only infects humans but is also known to infect various species, including domestic and wild animals. While many species have been identified as susceptible to SARS-CoV-2, there are limited studies on the prevalence of SARS-CoV-2 in animals. Both domestic and non-domestic cats are now established to be susceptible to infection by SARS-CoV-2. While serious disease in cats may occur in some instances, the majority of infections appear to be subclinical. Differing prevalence data for SARS-CoV-2 infection of cats have been reported, and are highly context-dependent. Here, we report a retrospective serological survey of cats presented to an animal practice in New York City, located in close proximity to a large medical center that treated the first wave of COVID-19 patients in the U.S. in the Spring of 2020. We sampled 79, mostly indoor, cats between June 2020 to May 2021, the early part of which time the community was under a strict public health "lock-down". Using a highly sensitive and specific fluorescent bead-based multiplex assay, we found an overall prevalence of 13/79 (16%) serologically-positive animals for the study period; however, cats sampled in the Fall of 2020 had a confirmed positive prevalence of 44%. For SARS-CoV-2 seropositive cats, we performed viral neutralization test with live SARS-CoV-2 to additionally confirm presence of SARS-CoV-2 specific antibodies. Of the thirteen seropositive cats, 7/13 (54%) were also positive by virus neutralization, and two of seropositive cats had previously documented respiratory signs, with high neutralization titers of 1/1024 and 1/4096; overall however, there was no statistically significant association of SARS-CoV-2 seropositivity with respiratory signs, or with breed, sex or age of the animals. Follow up sampling of cats showed that positive serological titers were maintained over time. In comparison, we found an overall confirmed positive prevalence of 51% for feline coronavirus (FCoV), an endemic virus of cats, with 30% confirmed negative for FCoV. We demonstrate the impact of SARS-CoV-2 in a defined feline population during the first wave of SARS-CoV-2 infection of humans, and suggest that human-cat transmission was substantial in our study group. Our study provide a new context for SARS-CoV-2 transmission events across species.

Significance

SARS-CoV-2 has a broad animal tropism and can infect a wide range of animal species, leading to an expansion of the viral reservoir. Expansion of this viral reservoir may result in the accumulation of mutations within these species, potentially giving rise to new viral variants and facilitating reverse zoonotic transmission. Domestic cats are particularly noteworthy in this regard due to their close contact with humans. Currently, there are very limited studies on the prevalence of SARS-CoV-2 infection in domestic cats during the early stages of the pandemic, especially in the United States. This retrospective study addresses the gap by investigating seroprevalence of SARS-CoV-2 in cats in New York City, the epicenter of the COVID-19 pandemic in the United States during the early pandemic. Our work underscores the importance of adopting a One Health approach to pandemic prevention and conducting routine surveillance across different animal species.

Mortality associated with SARS-CoV-2 in nondomestic felids

Between September and November 2021, 5 snow leopards (Panthera uncia) and 1 lion (Panthera leo) were naturally infected with severe acute respiratory coronavirus 2 (SARS-CoV-2) and developed progressive respiratory disease that resulted in death. Severe acute respiratory syndrome coronavirus 2 sequencing identified the delta variant in all cases sequenced, which was the predominant human variant at that time. The time between initial clinical signs and death ranged from 3 to 45 days. Gross lesions in all 6 cats included nasal turbinate hyperemia with purulent discharge and marked pulmonary edema. Ulcerative tracheitis and bronchitis were noted in 4 cases. Histologically, there was necrotizing and ulcerative rhinotracheitis and bronchitis with fibrinocellular exudates and fibrinosuppurative to pyogranulomatous bronchopneumonia. The 4 cats that survived longer than 8 days had fungal abscesses. Concurrent bacteria were noted in 4 cases, including those with more acute disease courses. Severe acute respiratory syndrome coronavirus 2 was detected by in situ hybridization using probes against SARS-CoV-2 spike and nucleocapsid genes and by immunohistochemistry. Viral nucleic acid and protein were variably localized to mucosal and glandular epithelial cells, pneumocytes, macrophages, and fibrinocellular debris. Based on established criteria, SARS-CoV-2 was considered a contributing cause of death in all 6 cats. While mild clinical infections are more common, these findings suggest that some SARS-CoV-2 variants may cause more severe disease and that snow leopards may be more severely affected than other felids.

Rapid antigen detection of severe acute respiratory syndrome coronavirus-2 in stray cats: A cross-sectional study

Background and Aim

Although reverse zoonotic transmission events from humans to domestic cats have been described, there is currently little evidence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) circulation in stray cats. Due to the evidence of natural and experimental infections in cats and the capacity to disseminate the virus among them, this study aimed to identify the SARS-CoV-2 antigen in stray cats from the Federal University of Sergipe in Brazil.

Materials and Methods

One hundred twenty six stray cats from the university were screened for SARS-CoV-2 antigens by random sampling. Throat swab samples were tested for the virus using rapid antigen detection tests.

Results

Of the 126 animals tested, 30 (23.60%) were positive for SARS-CoV-2 antigens. To our knowledge, for the first time, this study detected the SARS-CoV-2 antigen in stray cats and confirmed the presence of SARS-CoV-2 infections in Brazil's stray cat population.

Conclusion

The detection of SARS-CoV-2 in stray cats poses a risk for infected and healthy animals and possibly for humans who attend the university daily. As a limitation of the study, the small sample size necessitates caution when interpreting the results. This underscores the need for further research in this area to help control diseases in stray animals during potential pandemics. This highlights the need for monitoring and controlling the spread of the virus in stray animal populations.

Susceptibility and transmissibility of SARS-CoV-2 variants in transgenic mice expressing the cat angiotensin-converting enzyme 2 (ACE-2) receptor

The emergence of SARS-CoV-2 in 2019 and its rapid spread throughout the world has caused the largest pandemic of our modern era. The zoonotic origin of this pathogen highlights the importance of the One Health concept and the need for a coordinated response to this kind of threats. Since its emergence, the virus has caused >7 million deaths worldwide. However, the animal source for human outbreaks remains unknown. The ability of the virus to jump between hosts is facilitated by the presence of the virus receptor, the highly conserved angiotensin-converting enzyme 2 (ACE2), found in various mammals. Positivity for SARS-CoV-2 has been reported in various species, including domestic animals and livestock, but their potential role in bridging viral transmission to humans is still unknown. Additionally, the virus has evolved over the pandemic, resulting in variants with different impacts on human health. Therefore, suitable animal models are crucial to evaluate the susceptibility of different mammalian species to this pathogen and the adaptability of different variants. In this work, we established a transgenic mouse model that expresses the feline ACE2 protein receptor (cACE2) under the human cytokeratin 18 (K18) gene promoter's control, enabling high expression in epithelial cells, which the virus targets. Using this model, we assessed the susceptibility, pathogenicity, and transmission of SARS-CoV-2 variants. Our results show that the sole expression of the cACE2 receptor in these mice makes them susceptible to SARS-CoV-2 variants from the initial pandemic wave but does not enhance susceptibility to omicron variants. Furthermore, we demonstrated efficient contact transmission of SARS-CoV-2 between transgenic mice that express either the feline or the human ACE2 receptor.

The Applications of Nanopore Sequencing Technology in Animal and Human Virus Research

In recent years, an increasing number of viruses have triggered outbreaks that pose a severe threat to both human and animal life, as well as caused substantial economic losses. It is crucial to understand the genomic structure and epidemiology of these viruses to guide effective clinical prevention and treatment strategies. Nanopore sequencing, a third-generation sequencing technology, has been widely used in genomic research since 2014. This technology offers several advantages over traditional methods and next-generation sequencing (NGS), such as the ability to generate ultra-long reads, high efficiency, real-time monitoring and analysis, portability, and the ability to directly sequence RNA or DNA molecules. As a result, it exhibits excellent applicability and flexibility in virus research, including viral detection and surveillance, genome assembly, the discovery of new variants and novel viruses, and the identification of chemical modifications. In this paper, we provide a comprehensive review of the development, principles, advantages, and applications of nanopore sequencing technology in animal and human virus research, aiming to offer fresh perspectives for future studies in this field.

Development of a Targeted NGS Assay for the Detection of Respiratory Pathogens including SARS-CoV-2 in Felines

Acute respiratory diseases in felines can be attributed to a diverse range of pathogens. The recent emergence of novel viruses, particularly SARS-CoV-2 and its variants, has also been associated with respiratory ailments in cats and other pets, underscoring the need for a highly sensitive diagnostic assay capable of concurrently detecting multiple respiratory pathogens. In this study, we developed a targeted next generation sequencing panel using Ion Torrent Ampliseq technology to detect multiple respiratory pathogens, including recent SARS-CoV-2 variants and Feline herpesvirus-1, Feline calicivirus, Bordetella bronchiseptica, Mycoplasmopsis (previously Mycoplasma) felis, and Chlamydia felis. A PCR amplification-based library preparation, employing primers designed for pathogen target regions, was synthesized and divided into two pools, followed by sequencing and assembly to a repertoire of target pathogen genomes. Analytical sensitivity was assessed based on Ct values from real-time PCR for the corresponding pathogens, indicating an equivalent detection limit. Most of the pathogens under study were positively identified to a limit of approximately Ct 36, whereas for Feline herpesvirus-1 and SARS-CoV-2, positive reads were observed in samples with a Ct of 37. Based on a limited number of samples, the diagnostic sensitivity values for the SARS-CoV-2, Feline herpesvirus-1, and M. felis samples were 100% with no false negative results. The diagnostic specificity of SARS-CoV-2, Feline herpesvirus-1, Feline calicivirus, and C. felis were 100%. Importantly, none of the target primers exhibited non-specific amplification, ensuring the absence of false positive results for other pathogens within the study. Additionally, the assay's specificity was validated by cross-referencing the raw sequencing data with established databases like BLAST, affirming the high specificity of the targeted Next-Generation Sequencing (tNGS) assay. Variations in the sequencing reads of different pathogens were observed when subjected to diverse extraction methods. Rigorous assessment of the assay's reliability involved reproducibility across testing personnel and repeated runs. The developed assay's clinical applicability was tested using samples submitted to the diagnostic laboratory from cat shelters and suspected cases. The developed targeted next-generation sequencing methodology empowers the detection of multiple respiratory pathogens manifesting similar clinical symptoms while offering confirmation of results through genome sequencing.

Self-Assembling Sulfated Lactobacillus Exopolysaccharide Nanoparticles as Adjuvants for SARS-CoV-2 Subunit Vaccine Elicit Potent Humoral and Cellular Immune Responses

Coronavirus disease 2019 (COVID-19) has caused a global pandemic since its onset in 2019, and the development of effective vaccines for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to induce potent and long-lasting immunity remains a priority. Herein, we prepared two Lactobacillus exopolysaccharide (EPS) nanoparticle adjuvants (NPs 7-4 and NPs 8-2) that were constructed by using sulfation-modified EPS and quaternization-modified chitosan. These two NPs displayed a spherical morphology with sizes of 39 and 47 nm. Furthermore, the zeta potentials of NPs 7-4 and NPs 8-2 were 50.40 and 44.40 mV, respectively. In vitro assays demonstrated that NPs could effectively adsorb antigenic proteins and exhibited a sustained release effect. Mouse immunization tests showed that the NPs induced the expression of cytokines and chemokines at the injection site and promoted the uptake of antigenic proteins by macrophages. Mechanically, the NPs upregulated the expression of pattern recognition receptors (toll-like receptors and nod-like receptors) and activated the immune response of T cells and the production of neutralizing antibodies. In addition, the NP adjuvants had favorable immune-enhancing effects in cats, which are of great significance for controlling the trans-host transmission and re-endemicity of SARS-CoV-2. Overall, we demonstrated that NP-adjuvanted SARS-CoV-2 receptor binding domain proteins could induce robust specific humoral and cellular immunity.

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.

Mortality associated with SARS-CoV-2 in nondomestic felids

Between September and November 2021, 5 snow leopards ( Panthera uncia) and 1 lion ( Panthera leo) were naturally infected with severe acute respiratory coronavirus 2 (SARS-CoV-2) and developed progressive respiratory disease that resulted in death. Severe acute respiratory syndrome coronavirus 2 sequencing identified the delta variant in all cases sequenced, which was the predominant human variant at that time. The time between initial clinical signs and death ranged from 3 to 45 days. Gross lesions in all 6 cats included nasal turbinate hyperemia with purulent discharge and marked pulmonary edema. Ulcerative tracheitis and bronchitis were noted in 4 cases. Histologically, there was necrotizing and ulcerative rhinotracheitis and bronchitis with fibrinocellular exudates and fibrinosuppurative to pyogranulomatous bronchopneumonia. The 4 cats that survived longer than 8 days had fungal abscesses. Concurrent bacteria were noted in 4 cases, including those with more acute disease courses. Severe acute respiratory syndrome coronavirus 2 was detected by in situ hybridization using probes against SARS-CoV-2 spike and nucleocapsid genes and by immunohistochemistry. Viral nucleic acid and protein were variably localized to mucosal and glandular epithelial cells, pneumocytes, macrophages, and fibrinocellular debris. Based on established criteria, SARS-CoV-2 was considered a contributing cause of death in all 6 cats. While mild clinical infections are more common, these findings suggest that some SARS-CoV-2 variants may cause more severe disease and that snow leopards may be more severely affected than other felids.

ACE2 and TMPRSS2 distribution in the respiratory tract of different animal species and its correlation with SARS-CoV-2 tissue tropism

A wide range of animal species show variable susceptibility to SARS-CoV-2; however, host factors associated with varied susceptibility remain to be defined. Here, we examined whether susceptibility to SARS-CoV-2 and virus tropism in different animal species are dependent on the expression and distribution of the virus receptor angiotensin-converting enzyme 2 (ACE2) and the host cell factor transmembrane serine protease 2 (TMPRSS2). We cataloged the upper and lower respiratory tract of multiple animal species and humans in a tissue-specific manner and quantitatively evaluated the distribution and abundance of ACE2 and TMPRSS2 mRNA in situ. Our results show that: (i) ACE2 and TMPRSS2 mRNA are abundant in the conduction portion of the respiratory tract, (ii) ACE2 mRNA occurs at a lower abundance compared to TMPRSS2 mRNA, (iii) co-expression of ACE2-TMPRSS2 mRNAs is highest in those species with the highest susceptibility to SARS-CoV-2 infection (i.e., cats, Syrian hamsters, and white-tailed deer), and (iv) expression of ACE2 and TMPRSS2 mRNA was not altered following SARS-CoV-2 infection. Our results demonstrate that while specific regions of the respiratory tract are enriched in ACE2 and TMPRSS2 mRNAs in different animal species, this is only a partial determinant of susceptibility to SARS-CoV-2 infection.IMPORTANCESARS-CoV-2 infects a wide array of domestic and wild animals, raising concerns regarding its evolutionary dynamics in animals and potential for spillback transmission of emerging variants to humans. Hence, SARS-CoV-2 infection in animals has significant public health relevance. Host factors determining animal susceptibility to SARS-CoV-2 are vastly unknown, and their characterization is critical to further understand susceptibility and viral dynamics in animal populations and anticipate potential spillback transmission. Here, we quantitatively assessed the distribution and abundance of the two most important host factors, angiotensin-converting enzyme 2 and transmembrane serine protease 2, in the respiratory tract of various animal species and humans. Our results demonstrate that while specific regions of the respiratory tract are enriched in these two host factors, they are only partial determinants of susceptibility. Detailed analysis of additional host factors is critical for our understanding of the underlying mechanisms governing viral susceptibility and reservoir hosts.

Emergence of SARS and COVID-19 and preparedness for the next emerging disease X

Severe acute respiratory syndrome (SARS) and Coronavirus disease 2019 (COVID-19) are two human Coronavirus diseases emerging in this century, posing tremendous threats to public health and causing great loss to lives and economy. In this review, we retrospect the studies tracing the molecular evolution of SARS-CoV, and we sort out current research findings about the potential ancestor of SARS-CoV-2. Updated knowledge about SARS-CoV-2-like viruses found in wildlife, the animal susceptibility to SARS-CoV-2, as well as the interspecies transmission risk of SARS-related coronaviruses (SARSr-CoVs) are gathered here. Finally, we discuss the strategies of how to be prepared against future outbreaks of emerging or re-emerging coronaviruses.

The role of receptors in the cross-species spread of coronaviruses infecting humans and pigs

The pandemic caused by SARS-CoV-2, which has proven capable of infecting over 30 animal species, highlights the critical need for understanding the mechanisms of cross-species transmission and the emergence of novel coronavirus strains. The recent discovery of CCoV-HuPn-2018, a recombinant alphacoronavirus from canines and felines that can infect humans, along with evidence of SARS-CoV-2 infection in pig cells, underscores the potential for coronaviruses to overcome species barriers. This review investigates the origins and cross-species transmission of both human and porcine coronaviruses, with a specific emphasis on the instrumental role receptors play in this process.

An overview of SARS-CoV2 natural infections in companion animals: A systematic review of the current evidence

This systematic review provides a comprehensive overview of natural SARS-CoV-2 infections in companion animals. The findings show that these infections are relatively rare. Among the examined dogs, only 1.32% tested positive for SARS-CoV-2, while for cats, the rate was 1.55%. Infections in rabbits and ferrets were even less common, at less than 1%. These results support previous research indicating the infrequency of natural infections in companion animals. The review also includes updated studies that involved various pets, such as cats, dogs, ferrets, and rabbits. The majority of the studies analyzed were primarily concerned with screening pets that visited veterinary clinics, regardless of whether they showed any specific signs of SARS-CoV-2 infection. Only a limited number of studies investigated infections in animals suspected of being in contact with owners or other animals that had COVID-19 or were exhibiting symptoms. The most common variant identified among the SARS-CoV-2 variants in the reviewed studies was B.1.1.7 (alpha), followed by B.1.617.2 (delta), B.1.526 (Iota), and others. The emergence of these variants raises concerns about their potential for increased transmissibility and virulence, highlighting the importance of ongoing monitoring of SARS-CoV-2 infections in both humans and animals. Furthermore, most of the reviewed studies indicated that infected pets either showed no symptoms or experienced mild symptoms. This aligns with previous reports suggesting that animals infected with SARS-CoV-2 generally have less severe illness compared to humans. However, it is essential to recognize the possibility of severe illness or death in animals, particularly those with underlying health conditions. Continuous surveillance of SARS-CoV-2 infections in companion animals is crucial for better understanding the virus's epidemiology in animals and developing effective strategies to protect both animal and human health.

SARS-CoV-2 seroprevalence determination in pets and camels in Egypt using multispecies enzyme-linked immunosorbent assay

The coronavirus disease 2019 (COVID-19) pandemic has translated into a worldwide economic recession and public health crisis. Bats have been incriminated as the main natural host for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the causative agent of the COVID-19 pandemic. However, the reservoir and carrier hosts of the virus remain unknown. Therefore, a cross sectional serosurvey study was performed to estimate antibodies to SARS-CoV-2. To assess IgM antibodies to SARS-CoV-2 nucleocapsid protein (NP), a SARS-CoV-2 Double Antigen Multispecies diagnostic enzyme-linked immunosorbent assay kit was used. The seropositive samples were confirmed and validated by measuring IgG antibody titers in sera. The enrolled animals were from different locations in the Giza governorate, Egypt, and were sampled at the time of the pandemic; they comprised 92 companion animals and 92 domestic camels. The study established that 4.76% (1/21 clinical samples) of dogs, 7.69% of cats (1/13 shelter samples) and 1.08% (1/92) of camels, had measurable SARS-CoV-2 NP IgM antibodies. All IgM-seropositive samples were IgG positive with a measurable titer of 34.5, 28.6, and 25.8 UI/mL for dog, cat, and camels, respectively. According to our best knowledge, this study was the first to assess SARS-CoV-2 seroprevalence in the specific animals investigated in Egypt. These results may herald a promising epidemiological role for pet animals and camels in SARS-CoV-2 virus maintenance. Thus, our study's results ought to be confirmed with a nationwide seroprevalence study, and further studies are required to clarify whether these animals act as active or passive carriers.

Suburban Population of Bobcats (Lynx rufus) in Connecticut, USA, Tested Negative for SARS-CoV-2, November 2021-February 2022

A SARS-CoV-2 genomic and serologic survey was performed in a population of bobcats (Lynx rufus) inhabiting the state of Connecticut, USA. Wild animal populations are becoming established in densely populated cities with increased likelihood of direct or indirect contact with humans, as well as with household cats and dogs. Wild-caught bobcats (n=38) tested negative for SARS-CoV-2 genomic RNA by reverse-transcription quantitative PCR and for virus-neutralizing antibodies by ELISA, suggesting that either the species is not susceptible to SARS-CoV-2 or that the surveyed population has not yet been exposed to a source of infectious virus. However, this limited survey cannot rule out that human-to-bobcat or unknown reservoir-to-bobcat transmission of the virus occurs in nature.

Evidence of SARS-CoV-2 infection and co-infections in stray cats in Brazil

The zoonotic virus SARS-CoV-2, which causes severe acute respiratory syndrome in humans (COVID-19), has been identified in cats. Notably, most positive cases were in cats that had close contact with infected humans, suggesting a role for humans in animal transmission routes. Previous studies have suggested that animals with immune depletion are more susceptible to SARS-CoV-2 infection. To date, there is limited evidence of SARS-CoV-2 infections in stray and free-range cats affected by other pathogens. In this study, we investigated infections caused by SARS-CoV-2, Leishmania spp., Toxoplasma gondii, Mycoplasma spp., Bartonella spp., Feline leukemia virus (FeLV), and Feline immunodeficiency virus (FIV) in stray cats from an urban park in Brazil during the COVID-19 pandemic. From February to September 2021, 78 mixed-breed cats were tested for SARS-CoV-2 and hemopathogens using molecular analysis at Américo Renné Giannetti Municipal Park, Belo Horizonte, Minas Gerais, Brazil. An enzyme-linked immunosorbent assay (ELISA) was used to detect IgG in T. gondii. None of the animals in this study showed any clinical signs of infections. The SARS-CoV-2 virus RNA was detected in 7.7 % of cats, and a whole virus genome sequence analysis revealed the SARS-CoV-2 Delta lineage (B.1.617.2). Phylogenetic analysis showed that SARS-CoV-2 isolated from cats was grouped into the sublineage AY.99.2, which matches the epidemiological scenario of COVID-19 in the urban area of our study. Leishmania infantum was detected and sequenced in 9 % of cats. The seroprevalence of T. gondii was 23.1 %. Hemotropic Mycoplasma spp. was detected in 7.7 % of the cats, with Mycoplasma haemofelis and Candidatus Mycoplasma haemominutum being the most common. Bartonella henselae and Bartonella clarridgeiae were detected in 38.5 % of the cats, FeLV was detected in 17,9 %, and none of the cats studied tested positive for FIV. This study reports, for the first time, the SARS-CoV-2 infection with whole-genome sequencing in stray cats in southeastern Brazil and co-infection with other pathogens, including Bartonella spp. and Feline leukemia virus. Our study observed no correlation between SARS-CoV-2 and the other detected pathogens. Our results emphasize the importance of monitoring SARS-CoV-2 in stray cats to characterize their epidemiological role in SARS-CoV-2 infection and reinforce the importance of zoonotic disease surveillance.

The risk of pet animals in spreading severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and public health importance: An updated review

Since the outbreak of SARS-CoV-2 was first identified in 2019, it has been reported that the virus could infect a variety of animals either naturally or experimentally. This review discusses the occurrence SARS-CoV-2 in dogs and cats and the role of these animals in transmitting coronavirus disease 2019 (COVID-19) to their owners. The data were collected from epidemiological studies and case reports that focused on studying the occurrence of SARS-CoV-2 in pet animals and their owners. Epidemiological studies and case reports indicate that dogs and cats are infected with SARS-CoV-2 either naturally or experimentally; however, the global number of naturally infected animals is far lower than the number of people who have COVID-19. These studies demonstrate that pet animals acquire the infection from direct contact with COVID-19-infected owners. Currently, there are no studies reporting that dogs and cats can transmit SARS-CoV-2 to other animals and humans, under natural conditions. The emergence of SARS-CoV-2 infection in companion animals (dogs and cats) in different countries worldwide raises concerns that pets are at higher risk for spreading and transmitting SARS-CoV-2 to humans and other animals, which poses a hazard to the public health. Therefore, investigating the role of dogs and cats in the transmission and epidemiology of SARS-CoV-2 will help us to design and implement appropriate preventive measures against the further transmission of SARS-CoV-2.

Preliminary Study on the Efficacy of a Recombinant, Subunit SARS-CoV-2 Animal Vaccine against Virulent SARS-CoV-2 Challenge in Cats

The objective of this work was to evaluate the safety and efficacy of a recombinant, subunit SARS-CoV-2 animal vaccine in cats against virulent SARS-CoV-2 challenge. Two groups of cats were immunized with two doses of either a recombinant SARS-CoV-2 spike protein vaccine or a placebo, administered three weeks apart. Seven weeks after the second vaccination, both groups of cats were challenged with SARS-CoV-2 via the intranasal and oral routes simultaneously. Animals were monitored for 14 days post-infection for clinical signs and viral shedding before being humanely euthanized and evaluated for macroscopic and microscopic lesions. The recombinant SARS-CoV-2 spike protein subunit vaccine induced strong serologic responses post-vaccination and significantly increased neutralizing antibody responses post-challenge. A significant difference in nasal and oral viral shedding, with significantly reduced virus load (detected using RT-qPCR) was observed in vaccinates compared to mock-vaccinated controls. Duration of nasal, oral, and rectal viral shedding was also significantly reduced in vaccinates compared to controls. No differences in histopathological lesion scores were noted between the two groups. Our findings support the safety and efficacy of the recombinant spike protein-based SARS-CoV-2 vaccine which induced high levels of neutralizing antibodies and reduced nasal, oral, and rectal viral shedding, indicating that this vaccine will be efficacious as a COVID-19 vaccine for domestic cats.

Seroprevalence of SARS-CoV-2 antibodies in dogs and cats during the early and mid-pandemic periods in Japan

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has continued to circulate in humans since its emergence in 2019. While infection in humans continues, numerous spillover events to at least 32 animal species, including companion and zoo animals, have been reported. Since dogs and cats are highly susceptible to SARS-CoV-2 and have direct contact with their owners and other household members, it is important to know the prevalence of SARS-CoV-2 in dogs and cats. Here, we established an ELISA to detect serum antibodies against the receptor-binding domain and the ectodomain of the SARS-CoV-2 spike and nucleocapsid proteins. Using this ELISA, we assessed seroprevalence in 488 dog serum samples and 355 cat serum samples that were collected during the early pandemic period (between May and June of 2020) and 312 dog serum samples and 251 cat serum samples that were collected during the mid-pandemic period (between October 2021 and January 2022). We found that two dog serum samples (0.41%) collected in 2020, one cat serum sample (0.28%) collected in 2020, and four cat serum samples (1.6%) collected in 2021 were positive for antibodies against SARS-CoV-2. No dog serum samples collected in 2021 were positive for these antibodies. We conclude that the seroprevalence of SARS-CoV-2 antibodies in dogs and cats in Japan is low, suggesting that these animals are not a major SARS-CoV-2 reservoir.

Neurologic Effects of SARS-CoV-2 Transmitted among Dogs

SARS-CoV-2 induces illness and death in humans by causing systemic infections. Evidence suggests that SARS-CoV-2 can induce brain pathology in humans and other hosts. In this study, we used a canine transmission model to examine histopathologic changes in the brains of dogs infected with SARS-CoV-2. We observed substantial brain pathology in SARS-CoV-2-infected dogs, particularly involving blood-brain barrier damage resembling small vessel disease, including changes in tight junction proteins, reduced laminin levels, and decreased pericyte coverage. Furthermore, we detected phosphorylated tau, a marker of neurodegenerative disease, indicating a potential link between SARS-CoV-2-associated small vessel disease and neurodegeneration. Our findings of degenerative changes in the dog brain during SARS-CoV-2 infection emphasize the potential for transmission to other hosts and induction of similar signs and symptoms. The dynamic brain changes in dogs highlight that even asymptomatic individuals infected with SARS-CoV-2 may develop neuropathologic changes in the brain.

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.

Infection Dynamics, Pathogenesis, and Immunity to SARS-CoV-2 in Naturally Susceptible Animal Species

SARS-CoV-2, the causative agent of the COVID-19 pandemic, presents a broad host range. Domestic cats and white-tailed deer (WTD) are particularly susceptible to SARS-CoV-2 with multiple variant strains being associated with infections in these species. The virus replicates in the upper respiratory tract and in associated lymphoid tissues, and it is shed through oral and nasal secretions, which leads to efficient transmission of the virus to contact animals. Robust cell-mediated and humoral immune responses are induced upon infection in domestic cats, which curb the progression of clinical disease and are associated with control of infection. In WTD, high levels of neutralizing Abs are detected early upon infection. In this review, the current understanding of the infection dynamics, pathogenesis, and immune responses to SARS-CoV-2 infection in animals, with special focus on naturally susceptible felids and WTD, are discussed.

A retrospective study of SARS-CoV-2 seroprevalence in dogs and cats in the Community of Madrid, Spain

To date, susceptibility to SARS-CoV-2 infection in domestic animals including cats and dogs has been described. However, it is important to carry out passive surveillance of these animals to be aware of any changes in the outcomes of the disease in these species that may occur. In this study, we have performed a retrospective study in which we analyzed sera (n = 1,640) from random animals: dogs (n = 1,381) and cats (n = 259) belonging to both homes (n = 1,533) and animal protection centers (n = 107) in the Community of Madrid, Spain. Neutralizing antibodies were evaluated between November 2021 and May 2022 using a surrogate ELISA kit to determine the seroprevalence. Based on the results obtained, a few animals (both cats and dogs) presented neutralizing antibodies to SARS-CoV-2 (2.3%), all of them from private owners. However, the seroprevalence in cats (4.6%) resulted to be almost twice as much as in dogs (1.9%) which reinforces that cats' susceptibility to the infection seems higher than in the case of dogs, maybe due to the lower ACE2 expression of the dogs in the respiratory tract. These findings also confirm that the probability of infection is considerably higher in domestic animals in close contact with infected owners, compared to animals living in animal shelters whose contact with humans is markedly lower.

SARS-CoV-2 prevalence in domestic and wildlife animals: A genomic and docking based structural comprehensive review

The SARS-CoV-2 virus has been identified as the infectious agent that led to the COVID-19 pandemic, which the world has seen very recently. Researchers have linked the SARS-CoV-2 outbreak to bats for the zoonotic spread of the virus to humans. Coronaviruses have a crown-like shape and positive-sense RNA nucleic acid. It attaches its spike glycoprotein to the host angiotensin-converting enzyme 2 (ACE2) receptor. Coronavirus genome comprises 14 ORFs and 27 proteins, spike glycoprotein being one of the most critical proteins for viral pathogenesis. Many mammals and reptiles, including bats, pangolins, ferrets, snakes, and turtles, serve as the principal reservoirs for this virus. But many experimental investigations have shown that certain domestic animals, including pigs, chickens, dogs, cats, and others, may also be able to harbor this virus, whether they exhibit any symptoms. These animals act as reservoirs for SARS-CoV, facilitating its zoonotic cross-species transmission to other species, including humans. In this review, we performed a phylogenetic analysis with multiple sequence alignment and pairwise evolutionary distance analysis, which revealed the similarity of ACE2 receptors in humans, chimpanzees, domestic rabbits, house mice, and golden hamsters. Pairwise RMSD analysis of the spike protein from some commonly reported SARS-CoV revealed that bat and pangolin coronavirus shared the highest structural similarity with human coronavirus. In a further experiment, molecular docking confirmed a higher affinity of pig, bat, and pangolin coronavirus spike proteins' affinity to the human ACE2 receptor. Such comprehensive structural and genomic analysis can help us to forecast the next likely animal source of these coronaviruses that may infect humans. To combat these zoonotic illnesses, we need a one health strategy that considers the well-being of people and animals and the local ecosystem.

Current state-of-the-art and potential future therapeutic drugs against COVID-19

The novel coronavirus disease (COVID-19) continues to endanger human health, and its therapeutic drugs are under intensive research and development. Identifying the efficacy and toxicity of drugs in animal models is helpful for further screening of effective medications, which is also a prerequisite for drugs to enter clinical trials. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) invades host cells mainly by the S protein on its surface. After the SARS-CoV-2 RNA genome is injected into the cells, M protein will help assemble and release new viruses. RdRp is crucial for virus replication, assembly, and release of new virus particles. This review analyzes and discusses 26 anti-SARS-CoV-2 drugs based on their mechanism of action, effectiveness and safety in different animal models. We propose five drugs to be the most promising to enter the next stage of clinical trial research, thus providing a reference for future drug development.

SARS-CoV-2 in Domestic UK Cats from Alpha to Omicron: Swab Surveillance and Case Reports

Although domestic cats are susceptible to infection with SARS-CoV-2, the role of the virus in causing feline disease is less well defined. We conducted a large-scale study to identify SARS-CoV-2 infections in UK pet cats, using active and passive surveillance. Remnant feline respiratory swab samples, submitted for other pathogen testing between May 2021 and February 2023, were screened using RT-qPCR. In addition, we appealed to veterinarians for swab samples from cats suspected of having clinical SARS-CoV-2 infections. Bespoke testing for SARS-CoV-2 neutralising antibodies was also performed, on request, in suspected cases. One RT-qPCR-positive cat was identified by active surveillance (1/549, 0.18%), during the Delta wave (1/175, 0.57%). Passive surveillance detected one cat infected with the Alpha variant, and two of ten cats tested RT-qPCR-positive during the Delta wave. No cats tested RT-qPCR-positive after the emergence of Omicron BA.1 and its descendants although 374 were tested by active and eleven by passive surveillance. We describe four cases of SARS-CoV-2 infection in pet cats, identified by RT-qPCR and/or serology, that presented with a range of clinical signs, as well as their SARS-CoV-2 genome sequences. These cases demonstrate that, although uncommon in cats, a variety of clinical signs can occur.

Lack of SARS-CoV-2 Viral RNA Detection among a Convenience Sampling of Ohio Wildlife, Companion, and Agricultural Animals, 2020-2021

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in humans in late 2019 and spread rapidly, becoming a global pandemic. A zoonotic spillover event from animal to human was identified as the presumed origin. Subsequently, reports began emerging regarding spillback events resulting in SARS-CoV-2 infections in multiple animal species. These events highlighted critical links between animal and human health while also raising concerns about the development of new reservoir hosts and potential viral mutations that could alter the virulence and transmission or evade immune responses. Characterizing susceptibility, prevalence, and transmission between animal species became a priority to help protect animal and human health. In this study, we coalesced a large team of investigators and community partners to surveil for SARS-CoV-2 in domestic and free-ranging animals around Ohio between May 2020 and August 2021. We focused on species with known or predicted susceptibility to SARS-CoV-2 infection, highly congregated or medically compromised animals (e.g., shelters, barns, veterinary hospitals), and animals that had frequent contact with humans (e.g., pets, agricultural animals, zoo animals, or animals in wildlife hospitals). This included free-ranging deer (n = 76 individuals), free-ranging mink (n = 57), multiple species of bats (n = 59), and other wildlife in addition to domestic cats (n = 275) and pigs (n = 184). In total, we tested 792 individual animals (34 species) via rRT-PCR for SARS-CoV-2 RNA. SARS-CoV-2 viral RNA was not detected in any of the tested animals despite a major peak in human SARS-CoV-2 cases that occurred in Ohio subsequent to the peak of animal samplings. Importantly, we did not test for SARS-CoV-2 antibodies in this study, which limited our ability to assess exposure. While the results of this study were negative, the surveillance effort was critical and remains key to understanding, predicting, and preventing the re-emergence of SARS-CoV-2 in humans or animals.

Interspecies transmission of SARS CoV-2 with special emphasis on viral mutations and ACE-2 receptor homology roles

COVID-19 outbreak was first reported in 2019, Wuhan, China. The spillover of the disease caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), to a wide range of pet, zoo, wild, and farm animals has emphasized potential zoonotic and reverse zoonotic viral transmission. Furthermore, it has evoked inquiries about susceptibility of different animal species to SARS-CoV-2 infection and role of these animals as viral reservoirs. Therefore, studying susceptible and non-susceptible hosts for SARS-CoV-2 infection could give a better understanding for the virus and will help in preventing further outbreaks. Here, we review structural aspects of SARS-CoV-2 spike protein, the effect of the different mutations observed in the spike protein, and the impact of ACE2 receptor variations in different animal hosts on inter-species transmission. Moreover, the SARS-CoV-2 spillover chain was reviewed. Combination of SARS-CoV-2 high mutation rate and homology of cellular ACE2 receptors enable the virus to transcend species barriers and facilitate its transmission between humans and animals.

Molecular detection of SARS-CoV-2 in domestic cats in close contact with positively-infected owners in Tehran, Iran in 2021

Objectives

In 2019, COVID-19 emerged in China and has since spread worldwide. Owing to the virus's ability to adhere to specific receptors, cats are susceptible to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The popularity of pet cats in Iran has sparked fears of human-cat-human transmission of the virus. This study aimed to identify positive cases in cats owned by people infected with SARS-CoV-2, to determine if they remained positive for >3 weeks and to examine the virus genome isolated from a number of cats and one of their owners.

Methods

A total of 30 cats were sampled approximately 3 days after their owners tested positive (day 1), and 3 weeks later, in strict accordance with health regulations. Rectal and oropharyngeal samples were collected. All samples were subjected to a qualitative PCR and reverse transcription PCR. The S-gene region was partially sequenced in positive samples and the results were used to create a phylogenetic tree.

Results

SARS-CoV-2 was detected in 7/30 (23.3%) cats examined. In the third week, every cat tested negative. The sequence data of positive cats and one of their owners revealed that the retrieved RNAs belonged to the alpha variation. The genetic distance between the samples and the reference sequence (20I/B.1.1.7: OM003849, MZ344997) was minimal, with a 99% similarity. Positive samples of cats had four mutations in gene S. Amino acid substitutions in the spike glycoprotein at positions N501Y, A570D, D614G and P681H were recorded in the isolates compared with 780 other sequences of Iranian strains.

Conclusions and relevance

This study confirmed the presence of SARS-CoV-2-infected cats living in close contact with infected owners. Despite cats' susceptibility to COVID-19, the risk of severe infection in these animals is low, as evidenced by the lack of clinical signs in positive cats.

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.

Efficient Direct and Limited Environmental Transmission of SARS-CoV-2 Lineage B.1.22 in Domestic Cats

The susceptibility of domestic cats to infection with SARS-CoV-2 has been demonstrated by several experimental studies and field observations. We performed an extensive study to further characterize the transmission of SARS-CoV-2 between cats, through both direct and indirect contact. To that end, we estimated the transmission rate parameter and the decay parameter for infectivity in the environment. Using four groups of pair-transmission experiment, all donor (inoculated) cats became infected, shed virus, and seroconverted, while three out of four direct contact cats got infected, shed virus, and two of those seroconverted. One out of eight cats exposed to a SARS-CoV-2-contaminated environment became infected but did not seroconvert. Statistical analysis of the transmission data gives a reproduction number R0 of 2.18 (95% CI = 0.92 to 4.08), a transmission rate parameter β of 0.23 day-1 (95% CI = 0.06 to 0.54), and a virus decay rate parameter μ of 2.73 day-1 (95% CI = 0.77 to 15.82). These data indicate that transmission between cats is efficient and can be sustained (R0 > 1), however, the infectiousness of a contaminated environment decays rapidly (mean duration of infectiousness 1/2.73 days). Despite this, infections of cats via exposure to a SARS-CoV-2-contaminated environment cannot be discounted if cats are exposed shortly after contamination. IMPORTANCE This article provides additional insight into the risk of infection that could arise from cats infected with SARS-CoV-2 by using epidemiological models to determine transmission parameters. Considering that transmission parameters are not always provided in the literature describing transmission experiments in animals, we demonstrate that mathematical analysis of experimental data is crucial to estimate the likelihood of transmission. This article is also relevant to animal health professionals and authorities involved in risk assessments for zoonotic spill-overs of SARS-CoV-2. Last but not least, the mathematical models to calculate transmission parameters are applicable to analyze the experimental transmission of other pathogens between animals.

Baculovirus-expressed self-assembling SARS-CoV-2 nanoparticle vaccines targeting the S protein induce protective immunity in mice

Spike (S) protein, a homotrimeric glycoprotein, is the most important antigen target for SARS-CoV-2 vaccines. A complete simulation of the advanced structure of this homotrimer during subunit vaccine development is the most likely method to improve its immunoprotective effects. In this study, preparation strategies for the S protein receptor-binding domain, S1 region, and ectodomain trimer nanoparticles were designed using ferritin nanoparticle self-assembly technology. The Bombyx mori baculovirus expression system was used to prepare three nanoparticle vaccines with high expression levels recorded in silkworms. The results in mice showed that the nanoparticle vaccine prepared using this strategy could induce immune responses when administered via both the subcutaneous administration and oral routes. Given the stability of these ferritin-based nanoparticle vaccines, an easy-to-use and low-cost oral immunization strategy can be employed in vaccine blind areas attributed to shortages of ultralow-temperature equipment and medical resources in underdeveloped areas. Oral vaccines are also promising candidates for limiting the spread of SARS-CoV-2 in domestic and farmed animals, especially in stray and wild animals.

SARS-CoV-2 Surveillance between 2020 and 2021 of All Mammalian Species in Two Flemish Zoos (Antwerp Zoo and Planckendael Zoo)

The COVID-19 pandemic has led to millions of human infections and deaths worldwide. Several other mammal species are also susceptible to SARS-CoV-2, and multiple instances of transmission from humans to pets, farmed mink, wildlife and zoo animals have been recorded. We conducted a systematic surveillance of SARS-CoV-2 in all mammal species in two zoos in Belgium between September and December 2020 and July 2021, in four sessions, and a targeted surveillance of selected mammal enclosures following SARS-CoV-2 infection in hippopotamuses in December 2021. A total of 1523 faecal samples from 103 mammal species were tested for SARS-CoV-2 via real-time PCR. None of the samples tested positive for SARS-CoV-2. Additional surrogate virus neutralisation tests conducted on 50 routinely collected serum samples from 26 mammal species were all negative. This study is the first to our knowledge to conduct active SARS-CoV-2 surveillance for several months in all mammal species of a zoo. We conclude that at the time of our investigation, none of the screened animals were excreting SARS-CoV-2.

Immune Responses and Pathogenesis following Experimental SARS-CoV-2 Infection in Domestic Cats

Several reports demonstrated the susceptibility of domestic cats to SARS-CoV-2 infection. Here, we describe a thorough investigation of the immune responses in cats after experimental SARS-CoV-2 inoculation, along with the characterization of infection kinetics and pathological lesions. Specific pathogen-free domestic cats (n = 12) were intranasally inoculated with SARS-CoV-2 and subsequently sacrificed on DPI (days post-inoculation) 2, 4, 7 and 14. None of the infected cats developed clinical signs. Only mild histopathologic lung changes associated with virus antigen expression were observed mainly on DPI 4 and 7. Viral RNA was present until DPI 7, predominantly in nasal and throat swabs. The infectious virus could be isolated from the nose, trachea and lungs until DPI 7. In the swab samples, no biologically relevant SARS-CoV-2 mutations were observed over time. From DPI 7 onwards, all cats developed a humoral immune response. The cellular immune responses were limited to DPI 7. Cats showed an increase in CD8+ cells, and the subsequent RNA sequence analysis of CD4+ and CD8+ subsets revealed a prominent upregulation of antiviral and inflammatory genes on DPI 2. In conclusion, infected domestic cats developed a strong antiviral response and cleared the virus within the first week after infection without overt clinical signs and relevant virus mutations.

High seroprevalence of SARS-CoV-2 antibodies in household cats and dogs of Lebanon

The COVID-19 pandemic has been declared in late 2019. It is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Flu-like symptoms and acute respiratory illnesses are the main manifestations of the disease. Recent studies have confirmed the susceptibility of domestic animals to SARS-CoV-2 infection. However, the seroprevalence of SARS-CoV-2 in household pets and the importance of pets in the epidemiology of this infection remain unknown. In Lebanon, there is no epidemiological data regarding SARS-CoV-2 infection in companion animals. Thus, this investigation aimed to determine the seroprevalence of SARS-CoV-2 antibodies in household pets of Lebanon during the COVID-19 pandemic. A cross-sectional study was carried out between April 2020 and February 2021. Blood samples from 145 cats and 180 dogs were collected from 12 veterinary clinics located in the North, Mount, and Beirut governorates. A validated ELISA assay was used to detect the anti- SARS-CoV-2 in the sera of the tested animals. An overall seroprevalence of 16.92% (55/325) was reported; 13.79% seroprevalence was found in cats (20/145) and 19.44% (35/180) in dogs. The young age and the cold season were significantly associated with an increased seropositivity rate to SARS-CoV-2 infection (P < 0.01). These results confirm the circulation of SARS-CoV-2 in household pets, in various geographical regions in Lebanon. Although, there is a lack of evidence to suggest that naturally infected pets could transmit the SARS-CoV-2 infection. Yet, owners diagnosed with COVID-19 should limit their contact with their animals during the course of the disease to curb the risk of transmission.

Do pathogens always evolve to be less virulent? The virulence–transmission trade-off in light of the COVID-19 pandemic

The direction the evolution of virulence takes in connection with any pathogen is a long-standing question. Formerly, it was theorized that pathogens should always evolve to be less virulent. As observations were not in line with this theoretical outcome, new theories emerged, chief among them the transmission–virulence trade-off hypotheses, which predicts an intermediate level of virulence as the endpoint of evolution. At the moment, we are very much interested in the future evolution of COVID-19’s virulence. Here, we show that the disease does not fulfill all the assumptions of the hypothesis. In the case of COVID-19, a higher viral load does not mean a higher risk of death; immunity is not long-lasting; other hosts can act as reservoirs for the virus; and death as a consequence of viral infection does not shorten the infectious period. Consequently, we cannot predict the short- or long-term evolution of the virulence of COVID-19.

SARS-CoV-2 Infection and Clinical Signs in Cats and Dogs from Confirmed Positive Households in Germany

On a global scale, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses a serious threat to the health of the human population. Not only humans can be infected, but also their companion animals. The antibody status of 115 cats and 170 dogs, originating from 177 German households known to have been SARS-CoV-2 positive, was determined by enzyme-linked immunosorbent assay (ELISA), and the results were combined with information gathered from a questionnaire that was completed by the owner(s) of the animals. The true seroprevalences of SARS-CoV-2 among cats and dogs were 42.5% (95% CI 33.5–51.9) and 56.8% (95% CI 49.1–64.4), respectively. In a multivariable logistic regression accounting for data clustered in households, for cats, the number of infected humans in the household and an above-average contact intensity turned out to be significant risk factors; contact with humans outside the household was a protective factor. For dogs, on the contrary, contact outside the household was a risk factor, and reduced contact, once the human infection was known, was a significant protective factor. No significant association was found between reported clinical signs in animals and their antibody status, and no spatial clustering of positive test results was identified.

Cross-species transmission of coronaviruses with a focus on severe acute respiratory syndrome coronavirus 2 infection in animals: a review for the veterinary practitioner

AbstractIn 2019 a novel coronavirus termed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged from an unidentified source and spread rapidly among humans worldwide. While many human infections are mild, some result in severe clinical disease that in a small proportion of infected people is fatal. The pandemic spread of SARS-CoV-2 has been facilitated by efficient human-to-human transmission of the virus, with no data to indicate that animals contributed to this global health crisis. However, a range of domesticated and wild animals are also susceptible to SARS-CoV-2 infection under both experimental and natural conditions. Humans are presumed to be the source of most animal infections thus far, although natural transmission between mink and between free-ranging deer has occurred, and occasional natural transmission between cats cannot be fully excluded. Considering the ongoing circulation of the virus among people, together with its capacity to evolve through mutation and recombination, the risk of the emergence of animal-adapted variants is not negligible. If such variants remain infectious to humans, this could lead to the establishment of an animal reservoir for the virus, which would complicate control efforts. As such, minimising human-to-animal transmission of SARS-CoV-2 should be considered as part of infection control efforts. The aim of this review is to summarise what is currently known about the species specificity of animal coronaviruses, with an emphasis on SARS-CoV-2, in the broader context of factors that facilitate cross-species transmission of viruses.

Stability of SARS-CoV-2 in Biological Fluids of Animals

Since its first emergence in 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has continued to evolve genetically, jump species barriers, and expand its host range. There is growing evidence of interspecies transmission including infection of domestic animals and widespread circulation in wildlife. However, knowledge of SARS-CoV-2 stability in animal biological fluids and their role in transmission is still limited as previous studies focused on human biological fluids. Therefore, this study aimed to determine the SARS-CoV-2 stability in biological fluids from three animal species, cats, sheep and white-tailed deer (WTD). Saliva, feces, 10% fecal suspensions, and urine of cats, sheep, and WTD were mixed with a known concentration of virus and incubated under indoor and three different climatic conditions. Our results show that the virus was stable for up to 1 day in the saliva of cats, sheep, and WTD regardless of the environmental conditions. The virus remained infectious for up to 6 days in feces and 15 days in fecal suspension of WTD, whereas the virus was rather unstable in cat and sheep feces and fecal suspensions. We found the longest survival of SARS-CoV-2 in the urine of cats, sheep, and WTD. Furthermore, side-by-side comparison with different SARS-CoV-2 strains showed that the Alpha, Delta, and Omicron variants of concern were less stable than the ancestral Wuhan-like strain in WTD fecal suspension. The results of our study provide valuable information for assessing the potential role of various animal biological fluids in SARS-CoV-2 transmission.

Extracellular Vesicle-Based SARS-CoV-2 Vaccine

Messenger ribonucleic acid (RNA) vaccines are mainly used as SARS-CoV-2 vaccines. Despite several issues concerning storage, stability, effective period, and side effects, viral vector vaccines are widely used for the prevention and treatment of various diseases. Recently, viral vector-encapsulated extracellular vesicles (EVs) have been suggested as useful tools, owing to their safety and ability to escape from neutral antibodies. Herein, we summarize the possible cellular mechanisms underlying EV-based SARS-CoV-2 vaccines.

Severe acute respiratory syndrome coronavirus-2 detection in domestic animals as a reservoir for the virus transmission to humans in Yogyakarta, Indonesia

Background and Aim: The coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) that attacks the respiratory and digestive tract. The SARS-CoV-2 showed systemic characteristics with various clinical symptoms from subclinical to fatal (causing death). Transmission of SARS-CoV-2 has been reported to occur from humans to pets (cats, dogs, tigers, ferrets, and poultry). Knowledge about the role of domestic animals in the transmission of SARS-CoV-2 to humans, and as reservoirs of this virus needs to be investigated further. This study aimed to detect the presence of SARS-CoV-2 in domestic animals such as dogs, cats, pigs, cows, birds, and bats that are often in contact with humans. Materials and Methods: A total of 157 samples, which included nasopharyngeal and oropharyngeal swabs, along with sera samples from domestic animals such as cats, pigs, cows, birds, and bats, were taken from Veterinary Hospitals, Veterinary Clinics, and farms around the Yogyakarta region. Detection of the virus was done using rapid detection of viral antigens, antibodies, and reverse transcriptase-polymerase chain reaction (RT-PCR) technique. Results: The results showed that 5/157 (3.1%) samples found positive against the COVID-19 virus using a rapid antibody test; however, the results were negative on the rapid antigen and RT-PCR tests. Antibody-positive samples came from animals that had a history of household COVID-19 human infection. Conclusion: Thus, findings of the present study conclude that there is a potential for transmission of the COVID-19 virus between animals and humans.

SARS-CoV-2 Affects Both Humans and Animals: What Is the Potential Transmission Risk? A Literature Review

In March 2020, the World Health Organization Department declared the coronavirus (COVID-19) outbreak a global pandemic, as a consequence of its rapid spread on all continents. The COVID-19 pandemic has been not only a health emergency but also a serious general problem as fear of contagion and severe restrictions put economic and social activity on hold in many countries. Considering the close link between human and animal health, COVID-19 might infect wild and companion animals, and spawn dangerous viral mutants that could jump back and pose an ulterior threat to us. The purpose of this review is to provide an overview of the pandemic, with a particular focus on the clinical manifestations in humans and animals, the different diagnosis methods, the potential transmission risks, and their potential direct impact on the human-animal relationship.

Host traits, ownership behaviour and risk factors of SARS-CoV-2 infection in domestic pets in Mexico

SARS-CoV-2 can infect pets under natural conditions, which raises questions about the risk factors related to the susceptibility of these animals to infection. The status of pet infection by SARS-CoV-2 in Mexico is not well-understood. We aimed to estimate the frequency of positive household cats and dogs to viral RNA and antibodies for SARS-CoV-2 during the second wave of human infections in Mexico, and to recognize the major risk factors related to host and pet ownership behaviour. We evaluated two study groups, cats and dogs from COVID-19-infected/-suspected households (n = 44) and those admitted for veterinary care for any reason at several veterinary hospitals in Puebla City, Mexico (n = 91). Using RT-PCR, we identified the presence of SARS-CoV-2 RNA in swabs of four dogs (18.18%) and zero cats in COVID-19-infected/-suspected households; within this group, 31.82% of dogs and 27.27% of cats were tested IgG ELISA-positive; and neutralizing antibodies were detected in one dog (4.55%) and two cats (9.09%). In the random group (pets evaluated at private clinics and veterinary teaching hospital), 25.00% of dogs and 43.59% of cats were ELISA-positive and only one cat showed neutralizing antibodies (2.56%). Older than 4-year-old, other pets at home, and daily cleaning of pet dish, were each associated with an increase in SARS-CoV-2 infection (p < 0.05). Allowing face lick, sharing bed/food with pets and owner tested positive or suspected COVID-19 were not significant risk factors, but more than 4 h the owner spent away from home during the lockdown for COVID-19 (OR = 0.37, p = 0.01), and outdoor pet food tray (OR = 0.32, p = 0.01) significantly decreased the risks of SARS-CoV-2 infection in pets, suggesting that time the owner spends with their pet is an important risk factor.

When COVID-19 sits on people's laps: A systematic review of SARS-CoV-2 infection prevalence in household dogs and cats

During the COVID-19 pandemic, questions were raised about whether SARS-CoV-2 can infect pets and the potential risks posed to and by their human owners. We performed a systematic review of studies on SARS-CoV-2 infection prevalence in naturally infected household dogs and cats conducted worldwide and published before January 2022. Data on SARS-CoV-2 infection prevalence, as determined by either molecular or serological methods, and accompanying information, were summarized. Screening studies targeting the general dog or cat populations were differentiated from those targeting households with known COVID-19-positive people. Studies focusing on stray, sheltered or working animals were excluded. In total, 17 studies were included in this review. Fourteen studies investigated cats, 13 investigated dogs, and 10 investigated both. Five studies reported molecular prevalence, 16 reported seroprevalence, and four reported both. All but two studies started and ended in 2020. Studies were conducted in eight European countries (Italy, France, Spain, Croatia, Germany, the Netherlands, UK, Poland), three Asian countries (Iran, Japan, China) and the USA. Both molecular and serological prevalence in the general pet population were usually below 5%, but exceeded 10% when COVID-19 positive people were known to be present in the household. A meta-analysis provided pooled seroprevalence estimates in the general pet population: 2.75% (95% Confidence Interval [CI]: 1.56-4.79%) and 0.82% (95% CI: 0.26-2.54%) for cats and dogs, respectively. This review highlighted the need for a better understanding of the possible epizootic implications of the COVID-19 pandemic, as well as the need for global standards for SARS-CoV-2 detection in pets.

Interactions between Humans and Dogs during the COVID-19 Pandemic: Recent Updates and Future Perspectives

COVID-19 is one of the deadliest epidemics. This pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but the role of dogs in spreading the disease in human society is poorly understood. This review sheds light on the limited susceptibility of dogs to COVID-19 infections which is likely attributed to the relatively low levels of angiotensin-converting enzyme 2 (ACE2) in the respiratory tract and the phylogenetic distance of ACE2 in dogs from the human ACE2 receptor. The low levels of ACE2 affect the binding affinity between spike and ACE2 proteins resulting in it being uncommon for dogs to spread the disease. To demonstrate the role of dogs in spreading COVID-19, we reviewed the epidemiological studies and prevalence of SARS-CoV-2 in dogs. Additionally, we discussed the use of detection dogs as a rapid and reliable method for effectively discriminating between SARS-CoV-2 infected and non-infected individuals using different types of samples (secretions, saliva, and sweat). We considered the available information on COVID-19 in the human-dog interfaces involving the possibility of transmission of COVID-19 to dogs by infected individuals and vice versa, the human-dog behavior changes, and the importance of preventive measures because the risk of transmission by domestic dogs remains a concern.

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.