The Emergence of SARS-CoV-2 within the Dog Population in Croatia: Host Factors and Clinical Outcome

A Large-Scale Serological Survey in Pets From October 2020 Through June 2021 in France Shows Significantly Higher Exposure to SARS-CoV-2 in Cats Compared to Dogs

INTRODUCTION

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has the potential to infect various animals, including domestic pets like dogs and cats. Many studies have documented infection in companion animals by molecular and serological methods. However, only a few have compared seroprevalence in cats and dogs from the general population, and these studies were limited by small sample sizes and collections over short periods. Our aim was to obtain a more accurate evaluation of seroprevalence in companion animals in France and to determine whether cats and dogs differ in their exposure to SARS-CoV-2.

METHODS

We conducted an extensive serological survey of SARS-CoV-2, collecting blood samples from 2036 cats and 3577 dogs during routine veterinary medical examinations across different regions of metropolitan France from October 2020 to June 2021. This period encompassed the peaks and onset of two waves, as well as the emergence of the first variants. A microsphere immunoassay targeting the receptor-binding domain and trimeric spike protein was used to detect anti-SARS-CoV-2 antibodies. A subset of 308 seropositive samples was tested for the presence of neutralising antibodies.

RESULTS

We determined an overall seroprevalence of anti-SARS-CoV-2 antibodies of 7.1% (95% confidence interval [CI]: 6.4%-7.8%) among the sampled pets. Cats exhibited a significantly higher seroprevalence (9.3%; 95% CI: 8.1%-10.1%) compared to dogs (5.9%; 95% CI: 5.2%-6.8%). Among the subset of seropositive samples, 81 (26.3%; 95% CI: 21.5%-31.6%) displayed neutralizing antibodies. Furthermore, seroprevalence in both species was lower in older animals and was not associated with sex. Finally, unlike cats, seroprevalence in dogs was found to be correlated with the date of sampling.

CONCLUSIONS

The large sample size enhances the reliability and statistical robustness of our estimates regarding pet exposure to SARS-CoV-2. This study on SARS-CoV-2 reaffirms the crucial importance of adopting a One Health approach incorporating domestic animals when managing an epidemic caused by a zoonotic virus.

Characterization of monoclonal antibodies targeting SARS-CoV-2 spike glycoprotein: Reactivity against Delta and Omicron BA.1 variants

The cross-species transmissibility of SARS-CoV-2 infection has necessitated development of specific reagents for detecting infection in various animal species. The spike glycoprotein of SARS-CoV-2, which is involved in viral entry, is a highly immunogenic protein. To develop assays targeting this protein, we generated eight monoclonal antibodies (mAbs) against the S1 and seven against the S1/S2 protein (ectodomain) of SARS CoV-2. Based on neutralization capability and reactivity profile observed in ELISA, the mAbs generated against the S1/S2 antigen exhibited a broader spectrum of epitope specificity than those produced against the S1 domain alone. The full-length ectodomain induced antibodies that could neutralize the two most important variants of the virus encountered during the pandemic, namely Delta and Omicron. The availability of these reagents could greatly enhance the development of precise diagnostics for detecting COVID-19 infections in various host species and contribute to the advancement of mAb-based therapeutics.

First detection of Omicron variant BA.4.1 lineage in dogs, Chile

SARS-CoV-2's rapid global spread caused the declaration of COVID-19 as a pandemic in March 2020. Alongside humans, domestic dogs and cats are also susceptible to infection. However, limited reports on pet infections in Chile prompted a comprehensive study to address this knowledge gap. Between March 2021 and March 2023, the study assessed 65 pets (26 dogs and 39 cats) from 33 COVID-19+ households alongside 700 nasal swabs from animals in households with unknown COVID-19 status. Using RT-PCR, nasal, fecal, and environmental samples were analyzed for the virus. In COVID-19+ households, 6.06% tested positive for SARS-CoV-2, belonging to 3 dogs, indicating human-to-pet transmission. Pets from households with unknown COVID-19 status tested negative for the virus. We obtained 2 SARS-CoV-2 genomes from animals, that belonged to Omicron BA.4.1 variant, marking the first report of pets infected with this lineage globally. Phylogenetic analysis showed these sequences clustered with human sequences collected in Chile during the same period when the BA.4.1 variant was prevalent in the country. The prevalence of SARS-CoV-2 in Chilean pets was relatively low, likely due to the country's high human vaccination rate. Our study highlights the importance of upholding and strengthening human vaccination strategies to mitigate the risk of interspecies transmission. It underscores the critical role of the One Health approach in addressing emerging zoonotic diseases, calling for further research on infection dynamics and risk factors for a comprehensive understanding.

Risk assessment of SARS-CoV-2 replicating and evolving in animals

The retransmissions of SARS-CoV-2 from several mammals - primarily mink and white-tailed deer - to humans have raised concerns for the emergence of a new animal-derived SARS-CoV-2 variant to worsen the pandemic. Here, we discuss animal species that are susceptible to natural or experimental infection with SARS-CoV-2 and can transmit the virus to mates or humans. We describe cutting-edge techniques to assess the impact of a mutation in the viral spike (S) protein on its receptor and on antibody binding. Our review of spike sequences of animal-derived viruses identified nine unique amino acid exchanges in the receptor-binding domain (RBD) that are not present in any variant of concern (VOC). These mutations are present in SARS-CoV-2 found in companion animals such as dogs and cats, and they exhibit a higher frequency in SARS-CoV-2 found in mink and white-tailed deer, suggesting that sustained transmissions may contribute to maintaining novel mutations. Four of these exchanges, such as Leu452Met, could undermine acquired immune protection in humans while maintaining high affinity for the human angiotensin-converting enzyme 2 (ACE2) receptor. Finally, we discuss important avenues of future research into animal-derived viruses with public health risks.

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.

A comparative study of eight serological methods shows that spike protein-based ELISAs are the most accurate tests for serodiagnosing SARS-CoV-2 infections in cats and dogs

Introduction

Coronavirus disease 2019 (COVID-19) is an infectious zoonotic disease caused by SARS-CoV-2. Monitoring the infection in pets is recommended for human disease surveillance, prevention, and control since the virus can spread from people to animals during close contact. Several diagnostic tests have been adapted from humans to animals, but limited data on the validation process are available.

Methods

Herein, the first comparative study of six "in house" and two commercial serological tests developed to monitor SARS-CoV-2 infection in pets was performed with a well-coded panel of sera (61 cat sera and 74 dog sera) with a conservative criterion (viral seroneutralisation and/or RT-qPCR results) as a reference. Four "in house" tests based on either the RBD fragment of the spike protein (RBD-S) or the N-terminal fragment of the nucleoprotein (N) were developed for the first time. The analytical specificity (ASp) of those tests that showed the best diagnostic performance was assessed. The validation included the analysis of a panel of sera obtained pre-pandemic from cats and dogs infected with other coronaviruses to determine the analytical Sp (17 cat sera and 41 dog sera).

Results and discussion

ELISAS based on the S protein are recommended in serosurveillance studies for cats (RBD-S SALUVET ELISA, ELISA COVID UNIZAR and INgezim® COVID 19 S VET) and dogs (INgezim® COVID 19 S VET and RBD-S SALUVET ELISA). These tests showed higher diagnostic sensitivity (Se) and DSp in cats (>90%) than in dogs. When sera obtained prior to the pandemic and from animals infected with other coronaviruses were analyzed by RBD-S and N SALUVET ELISAs and INgezim® COVID 19 S VET, a few cross reactors or no cross reactions were detected when dog and cat sera were analyzed by tests based on the S protein, respectively. In contrast, the number of cross reactions increased when the test was based on the N protein. Thus, the use of tests based on the N protein was discarded for serodiagnosis purposes. The results obtained revealed the most accurate serological tests for each species. Further studies should attempt to improve the diagnostic performance of serological tests developed for dogs.

Clinical and epidemiologic features of SARS-CoV-2 in dogs and cats compiled through national surveillance in the United States

OBJECTIVE

To characterize clinical and epidemiologic features of SARS-CoV-2 in companion animals detected through both passive and active surveillance in the US.

ANIMALS

204 companion animals (109 cats, 95 dogs) across 33 states with confirmed SARS-CoV-2 infections between March 2020 and December 2021.

PROCEDURES

Public health officials, animal health officials, and academic researchers investigating zoonotic SARS-CoV-2 transmission events reported clinical, laboratory, and epidemiologic information through a standardized One Health surveillance process developed by the CDC and partners.

RESULTS

Among dogs and cats identified through passive surveillance, 94% (n = 87) had reported exposure to a person with COVID-19 before infection. Clinical signs of illness were present in 74% of pets identified through passive surveillance and 27% of pets identified through active surveillance. Duration of illness in pets averaged 15 days in cats and 12 days in dogs. The average time between human and pet onset of illness was 10 days. Viral nucleic acid was first detected at 3 days after exposure in both cats and dogs. Antibodies were detected starting 5 days after exposure, and titers were highest at 9 days in cats and 14 days in dogs.

CLINICAL RELEVANCE

Results of the present study supported that cats and dogs primarily become infected with SARS-CoV-2 following exposure to a person with COVID-19, most often their owners. Case investigation and surveillance that include both people and animals are necessary to understand transmission dynamics and viral evolution of zoonotic diseases like SARS-CoV-2.

Risk Factors for SARS-CoV-2 Infection and Illness in Cats and Dogs1

We tested swab specimens from pets in households in Ontario, Canada, with human COVID-19 cases by quantitative PCR for SARS-CoV-2 and surveyed pet owners for risk factors associated with infection and seropositivity. We tested serum samples for spike protein IgG and IgM in household pets and also in animals from shelters and low-cost neuter clinics. Among household pets, 2% (1/49) of swab specimens from dogs and 7.7% (5/65) from cats were PCR positive, but 41% of dog serum samples and 52% of cat serum samples were positive for SARS-CoV-2 IgG or IgM. The likelihood of SARS-CoV-2 seropositivity in pet samples was higher for cats but not dogs that slept on owners’ beds and for dogs and cats that contracted a new illness. Seropositivity in neuter-clinic samples was 16% (35/221); in shelter samples, 9.3% (7/75). Our findings indicate a high likelihood for pets in households of humans with COVID-19 to seroconvert and become ill.

Pulmonary fibrosis in a dog as a sequela of infection with Severe Acute Respiratory Syndrome Coronavirus 2? A case report

Background

Interstitial lung disease is a heterogeneous group of conditions characterized by severe radiographic changes and clinicopathological findings. However, in the vast majority of cases, the cause remains unknown.

Case description

In the present study, we reported the clinical case of a 3 years old female Bull Terrier presented in October 2020 to the Advanced Diagnostic Imaging Department of the Turin Veterinary Teaching Hospital with a progressive pulmonary illness characterized by dyspnea, exercise intolerance, and a diffuse and severe pulmonary interstitial pattern at imaging investigations.

Considering the clinical findings, the dog was included in a serological survey for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection in companion animals, showing positive results. Due to the further clinical worsening, the owners opted for euthanasia. At necroscopy, dog showed severe and chronic bronchopneumonia compatible with a Canine Idiopathic Pulmonary Fibrosis and with serological features linked to a SARS-CoV-2 infection.

Conclusions

The comparison of these lesions with those reported in humans affected by Coronavirus Disease 2019 (COVID-19) supports the hypothesis that these findings may be attributable to the post-acute sequelae of SARS-CoV-2 infection in a dog with breed predisposition to Canine Idiopathic Pulmonary Fibrosis (CIPF), although direct evidence of SARS-CoV-2 by molecular or antigenic approaches remained unsolved.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03191-x.

Experimental and natural infections of severe acute respiratory syndrome-related coronavirus 2 in pets and wild and farm animals

The severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) has spread globally and has led to extremely high mortality rates. In addition to infecting humans, this virus also has infected animals. Experimental studies and natural infections showed that dogs have a low susceptibility to SARS-CoV-2 infection, whereas domesticated cats and other animals in the family Felidae, such as lions, tigers, snow leopards, and cougars, have a high susceptibility to viral infections. In addition, wild white-tailed deer, gorillas, and otters have been found to be infected by SARS-CoV-2. Furry farm animals, such as minks, have a high susceptibility to SARS-CoV-2 infection. The virus appears to spread among minks and generate several new mutations, resulting in increased viral virulence. Furthermore, livestock animals, such as cattle, sheep, and pigs, were found to have low susceptibility to the virus, whereas chicken, ducks, turkeys, quail, and geese did not show susceptibility to SARS-CoV-2 infection. This knowledge can provide insights for the development of SARS-CoV-2 mitigation strategies in animals and humans. Therefore, this review focuses on experimental (both replication and transmission) in vitro, ex vivo, and in vivo studies of SARS-CoV-2 infections in pets and in wild and farm animals, and to provide details on the mechanism associated with natural infection.

Susceptibility of Pets to SARS-CoV-2 Infection: Lessons from a Seroepidemiologic Survey of Cats and Dogs in Portugal

Betacoronavirus (β-CoV) are positive single-stranded RNA viruses known to infect mammals. In 2019, a novel zoonotic β-CoV emerged, the severe acute respiratory syndrome (SARS)-CoV-2. Although the most frequent SARS-CoV-2 transmission route is within humans, spillover from humans to domestic and wild animals has been reported, including cats (Felis catus), dogs (Canis lupus familiaris), and minks (Neovision vision). In order to understand the potential role of domestic animals in SARS-CoV-2 global transmission, as well their susceptibility to infection, a seroepidemiologic survey of cats and dogs in Portugal was conducted. Antibodies against SARS-CoV-2 were detected in 15/69 (21.74%) cats and 7/148 (4.73%) dogs. Of the SARS-CoV-2 seropositive animals, 11/22 (50.00%) were possibly infected by human-to-animal transmission, and 5/15 (33.33%) cats were probably infected by cat-to-cat transmission. Moreover, one dog tested positive for SARS-CoV-2 RNA. Data suggest that cats and dogs are susceptible to SARS-CoV-2 infection in natural conditions. Hence, a one-health approach is crucial in the SARS-CoV-2 pandemic to understand the risk factors beyond infection in a human-animal environment interface.

Emerging Trends in the Epidemiology of COVID-19: The Croatian 'One Health' Perspective

During the four pandemic waves, a total of 560,504 cases and 10,178 deaths due to COVID-19 were reported in Croatia. The Alpha variant, dominant from March 2021 (>50% of positive samples), was rapidly replaced by Delta variants (>90%) by August 2021. Several seroprevalence studies were conducted in different populations (general population, children/adolescents, professional athletes, healthcare workers, veterinarians) and in immunocompromised patients (hemodialysis patients, liver/kidney transplant recipients). After the first pandemic wave, seroprevalence rates of neutralizing (NT) antibodies were reported to be 0.2-5.5%. Significantly higher seropositivity was detected during/after the second wave, 2.6-18.7%. Two studies conducted in pet animals (February-June 2020/July-December 2020) reported SARS-CoV-2 NT antibodies in 0.76% of cats and 0.31-14.69% of dogs, respectively. SARS-CoV-2 NT antibodies were not detected in wildlife. Environmental samples taken in the households of COVID-19 patients showed high-touch personal objects as most frequently contaminated (17.3%), followed by surfaces in patients' rooms (14.6%), kitchens (13.3%) and bathrooms (8.3%). SARS-CoV-2 RNA was also detected in 96.8% affluent water samples, while all effluent water samples tested negative. Detection of SARS-CoV-2 in humans, animals and the environment suggests that the 'One Health' approach is critical to controlling COVID-19 and future pandemics.

Near-Complete Genome of SARS-CoV-2 Delta (AY.3) Variant Identified in a Dog in Kansas, USA

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) descriptions of infection and transmission have been increasing in companion animals in the past year. Although canine susceptibility is generally considered low, their role in the COVID-19 disease cycle remains unknown. In this study, we detected and sequenced a delta variant (AY.3) from a 12-year-old Collie living with owners that previously tested positive for SARS-CoV-2. It is unclear if the dogs' symptoms were related to SARS-CoV-2 infection or underlying conditions. The whole genome sequence obtained from the dog sample had several unique consensus level changes not previously identified in a SARS-CoV-2 genome that may play a role in the rapid adaptation from humans to dogs. Within the spike coding region, 5/7 of the subconsensus variants identified in the dog sequence were also identified in the closest in-house human reference case. Taken together, the whole genome sequence, and phylogenetic and subconsensus variant analyses indicate the virus infecting the animal originated from a local outbreak cluster. The results of these analyses emphasize the importance of rapid detection and characterization of SARS-CoV-2 variants of concern in companion animals.

Report of One-Year Prospective Surveillance of SARS-CoV-2 in Dogs and Cats in France with Various Exposure Risks: Confirmation of a Low Prevalence of Shedding, Detection and Complete Sequencing of an Alpha Variant in a Cat

Despite the probable zoonotic origin of SARS-CoV-2, only limited research efforts have been made to understand the role of companion animals in SARS-CoV-2 epidemiology. According to recent serological prevalence studies, human-to-companion animal transmission is quite frequent, which led us to consider that the risk of SARS-CoV-2 transmission from animal to human, albeit negligible in the present context, may have been underestimated. In this study, we provide the results of a prospective survey that was conducted to evaluate the SARS-CoV-2 isolation rate by qRT-PCR in dogs and cats with different exposure risks and clinical statuses. From April 2020 to April 2021, we analyzed 367 samples and investigated the presence of SARS-CoV-2 RNA using qRT-PCR. Only four animals tested positive, all of them being cats. Three cats were asymptomatic and one presented a coryza-like syndrome. We describe in detail the infection in two cats and the associated clinical characteristics. Importantly, we obtained SARS-CoV-2 genomes from one infected animal and characterized them as Alpha variants. This represents the first identification of the SARS-CoV-2 Alpha variant in an infected animal in France.