Presence of Antibodies to SARS-CoV-2 in Domestic Cats in Istanbul, Turkey, Before and After COVID-19 Pandemic

SARS-CoV-2 Seroprevalence in Indoor House Cats From the Lisbon Area During the COVID-19 Pandemic, 2019-2021

The susceptibility of various animal species to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been studied extensively. Cats have garnered significant concern due to their high susceptibility and proximity to humans. This study aimed to evaluate the susceptibility and antibody response in house cats exposed to SARS-CoV-2 when human infection was spreading in the Lisbon area during the 2019-2021 period. A total of 733 serum samples were collected and characterized from cats admitted to the Veterinary Teaching Hospital of the Faculty of Veterinary Medicine at the University of Lisbon (HEV-FMV-ULisboa). All samples were tested by enzyme-linked immunosorbent assay (ELISA) for immunoglobulin M (IgM) and immunoglobulin G (IgG) anti-SARS-CoV-2 whole Spike and receptor-binding domain (RBD) proteins from the Wuhan-Hu-1 isolate and 14.7% (108/733) tested positive, suggesting exposure to the human virus. Surrogate virus neutralization test (sVNT) against the Wuhan-Hu-1 isolate showed that 20.4% of ELISA positive samples (22/108) harbored neutralizing antibodies against the virus. The 22 most promising serum samples were retested using ELISA and sVNT against Alpha, Delta, and Omicron SARS-CoV-2 variants. Notably, these samples exhibited antibodies that were capable of recognizing and neutralizing these variants. Subsequent neutralization assays confirmed that the serum samples effectively inhibited the infection process of Wuhan-Hu-1 D614G, Delta, and Omicron SARS-CoV-2 pseudotyped viruses. Our findings indicate that cats were exposed to SARS-CoV-2 infection during the pandemic period and generated highly effective and broadly neutralizing antibodies against the virus. Although cats have not been demonstrated to significantly contribute to the spread of SARS-CoV-2, their high susceptibility to asymptomatic infection underscores the importance of investment in preventive surveillance measures. In summary, our study reinforces the notion that cats naturally infected with SARS-CoV-2 represent a valuable anthroponotic disease model in house settings and might be a potential source for the development of antibodies against SARS-CoV-2 in tackling future outbreaks with a One Heath perspective.

Brain invasion of bovine coronavirus: molecular analysis of bovine coronavirus infection in calves with severe pneumonia and neurological signs

IMPORTANCE

Although the role of bovine coronavirus (BCoV) in calf diarrhea and respiratory disorders is well documented, its contribution to neurological diseases is unclear.

OBJECTIVE

This study conducted virological investigations of calves showing diarrhea and respiratory and neurological signs.

METHODS

An outbreak of diarrhea, respiratory, and neurological disorders occurred among the 12 calves in July 2022 in Istanbul, Türkiye. Two of these calves exhibited neurological signs and died a few days after the appearance of symptoms. One of these calves was necropsied and analyzed using molecular and histopathological tests.

RESULTS

BCoV RNA was detected in the brain, lung, spleen, liver, and intestine of the calf that had neurological signs by real-time reverse transcription polymerase chain reaction. Immunostaining was also observed in the intestine and brain. A 622 bp S1 gene product was noted on gel electrophoresis only in the brain. Phylogenetic analysis indicated that the BCoV detected in this study had a high proximity to the BCoV strain GIb with 99.19% nucleotide sequence homology to the strains detected in Poland, Israel, Türkiye, and France. No distinct genetic lineages were observed when the brain isolate was compared with the respiratory and enteric strains reported to GenBank. In addition, the highest identity (98,72%) was obtained with the HECV 4408 and L07748 strains of human coronaviruses.

CONCLUSIONS AND RELEVANCE

The strain detected in a calf brain belongs to the GIb-European lineage and shares high sequence homology with BCoV strains detected in Europe and Israel. In addition, the similarity between the human coronaviruses (4408 and L07748) raises questions about the zoonotic potential of the strains detected in this study.

Assessment of the Risk Impact of SARS-CoV-2 Infection Prevalence between Cats and Dogs in America and Europe: A Systematic Review and Meta-Analysis

The COVID-19 pandemic represented a huge obstacle for public health and demonstrated weaknesses in surveillance and health promotion systems around the world. Its etiological agent, SARS-CoV-2, of zoonotic origin, has been the target of several studies related to the control and prevention of outbreaks and epidemics of COVID-19 not only for humans but also for animals. Domestic animals, such as dogs and cats, have extensive contact with humans and can acquire the infection both naturally and directly from humans. The objective of this article was to summarize the seroprevalence findings of SARS-CoV-2 in dogs and cats and correlate them with the strength of infection risk between each of them. This is a systematic review and meta-analysis following the recommendations of PRISMA 2020. The search and selection of papers was carried out using in vivo experimental works with animals using the descriptors (MeSH/DeCS) "Animal", "Public Health", "SARS-CoV-2" and "Pandemic" (together with AND) in English, Portuguese or Spanish for Science Direct, PUBMED, LILACS and SciELO databases. The ARRIVE checklist was used for methodological evaluation and the Comprehensive Meta-Analysis v2.2 software with the Difference Risk (RD) test to evaluate statistical inferences (with subgroups by continent). Cats showed greater susceptibility to SARS-CoV-2 compared to dogs both in a joint analysis of studies (RD = 0.017; 95% CI = 0.008-0.025; p < 0.0001) and in the American subgroup (RD = 0.053; 95% CI = 0.032-0.073; p < 0.0001), unlike the lack of significant difference on the European continent (RD = 0.009; 95% CI = -0.001-0.018; p = 0.066). Therefore, it was observed that cats have a greater interest in health surveillance due to the set of biological and ecological aspects of these animals, but also that there are a set of factors that can influence the spread and possible spillover events of the virus thanks to the anthropozoonotic context.

Serological Evidence of SARS-CoV-2 Exposure in Domestic Dogs and Cats, Thailand: Detection of SARS-CoV-2 Omicron Variant in Dogs Living in COVID-19-Positive Households

SARS-CoV-2 causes the coronavirus disease 2019 (COVID-19) pandemic. Cross-species transmission of SARS-CoV-2 from humans to domestic animals has been reported. In this study, we conducted a serological survey and molecular investigation of SARS-CoV-2 infection in domestic dogs and cats in Bangkok and the vicinities from January 2021 to August 2022. A total of 2,664 serum samples were examined for antibodies against SARS-CoV-2 using nucleocapsid protein-based ELISA (NP-ELISA). Our result showed 2.28% (33/1,446) seropositivity in dogs and 1.81% (22/1,218) in cats. The positive NP-ELISA serum samples were confirmed using a surrogate virus neutralization test (sVNT). Of 55 seropositive samples by NP-ELISA, two dogs and 19 cats were confirmed seropositive by sVNT. Our result supported the serological evidence of SARS-CoV-2 exposure in domestic dogs and cats. We also investigated SARS-CoV-2 infection by real-time RT-PCR in 156 domestic dogs and cats in COVID-19-positive households. Our result showed active SARS-CoV-2 infection in a dog living with COVID-19 positive owner. Genetic and phylogenetic analysis of the SARS-CoV-2 from the dog and its owner confirmed the SARS-CoV-2 variant Omicron BA.2. It is the first report of SARS-CoV-2 Omicron variant in pet living in COVID-19-positive household in Thailand.

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.

A retrospective study showing a high rate of seropositivity against SARS-CoV-2 in wild felines in India

We report a high rate of seropositivity against SARS-CoV-2 in wild felines in India. Seropositivity was determined by microneutralization and plaque reduction neutralization assays in captive Asiatic lions, leopards, and Bengal tigers. The rate of seropositivity was positively correlated with that of the incidence in humans, suggesting the occurrence of large spillover events.

A one-year extensive molecular survey on SARS-CoV-2 in companion animals of Turkey shows a lack of evidence for viral circulation in pet dogs and cats

Current evidence have now demonstrated that SARS-CoV-2 infects a wide array of mammalian animals; however, the full range of hosts and the viral circulation in companion animals remains to be clarified. In this context, as no such evidenced cases have been reported from Turkey, we aimed to screen for SARS-CoV-2 nucleic acid in housed dogs and cats clinically evaluated for respiratory symptoms and reared in different locations of Samsun province in the black sea region of Turkey from July 2020 to July 2021. Nasal swabs were collected from a total of 415 pets (65 cats and 350 dogs) aged between 1 and 9 years old. All the specimens were tested for SARS-CoV-2 RNA presence by real-time RT-PCR targeting two genomic regions of SARS-CoV-2, but none showed positive results. Our findings suggest that SARS-CoV-2 does not circulate in local pets and is not responsible for respiratory symptoms. However, further comprehensive molecular and serological surveys are required to have a better picture of the zoonotic, reverse zoonotic and pathogenic consequences of the ongoing COVID-19 pandemic in Turkey.

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.

Serological Investigation on the Presence of Feline Coronavirus (FCoV) and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Domestic Cats Living with COVID-19 Positive Owners in the UAE, 2022

Feline coronavirus (FCoV) is widely circulating among domestic cats (Felis catus). The zoonotic origin of the emerged severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and the biological characteristics of CoVs, including the ability to cross interspecies barriers, facilitate its emergence in different animals, including cats' populations. The current study is the first to report the serological investigation on the presence of FCoV and SARS-CoV-2 in domestic cats living with COVID-19-positive owners in the UAE. A total of 83 sera were collected from domestic cats living with COVID-19-positive owners (by RT-qPCR). The cats were sampled during the period between February and May 2022 in Al-Ain and Abu Dhabi Cities, UAE. Detection of FCoV and SARS-CoV-2 was carried out by enzyme-linked immunosorbent assay (ELISA). FCoV antibodies were detected in 54 samples (65%). The frequencies of FCoV were significantly higher in purebred cats (48%; 40/83) and in the cat group with outdoor access (49.4%; 41/83). SARS-CoV-2 seroprevalence in collected sera revealed 8 samples (9.6%) with positive results. Four samples (4.8%) showed positive results for both FCoV and SARS-CoV-2 antibodies. In conclusion, FCoV is widely circulating within cats' populations involved in the study. The antibodies for SARS-CoV-2 were detected in cats' populations but at a low prevalence rate. COVID-19-positive people should avoid close contact with their cats. Future serological testing of large cats' populations is crucial for providing a good understanding of COVID-19 dynamics in cats.

Human ELISA Detects anti-SARS-CoV-2 Antibodies in Cats: Seroprevalence and Risk Factors for Virus Spread in Domestic and Stray Cats in Bulgaria

The aim of this study was to verify whether the human DR-ELISA for the detection of anti-SARS-CoV-2 antibodies can be applied in cats, and to assess the risk factors that determine the spread of the virus among the cat population in Bulgaria. The study included 92 serum samples collected from 68 domestic and 24 stray cats aged from 3 months to 20 years of age in the period of January-June 2021. The samples originated from three regions in Bulgaria and from three places of inhabitance. DR-ELISA based on peroxidase-labeled SARS-CoV-2 N protein was employed to detect IgA, IgG and IgM antibodies in the samples. Subsequently, the results were compared with a commercially available multi-species ELISA kit. There was high seroprevalence (83.33%) in stray cats and 41.18% in domestic cats, confirmed by the human and veterinary ELISA kit. The positive cases in the regional cities were 42.86%, in small towns 50% and in villages 78.26%. Cats under 7 years had a five times higher risk than those over 7 years (p = 0.001). The risk was seven times higher for stray cats than for domestic cats (p = 0.001). In addition, the results indicate that the risk was the highest for cats in villages (p = 0.006) compared to cats in other places of inhabitance. This study demonstrates that human DR-ELISA may be successfully applied to monitor the circulation of SARS-CoV-2 in cats and other susceptible species. Cats might serve as sentinel animals for tracking the virus in nature and in inhabited areas (strays) and to discover asymptomatic cases in humans/owners.

Guest edited collection serological study of SARS-CoV-2 antibodies in japanese cats using protein-A/G-based ELISA

BACKGROUND

Little is known about the epidemic status of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in cats in Japan due to insufficiently reliable seroepidemiological analysis methods that are easy to use in cats.

RESULTS

We developed a protein-A/G-based enzyme-linked immunosorbent assay (ELISA) to detect antibodies against SARS-CoV-2 in cats. The assay was standardized using positive rabbit antibodies against SARS-CoV-2. The ELISA results were consistent with those of a conventional anti-feline-immunoglobulin-G (IgG)-based ELISA. To test the protein-A/G-based ELISA, we collected blood samples from 1,969 cats that had been taken to veterinary clinics in Japan from June to July 2020 and determined the presence of anti-SARS-CoV-2 antibodies. Nine cats were found to have SARS-CoV-2 S1-specific IgG, of which 4 had recombinant receptor-binding domain-specific IgG. Of those 9 samples, one showed neutralizing activity. Based on these findings, we estimated that the prevalence of SARS-CoV-2 neutralizing antibodies in cats in Japan was 0.05% (1/1,969 samples). This prevalence was consistent with the prevalence of neutralizing antibodies against SARS-CoV-2 in humans in Japan according to research conducted at that time.

CONCLUSIONS

Protein-A/G-based ELISA has the potential to be a standardized method for measuring anti-SARS-CoV-2 antibodies in cats. The infection status of SARS-CoV-2 in cats in Japan might be linked to that in humans.

Development of in House ELISAs to Detect Antibodies to SARS-CoV-2 in Infected and Vaccinated Humans by Using Recombinant S, S1 and RBD Proteins

(1) Background: The aim of this study was to produce in-house ELISAs which can be used to determine SARS-CoV-2-specific antibody levels directed against the spike protein (S), the S1 subunit of S and the receptor binding domain (RBD) of S in SARS-CoV-2 vaccinated and infected humans. (2) Methods: Three in-house ELISAs were developed by using recombinant proteins of SARS-CoV-2, namely the S, S1 and RBD proteins. Specificity and sensitivity evaluations of these tests were performed using sera from SARS-CoV-2-infected (n = 70) and SARS-CoV-2-vaccinated (n = 222; CoronaVac vaccine) humans in Istanbul, Turkey. The analyses for the presence of SARS-CoV-2-specific antibodies were performed using the in-house ELISAs, a commercial ELISA (Abbott) and a commercial surrogate virus neutralization test (sVNT). We also analyzed archival human sera (n = 50) collected before the emergence of COVID-19 cases in Turkey. (3) Results: The sensitivity of the in-house S, S1 and RBD ELISAs was found to be 88.44, 90.17 and 95.38%, while the specificity was 72.27, 89.08 and 89.92%, respectively, when compared to the commercial SARS-CoV-2 antibody test kit. The area under curve (AUC) values were 0.777 for the in-house S ELISA, 0.926 for the S1 ELISA, and 0.959 for the RBD ELISA. The kappa values were 0.62, 0.79 and 0.86 for the S, S1 and RBD ELISAs, respectively. (4) Conclusions: The in-house S1 and RBD ELISAs developed in this study have acceptable performance characteristics in terms of sensitivity, specificity, AUC and kappa values. In particular, the RBD ELISA seems viable to determine SARS-CoV-2-specific antibody levels, both in infected and vaccinated people, and help mitigate SARS-CoV-2 outbreaks and spread.

A cross-sectional serosurvey of SARS-CoV-2 and co-infections in stray cats from the second wave to the sixth wave of COVID-19 outbreaks in Spain

Severe Acute Respiratory Syndrome Coronavirus 2 is the causative agent of Coronavirus Disease 2019 in humans. Among domestic animals, cats are more susceptible to SARS-CoV-2 than dogs. The detection of anti-SARS-CoV-2 antibodies in seemingly healthy cats and/or infected cats which are in close contact with infected humans has been described. The presence of animals that tested positive by serology or molecular techniques could represent a potential transmission pathway of SARS-CoV-2 that can spill over into urban wildlife. This study analyses the seroprevalence variation of SARS-CoV-2 in stray cats from different waves of outbreaks in a geographical area where previous seroepidemiological information of SARS-CoV-2 was available and investigate if SARS-CoV-2-seropositive cats were exposed to other co-infections causing an immunosuppressive status and/or a chronic disease that could lead to a SARS-CoV-2 susceptibility. For this purpose, a total of 254 stray cats from Zaragoza (Spain) were included. This analysis was carried out by the enzyme-linked immunosorbent assay using the receptor binding domain of Spike antigen and confirmed by serum virus neutralization assay. The presence of co-infections including Toxoplasma gondii, Leishmania infantum, Dirofilaria immitis, feline calicivirus, feline herpesvirus type 1, feline leukemia virus and feline immunodeficiency virus, was evaluated using different serological methods. A seropositivity of 1.57% was observed for SARS-CoV-2 including the presence of neutralizing antibodies in three cats. None of the seropositive to SARS-CoV-2 cats were positive to feline coronavirus, however, four SARS-CoV-2-seropositive cats were also seropositive to other pathogens such as L. infantum, D. immitis and FIV (n = 1), L. infantum and D. immitis (n = 1) and L. infantum alone (n = 1).Considering other pathogens, a seroprevalence of 16.54% was detected for L. infantum, 30.31% for D. immitis, 13.78%, for T. gondii, 83.86% for feline calicivirus, 42.52% for feline herpesvirus type 1, 3.15% for FeLV and 7.87% for FIV.

Our findings suggest that the epidemiological role of stray cats in SARS-CoV-2 transmission is scarce, and there is no increase in seropositivity during the different waves of COVID-19 outbreaks in this group of animals. Further epidemiological surveillances are necessary to determine the risk that other animals might possess even though stray cats do not seem to play a role in transmission.

Seroprevalence of SARS-CoV-2 in Client-Owned Cats from Portugal

The close contact between humans and domestic cats raises concerns about the potential risks of SARS-CoV-2 transmission. Thus, this study aims to investigate anti-SARS-CoV-2 seroprevalence in client-owned cats from Portugal and evaluate the infection risk of cats that maintain contact with human COVID-19 cases. A total of 176 cats, belonging to 94 households, were sampled. Cat owners answered an online questionnaire, and cats were screened for antibodies against SARS-CoV-2 using a commercial ELISA. Twenty (21.3%) households reported at least one confirmed human COVID-19 case. Forty cats (22.7%) belonged to a COVID-19-positive and 136 (77.3%) to a COVID-19-negative household. The seroprevalences of cats from COVID-19-positive and -negative households were 5.0% (2/40) and 0.7% (1/136). The two SARS-CoV-2-seropositive cats from COVID-19-positive households had an indoor lifestyle, and their owners stated that they maintained a close and frequent contact with them, even after being diagnosed with COVID-19, pointing towards human-to-cat transmission. The SARS-CoV-2-seropositive cat from the COVID-19-negative household had a mixed indoor/outdoor lifestyle and chronic diseases. Owners of the three SARS-CoV-2-seropositive cats did not notice clinical signs or behavior changes. This study highlights the low risk of SARS-CoV-2 transmission from COVID-19-positive human household members to domestic cats, even in a context of close and frequent human-animal contact.

Clinical, virological, imaging and pathological findings in a SARS CoV-2 antibody positive cat

This paper reports a presumptive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in a cat. A cat with respiratory disease living with three individuals with coronavirus disease 2019 showed bilateral ground-glass opacities in the lung on X-ray and computed tomography. The clinical swabs were negative for SARS-CoV-2 RNA, but the serum was positive for SARS-CoV-2 antibodies. Interstitial pneumonia and prominent type 2 pneumocyte hyperplasia were noted on histopathology. Respiratory tissues were negative for SARS-CoV-2 RNA or antigen, but the cat was positive for feline parvovirus DNA. In conclusion, the respiratory disease and associated pathology in this cat could have been due to exposure to SARS-CoV-2.