Household Transmission of SARS-CoV-2 from Humans to Pets, Washington and Idaho, USA

Chemical Sensors and Biosensors for Point-of-Care Testing of Pets: Opportunities for Individualized Diagnostics of Companion Animals

Point-of-care testing (POCT) is recognized as one of the most disruptive medical technologies for rapid and decentralized diagnostics. Successful commercial examples include portable glucose meters, pregnancy tests, and COVID-19 self-tests. However, compared to advancements in human healthcare, POCT technologies for companion animals (pets) remain significantly underdeveloped. This Review explores the latest advancements in pet POCT and examines the challenges and opportunities in the field for individualized diagnostics of cats and dogs. The most frequent diseases and their respective biomarkers in blood, urine, and saliva are discussed. We examine key strategies for developing the next-generation POCT devices by harnessing the potential of selective (bio)receptors and high-performing transducers such as lateral flow tests and electrochemical (bio)sensors. We also present the most recent research initiatives and the successful commercial pet POCT technologies. We discuss future trends in the field, such the role of biomarker discovery and development of wearable, implantable, and breath sensors. We believe that advancing pet POCT technologies benefits not only animals but also humans and the environment, supporting the One Health approach.

High SARS-CoV-2 Exposure in Feline Residents of a Cat Café in Texas, United States, 2021-2022

Congregate animal settings can serve as foci for the increased transmission of pathogens, including zoonoses. Domestic cats have been shown to be reservoirs for SARS-CoV-2 but the public health importance of infected cats has not yet been determined. A population of indoor-only residential cats at a cat café in central Texas with a high level of human interaction was evaluated for infection with SARS-CoV-2 in a longitudinal study in 2021-2022. Among 25 cats, none were qRT-PCR-positive, while 50% harbored SARS-CoV-2-neutralizing antibodies, including 1 that remained seropositive for >8 months. The high level of human exposure in this unique congregate cat setting-in which dozens of new visitors interact with the cats every day-likely facilitated the human-to-cat transmission of SARS-CoV-2 that led to a 50% infection prevalence in cats. This work was conducted when the Delta and Omicron variants predominated. Given that feline susceptibility to infection and shedding of a virus may vary across different viral variants, veterinary surveillance may be an important component of veterinary and human health risk assessments.

Repeated detection of SARS-CoV-2 in pet dogs in Ibadan, Oyo State, Nigeria: a cause for vigilance

BACKGROUND

The COVID-19 pandemic of 2020 was unprecedented in its devastating impact on the global economy, public health, travel and tourism, education, sports, religion, and social lives. Studies conducted thereafter on the disease and its causative agent, SARS-CoV-2, have highlighted the need for effective and sustainable public health interventions.

METHODS

This study investigated the prevalence and endemicity of SARS-CoV-2 infection in pet dogs using immunochromatography assay (IC) and quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) of their blood, rectal swabs, and nasal swabs in Ibadan, Oyo State, Nigeria between 2022 and 2024.

KEY FINDINGS

For the IC, positivity rates of 11.7% (23/197), 85.7% (6/7), and 100% (3/3) were recorded for 2022, 2023 and 2024 while for the RT-qPCR, positivity rates of 37.9% (11/29), 33.3% (2/6) and 100% (3/3) were recorded for 2022, 2023 and 2024. This repeated detection of SARS-CoV-2 in three of the dogs tested over the three-year period suggests continuous shedding of the virus by these animals and indicates endemicity of the virus in the study area. Findings highlight the urgent need for optimized SARS-CoV-2 rapid diagnostic tools tailored for veterinary applications to ensure rapid and reliable detection of the virus, especially in resource-constrained settings.

CONCLUSION

Considering the zoonotic nature of SARS-CoV-2 and its potential for mutation into more virulent strains that can be transmissible to humans, the findings of this study have significant implications for public health and implementation of One Health strategies by policymakers, and highlight the need for robust SARS-CoV-2 surveillance in domestic animals to mitigate potential zoonotic risks.

SARS-CoV-2 exposure in hunting and stray dogs of southern Italy

Evidence of exposure to the pandemic SARS-CoV-2 has been described in numerous animal species, including pets, which are predisposed to coming into contact with this virus due to their close relationship with owners. It has been accepted that dogs are poorly susceptible to this virus and that seroconversion, rather than shedding, occurs following infection, which can occur directly through contact with infected owners or indirectly through environmental contamination. In this study, the seroprevalence of SARS-CoV-2 was evaluated in apparently health hunting and stray dogs of Campania region, southern Italy (sampled in September 2023). A total of 5/112 (4.5%) animals tested seropositive using two different commercial ELISAs. Stray animals had greater exposure than hunting dogs. The feces and blood of each animal were tested with a real-time PCR targeting the nucleocapsid and ORF1ab coding sequences. No animal tested positive in molecular investigations, indicating a past exposure without active infection at the time of sampling.

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.

The Transmission of SARS-CoV-2 from COVID-19-Diagnosed People to Their Pet Dogs and Cats in a Multi-Year Surveillance Project

Recent emerging zoonotic disease outbreaks, such as that of SARS-CoV-2, have demonstrated the need for wider companion animal disease surveillance. We tested 1000 dogs and cats belonging to employees of a US veterinary hospital network that were exposed to human COVID-19 cases in the household between 1 January 2020 and 10 March 2022 for SARS-CoV-2 and surveyed their owners about clinical signs and risk factors. The seropositivity was 33% for 747 dogs and 27% for 253 cats. Pet seropositivity correlated with the US human case rates over time, exhibiting peaks corresponding with the major COVID-19 surges. Antibodies persisted longer than previously documented (828 days in dogs; 650 days in cats). Increasing age and duration of proximity to infected people were associated with increased seropositivity in dogs but not cats. Cats were more likely to have clinical signs, but an association between seropositivity and the presence of clinical signs was not found in either species.

High prevalence of SARS-CoV-2 antibodies and low prevalence of SARS-CoV-2 RNA in cats recently exposed to human cases

BACKGROUND

The primary objective of this cross-sectional study, conducted in Québec and Bristish Columbia (Canada) between February 2021 and January 2022, was to measure the prevalence of viral RNA in oronasal and rectal swabs and serum antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) amongst cats living in households with at least one confirmed human case. Secondary objectives included a description of potential risk factors for the presence of SARS-CoV-2 antibodies and an estimation of the association between the presence of viral RNA in swabs as well as SARS-CoV-2 antibodies and clinical signs. Oronasal and rectal swabs and sera were collected from 55 cats from 40 households at most 15 days after a human case confirmation, and at up to two follow-up visits. A RT-qPCR assay and an ELISA were used to detect SARS-CoV-2 RNA in swabs and serum SARS-CoV-2 IgG antibodies, respectively. Prevalence and 95% Bayesian credibility intervals (BCI) were calculated, and associations were evaluated using prevalence ratio and 95% BCI obtained from Bayesian mixed log-binomial models.

RESULTS

Nine (0.16; 95% BCI = 0.08-0.28) and 38 (0.69; 95% BCI = 0.56-0.80) cats had at least one positive RT-qPCR and at least one positive serological test result, respectively. No risk factor was associated with the prevalence of SARS-CoV-2 serum antibodies. The prevalence of clinical signs suggestive of COVID-19 in cats, mainly sneezing, was 2.12 (95% BCI = 1.03-3.98) times higher amongst cats with detectable viral RNA compared to those without.

CONCLUSIONS

We showed that cats develop antibodies to SARS-CoV-2 when exposed to recent human cases, but detection of viral RNA on swabs is rare, even when sampling occurs soon after confirmation of a human case. Moreover, cats with detectable levels of virus showed clinical signs more often than cats without signs, which can be useful for the management of such cases.

Possible Spreading of SARS-CoV-2 from Humans to Captive Non-Human Primates in the Peruvian Amazon

Human-to-animal transmission events of SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) have been reported in both domestic and wild species worldwide. Despite the high rates of contagion and mortality during the COVID-19 (Coronavirus Diseases 2019) pandemic in Peru, no instances of natural virus infection have been documented in wild animals, particularly in the Amazonian regions where human-wildlife interactions are prevalent. In this study, we conducted a surveillance investigation using viral RNA sequencing of fecal samples collected from 76 captive and semi-captive non-human primates (NHPs) in the Loreto, Ucayali, and Madre de Dios regions between August 2022 and February 2023. We detected a segment of the RNA-dependent RNA polymerase (RdRp) gene of SARS-CoV-2 by metagenomic sequencing in a pooled fecal sample from captive white-fronted capuchins (Cebus unicolor) at a rescue center in Bello Horizonte, Ucayali. Phylogenetic analysis further confirmed that the retrieved partial sequence of the RdRp gene matched the SARS-CoV-2 genome. This study represents the first documented instance of molecular SARS-CoV-2 detection in NHPs in the Peruvian Amazon, underscoring the adverse impact of anthropic activities on the human-NHP interface and emphasizing the importance of ongoing surveillance for early detection and prediction of future emergence of new SARS-CoV-2 variants in animals.

Zoonosis and zooanthroponosis of emerging respiratory viruses

Lung infections in Influenza-Like Illness (ILI) are triggered by a variety of respiratory viruses. All human pandemics have been caused by the members of two major virus families, namely Orthomyxoviridae (influenza A viruses (IAVs); subtypes H1N1, H2N2, and H3N2) and Coronaviridae (severe acute respiratory syndrome coronavirus 2, SARS-CoV-2). These viruses acquired some adaptive changes in a known intermediate host including domestic birds (IAVs) or unknown intermediate host (SARS-CoV-2) following transmission from their natural reservoirs (e.g. migratory birds or bats, respectively). Verily, these acquired adaptive substitutions facilitated crossing species barriers by these viruses to infect humans in a phenomenon that is known as zoonosis. Besides, these adaptive substitutions aided the variant strain to transmit horizontally to other contact non-human animal species including pets and wild animals (zooanthroponosis). Herein we discuss the main zoonotic and reverse-zoonosis events that occurred during the last two pandemics of influenza A/H1N1 and SARS-CoV-2. We also highlight the impact of interspecies transmission of these pandemic viruses on virus evolution and possible prophylactic and therapeutic interventions. Based on information available and presented in this review article, it is important to close monitoring viral zoonosis and viral reverse zoonosis of pandemic strains within a One-Health and One-World approach to mitigate their unforeseen risks, such as virus evolution and resistance to limited prophylactic and therapeutic interventions.

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 surveillance in a veterinary health system provides insight into transmission risks

OBJECTIVE

To investigate the prevalence and seropositivity of SARS-CoV-2 in companion and exotic animals in a veterinary healthcare system.

SAMPLE

A total of 341 animals were sampled by a combination of oral and nasal swabs. Serum from whole blood was collected from a subset of animals (86 canines, 25 felines, and 6 exotic animals).

METHODS

After informed owner consent, convenience samples from client-owned animals and the pets of students and staff members associated with Colorado State University's Veterinary Health System were collected between May 2021 and September 2022. Study samples were collected by trained veterinarians, Veterinary Health System staff, and veterinary students.

RESULTS

SARS-CoV-2 RNA was detected by reverse transcription PCR in 1.6% (95% CI, 0.5% to 4.6%) of domestic canines and 1.1% (95% CI, 0.2% to 6.1%) of domestic felines. No RNA was detected in any of the exotic animal species tested (n = 66). Plaque reduction neutralization tests indicated that 12.8% (95% CI, 7.3% to 21.5%) of canines and 12.0% (95% CI, 4.2% to 30.0%) of felines had neutralizing antibodies against SARS-CoV-2.

CLINICAL RELEVANCE

This study provides insight regarding SARS-CoV-2 spillover in domestic companion and exotic animals and contributes to our understanding of transmission risk in the veterinary setting.

Assessing US Small Animal Veterinary Clinic Adaptations and Their Impacts on Workforce COVID-19 Preparedness and Response

Veterinary personnel are an essential yet often underappreciated workforce, critical for zoonotic disease prevention and response efforts that impact human health. During the early COVID-19 pandemic, the veterinary workforce supported emergency responses by promoting zoonotic disease risk communication, sharing animal health expertise, and boosting laboratory surge capacity against SARS-CoV-2 in animals and people. However, small animal veterinary workers (SAVWs), similar to healthcare workers, faced organizational challenges in providing clinical care to family pets, including those susceptible to SARS-CoV-2. We analyzed a cross-sectional survey of 1,204 SAVWs in the United States to assess veterinary clinic adaptations and their associations with SAVWs' self-perceived readiness, willingness, and ability to respond to the COVID-19 pandemic as a workforce. SAVWs who worked fewer hours than before the pandemic (ready, OR 0.59; willing, OR 0.66; able, OR 0.52) or used personal protective equipment less frequently for protection in the clinic (ready, OR 0.69; willing, OR 0.69; able, OR 0.64) felt less ready, willing, and able to respond to COVID-19. SAVWs working remotely felt less ready (OR 0.46) but not less willing or able to respond to COVID-19. Lastly, SAVWs with dependents felt less ready (OR 0.67) and able (OR 0.49) to respond to COVID-19 than SAVWs without dependents. Our findings highlight the importance of proactively managing work schedules, having access to personal protective equipment, and addressing caregiving concerns to enhance SAVW preparedness and response outcomes. SAVWs are knowledgeable, motivated personnel who should be integrated into local public health emergency preparedness and response plans, supporting a One Health framework that unites multidisciplinary teams to respond to future zoonotic disease threats.

Dogs and Cats Are Less Susceptible to the Omicron Variant of Concern of SARS-CoV-2: A Field Study in Germany, 2021/2022

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a pandemic of unprecedented extent. Besides humans, a number of animal species can be infected; however, in some species, differing susceptibilities were observed depending on the virus variant. Here, we serologically investigated cats and dogs living in households with human COVID-19 patients. The study was conducted during the transition period from delta as the dominating variant of concern (VOC) to omicron (BA.1/BA.2) to investigate the frequency of virus transmission of both VOCs from infected owners to their pets. The animal sera were tested by surrogate virus neutralization tests (sVNT) using either the original receptor-binding domain (RBD), enabling the detection of antibodies against the delta variant, or an omicron-specific RBD. Of the 290 canine samples, 20 tested positive by sVNT, but there were marked differences between the sampling time and, related thereto, the virus variants the dogs had contact to. While in November 2021, infected owners led to 50% seropositive dogs (18/36), only 0.8% (2/254) of animals with household contacts to SARS-CoV-2 between December 2021 and April 2022 tested positive. In all cases, the positive reaction was recorded against the original RBD. For cats, a similar pattern was seen, as in November 2021, 38.1% (16/42) tested positive, and between December 2021 and March 2022, only 5.0% (10/199). The markedly reduced ratio of seropositive animals during the period of omicron circulation suggests a considerably lower susceptibility of dogs and cats to this VOC. To examine the effect of further omicron subvariants, sera taken in the second and third quarter of 2022 from randomly selected cats were investigated. 2.3% (11/372) tested seropositive, and all of them showed a stronger reaction against the original RBD, further supporting the assumption of a lower susceptibility of companion animals to the omicron VOC.

Detection of SARS-CoV-2 in Terrestrial Animals in Southern Nigeria: Potential Cases of Reverse Zoonosis

Since SARS-CoV-2 caused the COVID-19 pandemic, records have suggested the occurrence of reverse zoonosis of pets and farm animals in contact with SARS-CoV-2-positive humans in the Occident. However, there is little information on the spread of the virus among animals in contact with humans in Africa. Therefore, this study aimed to investigate the occurrence of SARS-CoV-2 in various animals in Nigeria. Overall, 791 animals from Ebonyi, Ogun, Ondo, and Oyo States, Nigeria were screened for SARS-CoV-2 using RT-qPCR (n = 364) and IgG ELISA (n = 654). SARS-CoV-2 positivity rates were 45.9% (RT-qPCR) and 1.4% (ELISA). SARS-CoV-2 RNA was detected in almost all animal taxa and sampling locations except Oyo State. SARS-CoV-2 IgGs were detected only in goats from Ebonyi and pigs from Ogun States. Overall, SARS-CoV-2 infectivity rates were higher in 2021 than in 2022. Our study highlights the ability of the virus to infect various animals. It presents the first report of natural SARS-CoV-2 infection in poultry, pigs, domestic ruminants, and lizards. The close human-animal interactions in these settings suggest ongoing reverse zoonosis, highlighting the role of behavioral factors of transmission and the potential for SARS-CoV-2 to spread among animals. These underscore the importance of continuous monitoring to detect and intervene in any eventual upsurge.

"Sniffing" out SARS-CoV-2 in Arizona working dogs: an exploratory serosurvey

Susceptibility to and infection with SARS-CoV-2 in companion animals has been well-documented throughout the COVID-19 pandemic. Surveillance for the virus in dogs has largely been focused on household pets; however, other canine populations may also be impacted. We partnered with a local veterinary hospital with a high working dog patient volume to conduct viral and neutralizing antibody testing in working dogs and identify potential risk factors in the dog's work and home environments. Surveillance of SARS-CoV-2 in law enforcement and security working dogs in Arizona found 24.81% (32/129) of dogs to be seropositive. Thirteen dogs presenting with clinical signs or with reported exposure to COVID-19 in the 30 days prior to sample collection were also tested by PCR; all samples were negative. 90.7% (n = 117) of dogs were reported to be asymptomatic or have no change in performance at the time of sampling. Two dogs (1.6%) had suspected anosmia as reported by their handlers; one of which was seropositive. Known exposure to the dog's COVID-19 positive handler or household member was identified as a significant risk factor. Demographics factors including sex, altered status, and type of work were not associated with canine seropositivity. Further work is warranted to understand the impact of SARS-CoV-2 and other infectious diseases in working dogs.

Human-to-Animal Transmission of SARS-CoV-2, South Korea, 2021

To investigate SARS-CoV-2 transmission from humans to animals in Seoul, South Korea, we submitted samples from companion animals owned by persons with confirmed COVID-19. Real-time PCR indicated higher SARS-CoV-2 viral infection rates for dogs and cats than previously reported from the United States and Europe. Host-specific adaptations could introduce mutant SARS-CoV-2 to humans.

Whole-Genome Characterization of SARS-CoV-2 Reveals Simultaneous Circulation of Three Variants and a Putative Recombination (20B/20H) in Pets, Brazzaville, Republic of the Congo

Following the emergence of SARS-CoV-2, cases of pets infected with variants circulating among humans were reported. In order to evaluate the occurrence of SARS-CoV-2 circulation among pets in the Republic of the Congo, we conducted a ten-month study of dogs and cats living in COVID-19-positive households in Brazzaville and neighboring localities. Real-time PCR and the Luminex platform were used to detect SARS-CoV-2 RNA and antibodies to SARS-CoV-2 RBD and S proteins, respectively. Our results show for the first time the simultaneous circulation of several variants of SARS-CoV-2, including viruses from clades 20A and 20H and a putative recombinant variant between viruses from clades 20B and 20H. We found a high seroprevalence of 38.6%, with 14% of tested pets positive for SARS-CoV-2 RNA. Thirty-four percent of infected pets developed mild clinical signs, including respiratory and digestive signs, and shed the virus for about one day to two weeks. These results highlight the potential risk of SARS-CoV-2 interspecies transmission and the benefits of a "One Health" approach that includes SARS-CoV-2 diagnosis and surveillance of viral diversity in pets. This approach aims to prevent transmission to surrounding wildlife as well as spillback to humans.

Do Blood Phenotypes of Feline AB Blood Group System Affect the SARS-CoV-2 Antibody Serostatus in Cats?

Cats are susceptible to coronavirus infections, including infection by human severe acute respiratory syndrome coronavirus (SARS-CoV). In human ABO system blood groups, alloantibodies can play a direct role in resistance to infectious diseases. Individuals with the AB blood type were over-represented in the SARS-CoV-2 infection group. Blood type AB individuals lack both anti-A and anti-B antibodies, and therefore lack the protective effect against SARS-CoV-2 infection given by these antibodies. Starting from this knowledge, this pilot preliminary study evaluated a possible association between feline blood phenotypes A, B, and AB and serostatus for SARS-CoV-2 antibodies in cats. We also investigated selected risk or protective factors associated with seropositivity for this coronavirus. A feline population of 215 cats was analysed for AB group system blood phenotypes and antibodies against the nucleocapsid (N-protein) SARS-CoV-2 antigen using a double antigen ELISA. SARS-CoV-2 seropositive samples were confirmed using a surrogate virus neutralization test (sVNT). Origin (stray colony/shelter/owned cat), breed (DSH/non DSH), gender (male/female), reproductive status (neutered/intact), age class (kitten/young adult/mature adult/senior), retroviruses status (seropositive/seronegative), and blood phenotype (A, B, and AB) were evaluated as protective or risk factors for SARS-CoV-2 seropositivity. Seropositivity for antibodies against the SARS-CoV-2 N-protein was recorded in eight cats, but only four of these tested positive with sVNT. Of these four SARS-CoV-2 seropositive cats, three were blood phenotype A and one was phenotype AB. Young adult age (1-6 years), FeLV seropositivity and blood type AB were significantly associated with SARS-CoV-2 seropositivity according to a univariate analysis, but only blood type AB (p = 0.0344, OR = 15.4, 95%CI: 1.22-194.39) and FeLV seropositivity (p = 0.0444, OR = 13.2, 95%CI: 1.06-163.63) were significant associated risk factors according to a logistic regression. Blood phenotype AB might be associated with seropositivity for SARS-CoV-2 antibodies. This could be due, as in people, to the protective effect of naturally occurring alloantibodies to blood type antigens which are lacking in type AB cats. The results of this pilot study should be considered very preliminary, and we suggest the need for further research to assess this potential relationship.