The role of pets in SARS-CoV-2 transmission: an exploratory analysis

doi:10.21203/rs.3.rs-1499014/v1

Purpose

There is evidence that humans can transmit SARS-CoV-2 to cats and dogs. However, there is no evidence that they can transmit it back to humans or play any role in SARS-CoV-2 transmission. Here, we present an exploratory analysis on that matter.

Methods

We conducted a case control study with participants with flu-like symptoms seeking care at a primary healthcare unit to be tested for COVID-19. They were asked if they owned pet cats and/or dogs in their residences, and this variable was evaluated as exposure.

Results

The odds ratio of “having dogs and/or cats in the residence” was 1.29 (95%CI 1.08–1.54) of “having only dogs and no cats” was 1.26 (1.05–1.52), and “no dogs and only cats” was 1.29 (0.95–1.75).

Conclusion

Having a cat/dog in the house can affect the risk of infection by SARS-CoV-2.

pet

dog

cat

SARS-CoV-2

COVID-19

The role of cats and dogs in the transmission and epidemiology of the Coronavirus disease 2019 (COVID-19) has been previously discussed [1–10]. Here, we present new data and further discuss that role.

Cats and dogs can be infected with the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) [3–7]. They may also develop COVID-19 with similar disease course and manifestation to humans, including respiratory symptoms and worse disease outcomes when comorbidities are present. Likewise, dogs may develop symptoms in the upper respiratory tract [5–7].

There is data strongly suggesting that humans can transmit SARS-CoV-2 to their cats and dogs [5–8], as well as evidence that experimentally infected cats can transmit the virus to non-infected ones [4, 8]. Nevertheless, there is no evidence supporting the hypothesis that cats and dogs could transmit the virus back to humans [8–10].

Some studies point out that cats may have a limited role in the COVID-19 epidemiology [8, 9]. Considering that cats and dogs can be infected with SARS-CoV-2 and that both may develop symptoms in a similar way that humans do [3–6], it would be reasonable to think about the possibility of these domestic animals transmitting the virus back to humans – and hence, being a risk factor for human infection. To help fill this knowledge gap, we evaluated whether cats and/or dogs living with humans may be a risk factor for SARS-CoV-2 infection in humans.

We conducted a case-control study with patients that sought medical care with COVID-19 symptoms. They were asked wether they owned pet cats and/or dogs to evaluate the exposition to SARS-CoV-2 and the associated risk of having a pet in their residences.

From 8th March to 31st November 2021, patients with flu-like/respiratory syndrome symptoms seeking medical care at a primary healthcare center in Cidade Estrutural (city nearby Brasilia, Distrito Federal, Brazil) were invited to participate in our study about COVID-19 incidence. All patients agreeing to participate signed consent instruments, were interviewed, and had nasopharyngeal samples collected using a swab for SARS-CoV-2 detection by RT-qPCR. The survey included questions about socio-demographic descriptors and the presence of pets in their residences.

RT-qPCR assays were performed with SARS-CoV-2 RNA isolated from nasopharyngeal swab samples. Nucleic acid extraction was conducted with the EXTRACTA 32 kit (MVXA-P016 FAST) in a Loccus automated extractor following manufacturer’s instructions. SARS-CoV-2 was detected by the RT-qPCR Allplex™ 2019-nCoV Assay (Seegene Inc.) for the amplification of genes E, RdRP and N, as well as an internal control gene, according to the manufacturer's protocol. RT-qPCR results were considered positive (SARS-CoV-2 RNA detected) when the internal control and at least two genes were amplified, negative (SARS-CoV-2 RNA not detected) when the internal control and none or only one gene was amplified, and inconclusive when the internal control did not amplify. Inconclusive results were repeated one time.

The inclusion criteria were: 1) answering the question of whether there were any pets in their residences, and if they did, specified which kind, and 2) having a positive or negative result in the SARS-Cov-2 detection test. Those who did not meet these criteria were excluded.

Sample characteristics were described with descriptive statistics. Odds Ratio (and its respective 95% confidence interval) of having a pet dog/cat in relation to being SARS-CoV-2-positive in RT-qPCR were then calculated.

All procedures were conducted in accordance with the ethical standards for research with human participants following the recommendations of the institutional and national research committees, and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the Research Ethics Committee of the Faculty of Medicine at University of Brasília (CEP-FM/UnB, CAAE 39892420.7.1001.5558; CAAE 40557020.6.3001.5553) and Fundação de Ensino e Pesquisa em Ciências da Saúde (FEPECS/SES/DF, CAAE 40557020.6.3001.5553).

A total of 2397 participants answered YES or NO to the question of whether there were any pets in their residences. Our 2397 participants were comprised by 62.5% (1497) female, 37.4% (897) male and 0.1% (3) did not answer this question; 2.5% (61) have no formal education, 29.3% (702) have completed elementary school, 50.8% (1217) have high school education, 16.4% (392) have a college degree, and 1% (25) did not answer this question. Regarding race, 78.8% (1888) self-declared as mixed-race or black; 14.8% (356) white; 3.1% (74) Asian; 1.4% (34) indigenous, and 1.9% (45) declared another race or did not answer the question. The mean age was 33.4 years old (median 31, Q1-Q3 23-42).

Out of those 2397 patients, 2322 (96.9%) had valid positive or negative results for SARS-CoV-2 detection by RT-qPCR, and 75 (3.1%) had inconclusive results and were therefore excluded from our analysis. Out of the remaining 2322 respondents, 739 (31.8%; 95% Confidence Interval [95%CI] 29.9-33.7) had positive RT-qPCR results.

Among those 2322 participants, 53.2% (1236) had a pet in their residence. Out of those, 61.3% (757/1236) had at least one dog and no cats in their residence; 16% (197/1236) had at least one cat and no dogs; 18% (223/1236) had cats and dogs in their residence; 2.4% (30/1236) had birds. A total of 2.3% (29/1236) did not specify which kind of pet they owned and were excluded from our study. Our final sample comprises 2293 participants who 1) answered whether they owned a pet; 2) specified the kind of pet they owned, and 3) received a valid positive or negative RT-qPCR result for SARS-CoV-2 infection.

We found that among the 2293 participants, 729 (31.8%; 95%CI 29.9-33.7) tested positive for SARS-CoV-2, and 1177 (51.3%) were exposed to the presence of dogs and/or cats in their residence.

The Odds Ratio (OR) for the presence of cats and/or dogs in human dwellings is shown in table 1.

The presented OR values (see Table 1) should be taken with some precaution. First, because previous reports indicate that pets are susceptible to transmission of SARS-CoV-2 from their owners [4–10], second, there is no scientific evidence to support that pets can transmit SARS-CoV-2 to humans [1–10]. However, our results could indicate that pets can contribute, somehow, to the SARS-CoV-2 transmission.

Therefore, there is a need for more research to understand SARS-CoV-2 epidemiology among humans and pet animals. A better understanding of the specific role of pets in the current COVID-19 epidemiology, using a One Health approach, might contribute to minimizing undefendable abandonment based on fear of transmission of SARS-Cov-2 [8–10]. Finally, the magnitude of the association between the presence of pets and the risk of humans having SARS-CoV-2 infection is small. Therefore, any intervention in this direction would have, if any, a very small impact on transmission. Summing it all up, pet owners with COVID-19 should not interact with their dogs or cats during the disease course to avoid transmitting the virus to their pets.

Author’s contributions

AIPT, RNB, CCG conceptualized and designed the study, analyzed all data, and drafted the initial manuscript. GASR, WMR, WNA, RH, and EFN performed critical revision of the manuscript. All authors read and approved the final manuscript.

Funding

This work was supported by the Ministério da Educação (MEC, http://portal.mec.gov.br/; grant number 23106.028855/2020-74) and Fundação de Amparo à Pesquisa do Distrito Federal (FAP-DF, http://www.fap.df.gov.br/; grant number 00193-00000495/2020-72).

Availability of data and materials

Data is available upon request from the corresponding author.

Code availability

Not applicable.

Declarations Conflict of interest

The authors declare no relevant financial or non-financial interests to disclose.

Ethics approval

The study was approved by the Research Ethics Committee of the Faculty of Medicine at University of Brasília (CEP-FM/UnB, CAAE 39892420.7.1001.5558; CAAE 40557020.6.3001.5553) and Fundação de Ensino e Pesquisa em Ciências da Saúde (FEPECS/SES/DF, CAAE 40557020.6.3001.5553).

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Table 1 – Number of participants with positive/negative test results for detection of SARS-CoV-2 and the Odds ratio values for human exposure to dog(s) and/or cat(s).

Exposures	Outcomes
	RT-qPCR positive	RT-qPCR negative	Total	Odds ratio (95%CI)
Having dogs and/or cats in the residence
Yes	406	771	1177	1.29 (1.08-1.54)
No	323	793	1116
Having dogs and no cats in the residence
Yes	267	490	757	1.26 (1.05-1.52)
No	462	1074	1536
Having cats and no dogs in the residence
Yes	73	124	197	1.29 (0.95-1.75)
No	656	1440	2096

The role of pets in SARS-CoV-2 transmission: an exploratory analysis

Status:

Version 1

Abstract

Purpose

Methods

Results

Conclusion

Introduction

Methods

Results

Discussion

Declarations

References

Tables

Status:

Version 1