Experimental Infection and Transmission of SARS-CoV-2 Delta and Omicron Variants among Beagle Dogs

Abstract

S ince COVID-19 was first reported in China in late 2019 and quickly became a worldwide pandemic, zoonotic aspects of SARS-CoV-2 have raised public health concerns (1). The first reported case of SARS-CoV-2 infection in a companion animal was in Hong Kong (2). Pet dogs living with patients affected by COVID-19 shed low levels of SARS-CoV-2 and show seroconversion without any clinical signs (2). Multiple cases of SARS-CoV-2 transmission from humans to dogs have since been reported in several countries (3). In experimental infection studies, dogs inoculated with SARS-CoV-2 wild-type strain manifested no clinical signs or seroconversion, shed low titers, or had undetectable viral RNA (4,5). As companion animals, dogs commonly share living spaces with humans; therefore, more studies are needed to elucidate the susceptibility of dogs to SARS-CoV-2 infection.SARS-CoV-2 variants Delta, in late 2020, and Omicron, in 2021, emerged and quickly spread worldwide. Those variants have been characterized by more efficient human-to-human transmission than the wild-type strain (6). In this study, we assessed susceptibility of beagle dogs to SARS-CoV-2 Delta and Omicron variants and transmissibility of SARS-CoV-2 variants from infected to naive dogs. The StudyWe obtained SARS-CoV-2 Omicron (NCCP 43408, BA.1. lineage) and Delta (NCCP 43390, B.1.617.2 lineage) variants from the National Culture Collection for Pathogens of South Korea. We passaged the viruses twice in Vero E6 cells and titrated the virus stocks on Vero E6 cells using a 50% tissue culture infectious dose (TCID 50 ) assay. This study was performed at the Animal Use Biosafety Level 3 facility of the Korea Zoonosis Research Institute. The Institutional Animal Care and Use Committee approved animal experiments (approval number JBNU 2022-033), and the Institutional Biosafety Committee of Jeonbuk National University approved experimental protocols requiring biosafety (approval no. JBNU2022-02-002).We purchased 9 male beagle dogs, all 9 months of age, from Orient Bio Inc. (http://www.orient.co.kr). We intranasally inoculated 2 dogs with 10 6.0 TCID 50 / mL SARS-CoV-2 Delta variant and 2 others with 10 6.0 TCID 50 /mL SARS-CoV-2 Omicron variant (infected dogs). Twenty-four hours after infection, we housed 2 virus-naive dogs (transmission dogs) each with the infected dogs in separate large animal isolators, 1 for Delta-infected dogs and 1 for Omicron-infected dogs (total 4 dogs in each isolator, 2 infected and 2 naive). We assigned 1 naive dog as the noninfected negative control and kept it separate from the other dogs. We recorded body temperature and weight, and collected blood, nasal swabs, and rectal swabs the day of and 2, 4, 6, 8, and 10 days after infection for the infected dogs or days after cohousing began for the

Multiplex One-Step RT-qPCR Assays for Simultaneous Detection of SARS-CoV-2 and Other Enteric Viruses of Dogs and Cats

“…Furthermore, Gaudreault et al [ 23 ] demonstrated viral RNA presence in the fecal samples of experimentally infected cats, highlighting the potential for viral dissemination via fecal shedding. Additionally, viral RNA was detected in rectal swabs collected from experimentally infected dogs [ 24 ]. These observations raise important questions regarding the infectivity of SARS-CoV-2 shed in feces, and the duration of viral excretion in companion animals.…”

Development and Validation of a Panel of One-Step Four-Plex qPCR/RT-qPCR Assays for Simultaneous Detection of SARS-CoV-2 and Other Pathogens Associated with Canine Infectious Respiratory Disease Complex

“…Nevertheless, cases of SARS-CoV-2 infection in dogs typically result in none to mild clinical manifestations and are not considered significant contributors to the spread of the virus [ 47 ]. While studies conducted on dogs experimentally infected with SARS-CoV-2 have revealed that they do not display signs of illness [ 44 , 48 , 49 ], transmission from experimentally infected dogs to naive dogs (sentinel controls) has been documented [ 50 ]. This raises concerns about the possible spillover between humans and dogs, requiring continuous surveillance to monitor SARS-CoV-2 infection in companion animals.…”

Neurologic Effects of SARS-CoV-2 Transmitted among Dogs

“…Wild-type SARS-CoV-2 infection in dogs can induce formation of neutralizing antibodies, and low viral titers in dogs demonstrate seroconversion ( 5 , 6 ). Mutant strains of SARS-CoV-2 in dogs cause histopathologic changes in lung tissues and increased expression of muscle damage markers in the blood ( 7 ). ACE2 in dogs can bind to the receptor-binding domain of SARS-CoV-2, implying the possibility of cross-species transmission between humans and dogs ( 8 ).…”