Abstract
Since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the susceptibility of animals and their potential to act as reservoirs or intermediate hosts for the virus has been of significant interest. Pigs are susceptible to multiple coronaviruses and have been used as an animal model for other human infectious diseases. Research groups have experimentally challenged swine with human SARS-CoV-2 isolates with results suggesting limited to no viral replication. For this study, a SARS-CoV-2 isolate obtained from a tiger which is identical to human SARS-CoV-2 isolates detected in New York City and contains the D614G S mutation was utilized for inoculation. Pigs were challenged via intravenous, intratracheal, or intranasal routes of inoculation (n = 4/route). No pigs developed clinical signs, but at least one pig in each group had one or more PCR positive nasal/oral swabs or rectal swabs after inoculation. All pigs in the intravenous group developed a transient neutralizing antibody titer, but only three other challenged pigs developed titers greater than 1:8. No gross or histologic changes were observed in tissue samples collected at necropsy. In addition, no PCR positive samples were positive by virus isolation. Inoculated animals were unable to transmit virus to naïve contact animals. The data from this experiment as well as from other laboratories supports that swine are not likely to play a role in the epidemiology and spread of SARS-CoV-2.
Highlights
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in China at the end of 2019 and has subsequently spread and infected humans around the globe [1,2].Bats are likely the reservoir host for SARS-CoV-2 and bat coronaviruses showed sequence similarity to SARS-CoV-2 [3]
Most swine SARS-CoV-2 challenge studies have previously reported that pigs challenged intranasally, intratracheally, intramuscularly, and/or intravenously were not susceptible to infection with SARS-CoV-2 [17,19,20,21]; Canadian researchers reported that pigs challenged intranasally were susceptible to SARS-CoV-2 [22]
PCR positive nasal/oral swabs and rectal swabs and virus neutralization (VN) activity in some animals from all challenge groups, viral nucleic acid detection and antibody titers were not sustained and there was no evidence of replicating virus via virus isolation
Summary
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in China at the end of 2019 and has subsequently spread and infected humans around the globe [1,2].Bats are likely the reservoir host for SARS-CoV-2 and bat coronaviruses showed sequence similarity to SARS-CoV-2 [3]. Other zoonotic coronaviruses have been transferred to humans to through intermediate animal hosts, including masked palm civets for severe acute respiratory syndrome coronavirus (SARS-CoV) [4] and camels for Middle East respiratory syndrome coronavirus (MERS-CoV) [5]. Given the epidemiologic association of early reported cases of SARS-CoV-2 with a seafood and wildlife animal market in Wuhan, China in December 2019, identification of susceptible animal species that could serve as intermediate hosts or become reservoirs for the virus is a research priority [6]. A HKU2-related bat coronavirus associated with swine acute diarrhea syndrome coronavirus (SADS-CoV) was recently discovered in 2016 and caused fatal disease outbreaks in swine in China near the geographic origin of the SARS-CoV outbreak [9]
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