Experimental intravenous, intratracheal, and intranasal inoculation of swine with SARS-CoV-2

Authors: Buckley, Alexandra; Falkenberg, Shollie; LAVERACK, MELISSA - Cornell University; MARTINS, MATHIAS - Cornell University; Palmer, Mitchell; DIEL, DIEGO - Cornell University; Lager, Kelly

Submitted to: American Association of Swine Veterinarians Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 9/23/2020
Publication Date: 2/18/2020
Citation: Buckley, A.C., Falkenberg, S.M., Laverack, M., Martins, M., Palmer, M.V., Diel, D., Lager, K.M. 2020. Experimental intravenous, intratracheal, and intranasal inoculation of swine with SARS-CoV-2 [abstract]. American Association of Swine Veterinarians Annual Meeting. p. 35-37.

Interpretive Summary:

Technical Abstract: Introduction Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is novel coronavirus that causes disease (COVID-19) in humans, and is hypothesized it has a zoonotic origin. Since swine and other livestock species are susceptible to other coronaviruses, research has been initiated to determine the susceptibility of livestock species to SARS-CoV-2 and if livestock can play a role in spread of the virus. Multiple groups have reported that swine are not susceptible to SARS-CoV-2 via intranasal inoculation; therefore, two different routes of inoculation (intravenous and intratracheal) were evaluated to determine if swine were susceptible to SARS-CoV-2. Materials and Methods Twenty four 3-week-old pigs were purchased from a commercial swine herd and transported to the National Animal Disease Center in Ames, IA. Control pigs were housed in ABSL-2, while challenged pigs and their contacts were housed in ABSL-3AG space. Three challenge routes were performed: intravenous (IV, n=4), intratracheal (IT, n=4) and intranasal (IN, n=4). Sham cell culture lysate challenge was administered to control pigs (n=2/route) with 2 control pigs untreated. Finally, one contact pig was added to each challenge group and the control room on 2 days post inoculation (dpi). Virus was isolated from a Malayan tiger that developed respiratory signs after infection with SARS-CoV-2 (TGR/NY/20). IV pigs received 2 mL, while both IT and IN groups received 5 mL of 6.8 x 106 TCID50/ml virus solution. Temperatures were recorded daily through the use of a microchip. Nasal-oral swabs, rectal swabs, and group oral fluids were collected on 0-7, 10, 12, 14, 18 and 21 dpi. Serum and whole blood were obtained at 0, 3, 7, 14, and 21 dpi. Samples were tested by PCR for the presence of virus and serum was utilized in a virus neutralization assay to test for neutralizing antibodies. At 21 dpi animals were euthanized and tissues were collected for PCR testing and histology. Results Immediately after IV challenge, pigs that received either virus or sham cell culture lysate began to vomit, but quickly recovered. No pigs in this study demonstrated any signs of clinical disease such as coughing, increased respiration, diarrhea or lethargy. In addition, temperatures recorded daily did not demonstrate any evidence of fever. At necropsy, there was no gross pathology visible in the pigs. PCR results, virus neutralization titers, and histology are pending. China and Germany have reported that all samples collected were negative after challenge, though Canada did report one PCR positive lymph node in SARS-CoV-2 challenged pigs. Conclusion Currently, there is no evidence that swine are susceptible to infection with SARS-CoV-2 via multiple inoculation routes, thus swine do not appear to be a reservoir and contribute to the epidemiology and spread of SARS-CoV-2 in the human population.