Susceptibility of domestic swine to experimental infection with SARS-CoV-2
Published 25 November 2020 | Update 14 June 2021
Pickering, B.S. et al. (2021) Susceptibility of domestic swine to experimental infection with SARS-CoV-2. Emerging Infectious Diseases, 27 (1), pp. 104-112. https://doi.org/10.3201/eid2701.203399.
This study reports on the experimental intranasal inoculation of 16, 8-week-old piglets with SARS-CoV-2. Two naïve pigs were placed in the room with the inoculated pigs at day 10 to serve as in-room transmission controls. One additional uninoculated pig was sampled and necropsied to serve as a “farm control” providing negative control tissues. A physical examination including collection of blood, multiple swabs (rectal, oral, and nasal), and nasal wash was performed at day zero and every other day beginning at three days post-inoculation (DPI) until day 15.
The authors report that during days 1-3 post inoculation (DPI), pigs developed a mild, bilateral ocular discharge and in some cases, this was accompanied by serous nasal secretion. Temperatures remained normal throughout the study and animals did not develop clinically observable respiratory distress, however one animal (Pig 20-06) presented mild depression at 1 DPI accompanied with a cough which was maintained through to 4 DPI.
Viral RNA could not be detected in swabs from any animals over the course of the study, although low levels of virus were detected in the nasal washes of two pigs and a weak antibody response was detected in two pigs. At necroscopy viral RNA, confirmed by PCR, was recovered from the submandibular lymph node from one pig.
The results of this study contradict previous reports indicating swine are not susceptible to SARS-CoV-2 infection but the authors note that in this study, a ten-fold higher viral dose was utilized for experimental infection compared to previous studies.