Pigs susceptible to SARS-CoV-2, researchers discover
https://wwwnc.cdc.gov/eid/article/27/1/20-3399_article
In a study in Emerging Infectious Diseases late last week, Canadian and US researchers found that pigs are susceptible to SARS-CoV-2, the virus that causes COVID-19, highlighting the need for additional livestock assessment to determine the potential role of domestic animals in the pandemic.
Previous studies indicated that swine are not susceptible to SARS-CoV-2 infection, but they did not measure seroconversion (antibody production), the authors note.
They inoculated 19 8-week-old pigs (6 castrated males and 13 females) with an oronasal solution containing the SARS-CoV-2 virus, using a 10-fold higher infectious dose than that used in previous studies.
The researchers performed physical examinations and collected blood, rectal, oral, and nasal samples at the time of inoculation and every other day from day 3 until day 15. They evaluated samples for viral RNA using reverse-transcription polymerase chain reaction (RT-PCR) testing and tested blood serum for neutralizing antibodies. Necropsies and post-mortem sampling started at day 3 after inoculation and continued until day 29.
Starting at day 1, all of the pigs developed mild ocular discharge—accompanied by nasal secretion in some of the animals—which continued through day 3. Animal temperatures remained normal throughout the study, and none of the animals developed clinically observable respiratory distress, but one pig developed a mild cough lasting through day 4.
Among the 16 inoculated animals, 31.3% (5) displayed some level of exposure or an immune response to the virus. Only 1 pig—the animal that developed a mild cough—retained live virus, detected in a post-mortem sample of a lymph node. Two other animals had detectible RNA in a nasal wash sample, and two additional pigs had antibodies in blood serum. Among the five animals with potential infection, only low levels of viral RNA were detected, and no live viral shedding was identified.
Two control pigs were introduced to the infected pigs at day 10 to evaluate potential animal-to-animal transmission, but no viral infection occurred.
The authors conclude, "To date no SARS-CoV-2 cases among domestic livestock have been documented by natural infection; however, the results of this study support further investigations into the role that animals might play in the maintenance and spread of SARS-CoV-2."
