RESEARCH SARS ORIGINS Susceptibility of Pigs and Chickens to SARS Coronavirus Hana M. Weingartl,* John Copps,* Michael A. Drebot,* Peter Marszal,* Greg Smith,* Jason Gren,* Maya Andonova,* John Pasick,* Paul Kitching,* and Markus Czub* An outbreak of severe acute respiratory syndrome (SARS) in humans, associated with a new coronavirus, was reported in Southeast Asia, Europe, and North America in early 2003. To address speculations that the virus originated in domesticated animals, or that domestic species were susceptible to the virus, we inoculated 6- week-old pigs and chickens intravenously, intranasally, ocularly, and orally with 106 PFU of SARS-associated coro- navirus (SARS-CoV). Clinical signs did not develop in any animal, nor were gross pathologic changes evident on postmortem examinations. Attempts at virus isolation were unsuccessful; however, viral RNA was detected by reverse transcriptase-polymerase chain reaction in blood of both species during the first week after inoculation, and in chick- en organs at 2 weeks after inoculation. Virus-neutralizing antibodies developed in the pigs. Our results indicate that these animals do not play a role as amplifying hosts for SARS-CoV. A(SARS) in humans, associated with a new coron- n outbreak of severe acute respiratory syndrome avirus (SARS-CoV), has been reported in Southeast Asia, Europe, and North America (1–3). According to the World Health Organization, SARS affected more than 8,200 peo- ple worldwide and killed more than 700. The sequence analysis of SARS-CoV suggests that it is substantially dis- tinct from all other known coronaviruses (1,2). Based on the nucleotide sequence, the virus is speculated to have evolved and been maintained in an animal host. However, no conclusive data have been presented to date on a possi- ble reservoir for this virus. Our study aimed to address the role of domestic animals in the outbreak, both from the public health perspective (as a potential source of virus for human infections) and the animal health perspective. A potential susceptibility of domestic species to SARS-CoV would have major implications on the management of live- stock operations worldwide. We have experimentally inoculated chickens and swine. Both species are natural hosts for a number of *Canadian Science Centre for Human and Animal Health, Winnipeg, Manitoba, Canada viruses from the same family as SARS-CoV (Coronaviridae). The infectious bronchitis virus of chick- ens, although distinct, groups genetically most closely with SARS-CoV (1,2). Swine can host several coron- aviruses (hemagglutinating encephalomyelitis virus, trans- missible gastroenteritis virus [TGEV], and porcine respira- tory coronavirus [PRCV]). In addition, continuous cultures of porcine turbinate cells (PT-K75) and primary chicken embryo epithelial kidney cells supported SARS-CoV repli- cation. Material and Methods Animals Six 4-week-old crossbred pigs were kept for 2 weeks to acclimatize before being inoculated. The pigs, obtained from a high health status herd (Sunnyside Colony LTD, Sunnyside, Manitoba), had preexisting antibodies against PRCV, likely of maternal origin (4), which decreased dur- ing the experiment, as determined by competitive enzyme- linked immunosorbent assay performed by the Veterinary Services Branch of Manitoba Agriculture and Food. Six-week-old, nonvaccinated, specific-pathogen-free chickens (White Leghorn), obtained from ADRI Nepean (Nepean, Ontario) were kept for 3 days to acclimatize before inoculation. They were housed in chicken isolators inside a biosafety level 4 (BSL4) animal cubicle. Animal housing and all animal manipulations were approved by the Animal Care Committee of the Canadian Science Centre for Human and Animal Health and met the Canadian Council on Animal Care guidelines. Virus SARS-CoV was plaque purified from a human isolate (Tor 3) on Vero E6 cells by using the plaquing method we describe in the SARS-CoV antibody detection section. Virus stock for animal inoculation was prepared and titrat- ed on Vero V76 cells. Virus replication in Vero E6, Vero V76, and PT-K75 cells was compared by employing the following plaque assay: an aliquot of each virus dilution was added in duplicate onto cell monolayers in 12-well Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 10, No. 2, February 2004 179