Characteristics of a coronavirus causing vomition and wasting in pigs

Some characteristics of a virus, isolated from the tonsils of 2 pigs with clinical signs of inappetence and vomition and designated VW572 were examined. It induced the formation of syncytia in primary pig kidney cell cultures, caused hemadsorption and hemagglutination using chicken, turkey, rat and mouse erythrocytes. In growth curve experiments, infectious virus was produced intracellularly starting at 6 hours after inoculation and was followed by rapid release of the virus from the infected cells. The virus contains ribonucleic acid, is ether sensitive and has a size between 100 and 220 nm. At 37° C, the infectivity titer decreased about 2 log(10)TCID(50) per 24 hours. The viral population was heterogeneous as indicated by the rate of inactivation by U.V. irradiation and acid pH. Some hemagglutinating activity was left after complete loss of infectivity by ether-, temperature- and U.V. treatment. The VW 572 isolate is antigenically related if not identical to isolates from Canada, U.S.A. and England which were classified as a porcine coronavirus. Oronasal and intracerebral inoculation of the VW572 isolate in colostrum deprived pigs resulted in clinical disease after an incubation period of 6 and 4 days, respectively. Signs were characterized by depression, vomition, loss of appetence with rapid weakness in young pigs and vomition with progressive wasting in older pigs. Virus was isolated from nasal and pharyngeal swabs, nasal mucosa, tonsils, lungs and hind brains but not from rectal swabs or other organs tested. Virus could not be isolated later than 8 days after inoculation. Hemagglutination inhibiting and neutralizing antibodies were detected in sera at 6 days and 9 days after inoculation, respectively.