Abstract.A recent epizootic of swine infertility and respiratory syndrome (SIRS) in a Minnesota swine herd was investigated. Examination of a sow, neonatal piglets, and stillborn fetuses obtained during the epizootic from the affected herd revealed interstitial pneumonitis, lymphomononuclear encephalitis, and lymphomononuclear myocarditis in the piglets and focal vasculitis in the brain of the sow. Fetuses did not have microscopic lesions. No cause for the infertility and respiratory syndrome was determined. Therefore, attempts were made to experimentally reproduce the disease. Eleven 3-day-old gnotobiotic piglets exposed intranasally to tissue homogenates of piglets from the epizootic became inappetent and febrile by 2-4 days postexposure and had interstitial pneumonitis and encephalitis similar to that seen in the field outbreak. After 2 blind passages in gnotobiotic piglets, tissue homogenates were cultured on continuous cell line CL2621, and a cytopathic virus (ATCC VR-2332), provisionally named SIRS virus, was isolated. Gnotobiotic piglets exposed intranasally to the SIRS virus developed clinical signs and microscopic lesions that were the same as those in piglets exposed to the tissue homogenates, and the virus was reisolated from their lungs. This is the first isolate of SIRS virus in the United States that fulfills Koch's postulates in producing the respiratory form of the disease in gnotobiotic piglets and the first report of isolation and propagation of the virus on a continuous cell line (CL2621). The virus is designated as American Type Culture Collection VR-2332.
This study reports the antigenic relatedness of isolates of Lelystad virus collected in the Netherlands, Germany, and the United States. The binding of antibodies directed against these isolates was tested in a set of field sera collected during outbreaks of porcine epidemic abortion and respiratory syndrome in Europe and outbreaks of swine infertility and respiratory syndrome (SIRS) in North America. Two sets of sera from pigs experimentally infected with Lelystad virus or SIRS virus were also tested. Although all 7 isolates reacted with anti-Lelystad virus sera, antigenic variation was considerable. The 4 European isolates resembled each other closely, but differed from the American isolates, and the 3 American isolates differed antigenically from each other. To reliably diagnose Lelystad virus infection, a common antigen must first be identified.
volves weaned pigs, and the clinical signs include inappe-Since approximately 1986, a syndrome of severe reproductive failure and respiratory disease has been afflicting swine herds and spreading throughout areas of the United tence, prolonged fever, coughing, rhinitis, and markedly reStates that have an intensive swine industry. 4 An outbreak of this disease costs approximately $236/sow, which is subduced growth rate. The pigs seem immunosuppressed because
Since 1980, the amount of evidence implicating a bovine coronavirus as the cause of winter dysentery has been increasing. 13 Japanese workers were the first to recover a coronavirus from the feces of a cow with "epizootic diarrhea"; 15 this discovery was followed by similar reports from Belgium 2 and the United States. 1 Because coronavirus-like particles and coronavirus antigen can be found in the feces of a high proportion of normal dairy cows in some herds during the winter stabling season, 3,4 the significance of these isolations has been interpreted with some reservation. Serologic studies revealed hemagglutination-inhibition seroconversion to reference strains of bovine coronavirus in 59% of affected Japanese cattle; 15 workers from Ohio reported 4-fold or greater rises in serum neutralization (SN) titers in 19 of 26 animals (73%); 14 and the British, using a latex agglutination inhibition test, found seroconversion in 3 of 5 affected cattle? We recently reported 63% seroconversion by an enzyme-linked immunosorbent assay (ELISA) method, in 35 sick animals from 8 herds with winter dysentery. 16 Additional evidence, and perhaps the most convincing, that a coronavirus is responsible for winter dysentery, is the demonstration by immunoperoxidase and electron microscopy methods of coronavirus in damaged colonic epithelial cells and mucosal macrophages of both spontaneous and experimentally induced cases. 18 In the Netherlands, however, there has been a serologic association of Breda virus infection with the occurrence of winter dysentery. 7,10 Sera from 149 cows from 19 farms were tested by a blocking ELISA method, and 4-fold or greater seroconversion was found in 7-60% of cattle tested from 10 of the farms; cattle from 9 farms showed no seroconversion. In view of questions raised about the respective roles of Breda virus and coronavirus, previously assembled and some newly acquired sera were tested (retested in the case of previously assembled sera) for the presence of antibodies to these 2 viruses. The procedure used to obtain and select the sera used in this study was described in the prior report. 16 Two serotypes of Breda virus are recognized; Breda virus serotype 1 (BRVl) represents the original isolate from Breda, Iowa, and serotype 2 (BRV2) comprises an isolate from Ohio and the second Iowa isolate. Thus far, Breda virus has not been successfully propagated in tissue culture; therefore all studies conducted with this agent employ density-gradientpurified virus particles obtained from an experimentally infected calf. 9 BRV2 is used for routine diagnostic tests because it is more stable than BRVl . 8 A direct blocking ELISA that has been previously described was used to detect antibody to Breda virus. 9,11 Serum neutralization anti-coronavirus antibody titers were determined by a method similar to that employed for rotaviruses. 6 Nebraska strain calfhood diarrhea coronavirus (No. 874 from the American type culture collection) was grown in Madin Darby bovine kidney cells in the presence of 0.1% pancreatin a...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.