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1、1062AJVR, Vol 61, No. 9, September 2000 B ovine coronavirus (BCV) was first recognized as a cause of potentially fatal diarrhea of neonatal calves in 1972.1Additional investigations found this large, enveloped, single-stranded RNA virus in outbreaks of calf diarrhea2-4and winter dysentery of adult d
2、airy cat- tle5,6 as well as in calves with pneumonia.4,7-9 In 1996, investigators10isolated BCV from 38 of 100 cattle involved in outbreaks of respiratory tract disease at feedlots in Kansas and Arizona. That finding has prompted concern about the possible role BCV may play in the bovine respiratory
3、 disease complex (BRDC) of feedlot cattle. Considering the roles of multiple viruses in BRDC, it seems likely that BCV, with its tropism for the respi- ratory tract and association with pneumonia in calves, also could contribute to the pathogenesis of BRDC. Although evidence of BCV infections in fee
4、dlot cattle is available, it is still unclear the role it may play in BRDC, because we found that the virus also could be isolated from apparently healthy cattle.a To better define the role of BCV in BRDC, we surveyed 837 mixed-breed cattle entering 4 feedlots to describe shed- ding patterns of BCV
5、from the respiratory tract and rates of exposure. Information was collected on treat- ment rates for cattle with respiratory tract disease, pul- monary lesions at slaughter, and average daily gain to enable us to identify associations of BCV shedding and seroconversion with these outcomes. Materials
6、 and Methods Study populationFrom spring 1996 through fall 1997, 837 cattle (9 groups) that were entering 4 feedlots were surveyed for BCV in the nasal cavity. All cattle were between 4 and 7 months old and were predominantly mixed-breed calves. Samples were collected from clinically normal cattle a
7、nd those with signs of respiratory tract disease. Cattle at 3 feedlots in Ohio (Jackson, Lucasville, Wooster) and 1 in Texas (Amarillo) were used, as described elsewhere.11All cat- tle were vaccinated at arrival at their respective feedlots, using multivalent vaccines against agents including bovine
8、 herpesvirus-1 (BHV-1), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), and parainfluen- za-3 (PI-3) virus. Information was collected on treatment for cattle with respiratory tract disease and average daily gain. Cattle were treated in accordance with criteria establis
9、hed for each feedlot regarding identification of sick cattle and treat- ment protocol. Although the definition of cattle with respira- tory tract disease varied slightly between feedlots, it general- Received Jun 17, 1999. Accepted Oct 5, 1999. From the Food Animal Health Research Program (Lathrop,
10、Saif) and the Department of Animal Science (Loerch), Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, Wooster, OH 44691-4096; the Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, OH 43210 (Lathrop, Wittum, Bingham, Saif); the Dep
11、artment of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849 (Brock); the Division of Agriculture, West Texas A and the Texas A Thomas E. Wittum, PhD; Kenny V. Brock, DVM, PhD; Steven C. Loerch, PhD; Louis J. Perino, DVM, PhD; Howard R. Bingham, DVM, PhD; F . Ted McCo
12、llum, PhD; Linda J. Saif, PhD ObjectiveTo determine the association between respiratory tract infection with bovine coronavirus (BCV), treatment for respiratory tract disease, pul- monary lesions at slaughter, and average daily gain in cattle in feedlots. Animals837 calves in feedlots in Ohio and Te
13、xas. ProcedureNasal swab specimens were obtained from cattle at arrival in a feedlot (day 0) and at various times during the initial 28 days after arrival. Specimens were tested for BCV, using an antigen- capture ELISA. Serum samples were obtained at arrival and again 28 days after arrival and teste
14、d for antibodies to BCV, using an antibody-detection ELISA. Information was collected regarding treatment for cattle with respiratory tract disease and average daily gain during the feeding period. Pulmonary lesions were evaluated at slaughter. ResultsCattle shedding BCV from the nasal cavity and de
15、veloping an antibody response against BCV were 1.6 times more likely to require treatment for respiratory tract disease than cattle that did not shed the virus or develop an immune response against BCV. Additionally, cattle that shed BCV from the nasal cavity were 2.2 times more likely to have pulmo
16、nary lesions at slaughter than cattle that did not shed the virus. The BCV shedding or seroconversion status did not affect average daily gain. Conclusions and Clinical RelevanceBovine corona- virus infects feedlot cattle and is associated with an increased risk for cattle developing respiratory tract disease and pulmonary lesions. Development of appropriate control measures could help reduce the incidence of respiratory tract disease. (Am J Vet Res 2000;61:10621066) 20864r.qxd 10/21/2005 11:23
