Enteric disease in postweaned beef calves associated with Bo

Brief Communication

Enteric disease in postweaned beef calves associated with Bovine coronavirus clade 2

Robert W. Fulton,1 Heather R. Herd, Nicholas J. Sorensen, Anthony W. Confer, Jerry W. Ritchey, Julia F. Ridpath, Lurinda J. Burge

Journal of Veterinary Diagnostic Investigation2015, Vol. 27(1) 97 –101© 2014 The Author(s)Reprints and permissions:

http://doc.guandang.net/journalsPermissions.navDOI: 10.1177/http://doc.guandang.net

Abstract. Bovine coronavirus (BoCV; Betacoronavirus 1) infections are associated with varied clinical presentations including neonatal diarrhea, winter dysentery in dairy cattle, and respiratory disease in various ages of cattle. The current report presents information on BoCV infections associated with enteric disease of postweaned beef cattle in Oklahoma. In 3 separate accessions from a single herd, 1 in 2012 and 2 in 2013, calves were observed with bloody diarrhea. One calf in 2012 died and was necropsied, and 2 calves from this herd died in 2013 and were necropsied. A third calf from another herd died and was necropsied. The gross and histologic diagnosis was acute, hemorrhagic colitis in all 4 cattle. Colonic tissues from all 4 animals were positive by fluorescent antibody testing and/or immunohistochemical staining for BoCV antigen. Bovine coronavirus was isolated in human rectal tumor cells from swabs of colon surfaces of all animals. The genomic information from a region of the S envelope region revealed BoCV clade 2. Detection of BoCV clade 2 in beef cattle in Oklahoma is consistent with recovery of BoCV clade 2 from the respiratory tract of postweaned beef calves that had respiratory disease signs or were healthy. Further investigations on the ecology of BoCV in cattle are important, as BoCV may be an emerging disease beyond the initial descriptions. Challenge studies are needed to determine pathogenicity of these strains, and to determine if current BoCV vaccines are efficacious against the BoCV clade 2 strains.Key words: Beef cattle; Bovine coronavirus; enteric disease.

Bovine coronaviruses (BoCVs; Betacoronavirus 1) are enveloped, nonsegmented, positive-sense, single-stranded RNA viruses that are grouped as a species within the Coro-navirus genus of the Coronaviridae family.13 Bovine corona-viruses are found in the respiratory tract and intestinal tract of cattle,6,10 where they are shed in feces and nasal secretions and infect the lung.6,10 Bovine coronaviruses are associated with different syndromes in cattle: calf diarrhea, winter dys-entery in adult cattle, and respiratory infection in cattle of different age groups.8–10 These clinical forms have been the subject of reviews.1,8–11 Bovine coronaviruses are often found associated with bovine respiratory disease (BRD) in postweaned beef calves entering the stocker operations or feedlots.5 To date, BoCV control programs may include modified live virus (MLV) or killed vaccines.7 The MLV vaccines may be used in neonates to control enteric disease or used in pregnant cows, which may transfer BoCV antibod-ies in the colostrum or milk secretions, to control BoCV for the neonates after calving. There are no USDA-approved BoCV vaccines in the United States to control BRD.

In an Oklahoma study, BoCVs have been isolated from nasal secretions and lung washing (lavage) fluids in post-weaned beef calves in the feedlot.5 Bovine coronaviruses have been recovered from calves presented with BRD signs and from healthy calves, as well as from lung samples

collected at necropsy from fatal cases of BRD in feedlot cat-tle.3 The BoCV isolates recovered from stocker cattle in

Oklahoma were compared antigenically and genetically to previously isolated BoCV strains including those from neo-natal enteric disease, reference strains, and to the strain in current MLV BoCV licensed in the United States.4 Based on these comparisons, BoCV field isolates from Oklahoma stocker cattle have been described as BoCV clade 2, and neo-natal enteric disease isolates, reference strains and an MLV vaccine strain as BoCV clade 1.4 With the emergence of the new BoCV clades distinct from reference strains, previously reported neonatal enteric cases, and the MLV strain, attempts have been made to investigate BoCV in Oklahoma in both enteric disease cases as well as respiratory isolates. In the current study, BoCV clade 2 was recovered from 3 separate clinical cases in 2012 and 2013. Clinical presentation

From the Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK (Fulton, Herd, Sorensen, Confer, Ritchey,

Burge), and U.S. Department of Agriculture, Agriculture Research Service, National Animal Disease Center, Ames, IA (Ridpath).

Corresponding Author: Robert W. Fulton, Department of Veterinary Pathobiology, Room 250 McElroy Hall, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078. robert.fulton@okstate.edu

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sections, and culture for Salmonella spp. was negative. The

spleen was FAT negative for BVDV antigen and culture for Salmonella spp. was negative. Culture for Clostridia spp. was not requested, as the lesions were not indicative of clos-tridial disease. Fresh intestine was submitted to the research laboratory of an author (RW Fulton), and swabs were made of colon surface and frozen until tested for BoCV. The sam-ple was labeled as OK NF INT 1.

At postmortem examination of the 2 calves in case 2 (2013), both calves were in good body condition. Both car-casses were diffusely pale, and the blood of both calves was thin and watery. The colon and rectum of both calves was filled with a large amount of watery, dark red fluid admixed with numerous variably sized blood clots and a small amount of coarse feed material. The colonic and rectal mucosa was stained red, but contained no evidence of ulceration. Sec-tions of proximal gastrointestinal tract cont …… 此处隐藏：20740字，全部文档内容请下载后查看。喜欢就下载吧 ……