Abstract.A case of an enteric coronavirus infection in a 6-week-old dromedary calf is described. The animal had diarrhea for 5 days and died despite symptomatic treatment. Numerous viral particles, approximately 140 nm in diameter, with club-like projections were detected in the feces by electron microscopy. These characteristics were consistent with a coronavirus. Immunohistochemical reactivity with 2 antigenic group II coronavirus-specific antibodies confirmed the presence of viral antigen in colonic epithelial cells. The death of the animal was attributed to a neutrophilic and emphysematous colitis that likely was caused by an infection with a Clostridium sp.A 6-week-old female dromedary (Camelus dromedarius) calf with a history of acute diarrhea died 5 days after the initial symptoms. According to the owner, the calf was born in Missouri on a pasture that was also inhabited by zebras. The camel nursed from its mother for 1 week after birth. At 1 week of age, the calf was separated from its mother and shipped to a farm in Wisconsin. Upon arrival, the calf was contained indoors and initially fed approximately 1 liter of warm calf milk replacer a containing oxytetracycline and neomycin 4 times per day. The amount of milk replacer was gradually increased to approximately 2 liters per feeding. Clover grass hay was available at all times. The calf had contact with miniature horses, zebras, and reindeers that were kept in the same barn in different stalls. The calf was healthy for approximately 4 weeks. Its weight was approximately 75 kg. Five days before death, the calf developed watery diarrhea after initially being bloated. The owner administered penicillin (approximately 20,000 units/kg) intramuscularly. The calf was presented to the referring veterinarian for the first time approximately 1 day after the initial signs were noted by the owner. The animal appeared to be mildly dehydrated. The calf was treated by the veterinarian with butorphanol, b dipyrone, c and flunixin meglumine d intravenously and received electrolytes per os because it was still drinking. At the second visit 2 days later, the rectal temperature was approximately 35 C (reference range 7 : 36-40 C). The hematocrit was slightly elevated (37.5%; reference range 13 : 26-31%). The calf was tachycardic (60 heart beats/ minute; reference range 7 : 40-50 beats/minute). The white blood cell count was 16,000 leukocytes/ml (reference range 13 : 13,000-24,000) with neutrophilia (83%; reference range 13 : 53-74%). The anti-inflammatory and antibiotic treatment was continued but the calf died and was submitted to the Department of Veterinary Diagnostic Medicine, University of Minnesota, St. Paul, Minnesota, for postmortem examination. Tissue samples, including small and large intestine, lung, brain, liver, kidney, spleen, heart, intestinal lymph node, and adrenal gland, were fixed in 10% buffered formalin and embedded in paraffin. Sections cut at 4 m were stained with hematoxylin and eosin (HE). Additional sections of the intestine were stained with a mod...
Bovine coronavirus (BCV) is 1 of the important causes of scours in young calves.1 Although the role of BCV in respiratory tract infections has not been clearly defined, there is increasing evidence that it causes upper respiratory tract infection in addition to the intestinal disease. 5,6 Focal involvement of lungs was recently reported in 2 of 16 calves experimentally infected with BCV, 5 but the sequence of events including clinical signs has not been clearly described for pneumotropic BCV.The present report describes a consistent, diffuse lung involvement in calves experimentally infected with a field isolate of BCV. The details of the experimental design have been described.2 Briefly, newborn, colostrum-deprived, unvaccinated calves were infected orally at 5 days of age with either a virulent pneumoenteric isolate of BCV (Minnesota isolate, calves 2, 6, and 7) or with an attenuated strain of BCV (Mebus strain, calves 1 and 9). The virus suspension was fed slowly to the calves with a 20-ml syringe. Although direct inoculation of the virus into the nasal cavity was unlikely, it was not possible to control the carryover of virus to the nasal cavity via insertion of the tongue into the nostril. Four calves (calves 3, 4, 5, and 8), housed in separate rooms were included as uninfected controls. One of the uninfected controls (calf 3) developed a natural infection with BCV. Nasal cells were collected by inserting cotton swabs a into the anterior nasal cavity of the calves. The swabs were rotated gently to dislodge the cells of the nasal cavity. Sufficient number of cells were collected without difficulty. The swabs were placed in Hanks' balanced salt solution (HBSS) and immediately transported to the laboratory where they were vortexed for 1 minute to separate nasal cells from the swab and the mucus. The swab was removed from the tube and the resulting suspension was centrifuged at 650 x g for 5 minutes. The pellet (approx. 0.05 ml packed cells) was mixed with equal volume of HBSS and vortexed again. The cell suspension was placed on 8-well slides with 30 µ1/well and allowed to dry at room temperature.The slides were washed with phosphate-buffered saline (PBS), pH 7.2, dried, and then fixed in acetone for 10 minutes. After drying again, the wells were covered with a drop of FITC-labeled bovine anti-BCV conjugate b and incubated in a humid chamber for 1 hour. The conjugate was found to be specific for bovine coronavirus and did not react with uninfected Madin-Darby bovine kidney cells or with uninfected tissues from control calves (gut and lungs). The slides were washed with PBS (pH 8.5) and counterstained with Evan's blue.The calves were kept under strict quarantine and were Received for publication June 13, 1990. observed closely for clinical signs of the disease at least twice daily. In the present report, only the signs and pathology associated with the pneumoenteric strain of BCV are presented. Calf 2 inoculated with the virulent pneumoenteric strain developed diarrhea within 1 day after infection but did no...
Bovine peripheral blood lymphocytes (PBL's) from 3 cows and 1 steer infected with bovine leukemia virus (BLV) were separated by fractionation through nylon wool columns into nylon-adherent and nonadherent cell populations. Nylon-adherent cells were enriched in B-lymphocytes, as determined by the presence of surface membrane immunoglobulins (slg), whereas nylon-nonadherent cells or "non-B-lymphocytes" contained few slg-bearing cells. PBL's and separated B- and non-B-lymphocyte populations were assayed for the presence of BLV by the induction of syncytia in bovine embryonic spleen cells. PBL's and B-lymphocyte populations both produced many syncytia, whereas non-B-lymphocytes yielded few or no syncytia. The specificity of syncytia formation by anti-BLV serum. PBL's from 2 control animals were negative for syncytia induction. This study presents further evidence that B-lymphocytes are the target cells for BLV infection.
Abstract. The effect of blind passage and centrifugation on the isolation of bovine coronavirus in human rectal tumor cells cultured in shell vials was investigated. A total of 68 fecal samples known to be positive for bovine coronavirus by transmission electron microscopic (TEM) examination were used. The samples were centrifuged onto human rectal tumor cell monolayers and incubated in the presence of trypsin. The growth of bovine coronavirus in infected cells was demonstrated by fluorescent antibody staining, and the extracellular virus was detected and confirmed by hemagglutination and hemagglutination-inhibition tests, respectively. Of the 68 TEM-positive samples, 51 (75%), 58 (85%), and 61 (90%) grew in shell vial cell cultures at first, second, and third passages, respectively. Of the 51 cultures positive on first passage, 19 were examined by TEM; 18 of these were positive for bovine coronavirus. The shell vial technique was also compared with direct detection of bovine coronavirus by staining cryostat sections of infected tissues in a direct fluorescent antibody assay. The results of direct fluorescent antibody assay were available for 54 of the 68 samples, of which 53 (98%) and 43 (80%) were positive by shell vial technique and direct fluorescent antibody assay, respectively. For identification of bovine coronavirus, shell vials using human rectal tumor cells in the presence of trypsin is more sensitive than direct fluorescent antibody assay but is relatively less sensitive than transmission electron microscopy.
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