Macromolecular permeability of the small intestine was tested in four 3-week-old gnotobiotic pigs inoculated with porcine rotavirus strain RV277 (group A). Pigs were administered 125I-labeled polyvinylpyrrolidone (molecular weight [mol wt], 40,000) orally 1 day before and 2 and 24 hours after virus inoculation, and blood samples were obtained every 6 hours. Eight hours after rotavirus inoculation, pigs had watery diarrhea. Increased permeation of 125I-labeled polyvinylpyrrolidone was not observed after clinical signs of infection had developed. Serum total protein and urea nitrogen concentrations increased slightly at the end of the study, probably as a consequence of dehydration. Differences in blood glucose concentration were not seen. At 48 hours after viral inoculation, macromolecular permeability was tested morphologically by injecting horseradish peroxidase (mol wt, 40,000) into the jejunal lumen just distally to the ligamentum colicoduodenale. After an incubation period of 20 minutes, small segments of jejunum were obtained for stereomicroscopic, histologic, and ultrastructural investigations. Moderate hyperregenerative villus atrophy was found. Ultrastructural changes of the villus epithelium were minor, and increased macromolecular permeation was not observed.

Hepatitis E virus (HEV), norovirus (NoV), and rotavirus (RV) are all hypothesized to infect humans zoonotically via exposure through swine and pork. Our study objectives were to estimate Canadian farm-level prevalence of HEV, NoV [specifically porcine enteric calicivirus (PEC)], and RV in finisher pigs, and to study risk factors for farm level viral detection. Farms were recruited using the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) and FoodNet Canada on-farm sampling platforms. Six pooled groups of fecal samples were collected from participating farms, and a questionnaire capturing farm management and biosecurity practices was completed. Samples were assayed using validated real-time polymerase chain reaction (RT-PCR). We modeled predictors for farm level viral RNA detection using logistic and exact logistic regression. Seventy-two herds were sampled: 51 CIPARS herds (15 sampled twice) and 21 FoodNet Canada herds (one sampled twice). Hepatitis E virus was detected in 30/88 farms [34.1% (95% CI 25.0%, 44.5%)]; PEC in 18 [20.5% (95% CI: 13.4%, 30.0%)], and RV in 6 farms [6.8% (95% CI: 3.2%, 14.1%)]. Farm-level prevalence of viruses varied with province and sampling platform. Requiring shower-in and providing boots for visitors were significant predictors (P < 0.05) in single fixed effect mixed logistic regression analysis for detection of HEV and PEC, respectively. In contrast, all RV positive farms provided boots and coveralls, and 5 of 6 farms required shower-in. We hypothesized that these biosecurity measures delayed the mean age of RV infection, resulting in an association with RV detection in finishers. Obtaining feeder pigs from multiple sources was consistently associated with greater odds of detecting each virus.

A virologic survey was conducted on calves with diarrhea associated with bovine rotavirus (BRV) on a closed dairy farm. The BRV was detected from 32 of 219 (14.6%) fecal specimens repeatedly collected from 56 calves born during the years 1992-1993, regardless of whether they had diarrhea. Most of the 32 strains were isolated from fecal specimens obtained from 2-to 6-week-old calves. After electrophoresis of doublestranded viral RNA from the 32 strains, genomic RNA migration patterns were similar to those of the predominant BRV strains isolated at the same farm during the years 1990-1991. All representative strains were identified as G serotype 6 (G6) and P type 5 (P5) by results of the virus-neutralization test and polymerase chain reaction procedure. Thus, BRV had no change in genomic RNA electropherotypes and serologic antigenicities in a closed dairy herd over a period of several years.

Observations were made on development of diarrhea in special-fed calves (n = 460) on 8 commercial facilities during 2 successive 16-week production cycles at weeks 0, 2, 4, 8, 12, and 16. A total of 23% were affected, with peak number of calves with diarrhea observed at week 0. Suspected enteropathogens were identified in 86% of these calves, most commonly cryptosporidia, coronavirus, and rotavirus. Identified potential zoonotic pathogens included Giardia and Salmonella spp and verotoxigenic Escherichia coli. Noncytopathic bovine viral diarrhea virus was isolated from 6 calves that had repeated bouts of illness. Only 22% of calves entering the veal facilities had adequate transfer of passive immunity. At week 0, serum IgG concentration in calves that subsequently died or had diarrhea was lower (P < 0.001) than that in healthy calves. All calves that died (n = 6) during the first 4 weeks of production had complete failure of transfer of passive immunity.

Fecal samples were collected from 450 neonatal calves, ranging from 1 to 30 days old, between May, 1988 and May, 1989 to estimate the prevalence of bovine group A rotavirus in a stratified random sample of Ohio dairy herds. Calves were from 47 dairy herds chosen to be representative of Ohio herds. Bovine group A rotavirus was detected in fecal samples by a cell culture immunofluorescence test (CCIF) and ELISA. Of 450 samples tested, 46 (10%) were positive by CCIF and 67 (15%) were positive by ELISA. The agreement beyond chance between the 2 assays was good (kappa = 0.65). The overall prevalence rate of rotavirus shedding was 16.4% (74/450). Forty-three percent (29/67) of the samples positive by ELISA were subgroup 1, none were subgroup 2, and the remaining 57% (38/67) could not be assigned to either subgroups 1 or 2. Thirty herds (62.5%) had at least 1 group A rotavirus-positive calf (mean number of samples per positive herd = 12.4), and 17 herds (37.5%) had no rotavirus-positive calves (mean number of samples per negative herd = 6.0). A live oral rotacoronavirus vaccine was used in neonatal calves of only 1 herd and 3 of 17 (17.6%) calves from this herd were positive for group A rotavirus. The percentage of the rotavirus-positive fecal samples from all calves (n = 450) when stratified by fecal consistency was as follows: 28.3% (13/46) had liquid feces; 25.6% (10/39) had semiliquid feces; 23.4% (22/94) had pasty feces; and 10.7% (29/271) had firm feces. Of the rotavirus-positive calves (n = 74), 17.6% (13/74) had liquid feces; 13.5% (10/74) had semiliquid feces; 29.7% (22/74) had pasty feces; and 39.2% (29/74) had firm feces. The average age of calves shedding rotavirus was 14 days (range, 1 to 30 days). Double-stranded (ds) RNA extracted from 36 samples positive by 1 or both tests was examined by polyacrylamide gel electrophoresis. All samples positive by this technique (30/36) had long dsRNA migration patterns, typical of group A rotaviruses, including samples from calves in the herd in which the oral vaccine was used. Moreover, the electrophoretic migration pattern of group A rotavirus dsRNA in these vaccinated calves differed from that of the rotavirus vaccine strain, suggesting the rotavirus strain circulating in this herd was not the vaccine strain. All samples negative by CCIF or ELISA that had volumes > 5 ml (n = 323) were also subjected to dsRNA extraction and polyacrylamide gel electrophoresis for detection of additional group A or nongroup A rotaviruses; none of them were positive by this technique.

Macromolecular permeability of the small intestine was tested in four 3-week-old gnotobiotic pigs inoculated with porcine rotavirus strain RV277 (group A). Pigs were administered 125I-labeled polyvinylpyrrolidone (molecular weight [mol wt], 40,000) orally 1 day before and 2 and 24 hours after virus inoculation, and blood samples were obtained every 6 hours. Eight hours after rotavirus inoculation, pigs had watery diarrhea. Increased permeation of 125I-labeled polyvinylpyrrolidone was not observed after clinical signs of infection had developed. Serum total protein and urea nitrogen concentrations increased slightly at the end of the study, probably as a consequence of dehydration. Differences in blood glucose concentration were not seen. At 48 hours after viral inoculation, macromolecular permeability was tested morphologically by injecting horseradish peroxidase (mol wt, 40,000) into the jejunal lumen just distally to the ligamentum colicoduodenale. After an incubation period of 20 minutes, small segments of jejunum were obtained for stereomicroscopic, histologic, and ultrastructural investigations. Moderate hyperregenerative villus atrophy was found. Ultrastructural changes of the villus epithelium were minor, and increased macromolecular permeation was not observed.

The virulence of 2 porcine group-A rotavirus isolates was compared. Forty hysterotomy-derived 3-day-old gnotobiotic pigs were inoculated orally with 2 ml of intestinal homogenate containing either the Ohio State University (OSU) or the South Dakota State University (SDSU) strain of porcine rotavirus or were inoculated with medium only. Clinical signs of disease, body weight, distribution of viral antigen, fecal excretion of virus, and histologic lesions (observed by light and scanning electron microscopy) were determined. Morphometric measurements of villi and crypts were made. In pigs inoculated with OSU or SDSU strains, diarrhea began at postinoculation hours (PIH) 19 to 48 and PIH 24 to 54, respectively. None of the virus-infected pigs died as a consequence of infection and all had similar clinical signs of disease, body weight changes and virus-shedding patterns, regardless of the strain of rotavirus with which they were infected. Microscopic findings in the small intestine of virus-infected pigs were similar, except that the SDSU strain caused more severe villus atrophy and villus fusion in the duodenum at PIH 72 and 168 than was associated with the OSU strain. Viral antigen in the small intestine of pigs infected with either virus was observed by use of immunofluorescence at PIH 24 and 72, but was seldom seen at PIH 168.

A porcine rotavirus isolate was titrated in neonatal colostrum-fed and colostrum-deprived pigs. The stock rotavirus suspension had a titer of 10 /ml and was in its fifteenth cell culture passage in MA-104 cells. Fourteen colostrum-fed pigs were orally inoculated with dilutions of the stock virus suspension ranging from undiluted to 10-5. These pigs did not develop notable clinical signs during the 7-day experimental trial and no pathologic changes were found in intestine, liver, lung, kidney, spleen, or brain. However, rotavirus was detected in feces of the colostrum-fed pigs, using virus isolation and electron microscopic techniques. Rotavirus was also isolated from lung, brain, or spleen of 4 of 12 of these pigs. Sixteen colostrum-deprived pigs were orally inoculated with dilutions of the stock virus suspension ranging from 10-1 to 10-8. Diarrhea developed in 10 of 12 pigs that were given up to the 10-6 dilution. Seven of these 12 pigs died because of the severity of diarrhea. Pigs that died of rotavirus-induced diarrhea had severe villus loss in the jejunum and ileum. Villi of the small intestine of colostrum-deprived pigs that survived the severe diarrhea were within normal limits at the end of the 7-day trial. The colostrum-deprived pigs that were inoculated with a dilution less than 10-6 and survived past 96 hours underwent seroconversion. Rotavirus was detected by virus isolation and electron microscopy in the feces of all colostrum-deprived pigs that survived beyond 18.5 hours after inoculation. Virus was isolated from lungs, brain, or spleen of 12 of 16 colostrum-deprived pigs.

The nonstructural protein 4 (NSP4) of rotavirus encoded by gene 10, plays an important role in rotavirus pathogenicity. In this study, NSP4 gene of avian rotavirus (AvRV-1, AvRV-2) was analyzed and expressed using baculovirus expression system. The sequence data indicated that the NSP4 gene of AvRV-1 and AvRV-2 were 727 bases in length, encoded one open reading frame of 169 amino acids beginning at base 41 and terminating at base 550, and had two glycosylation sites. Nucleotide sequences of NSP4 gene of AvRV-1 and AvRV-2 exhibited a high degree of homology (88.1±7.6%) with avian rotaviruses, namely Ty1, Ty3 and PO-13.

Objective-To compare experimentally induced concurrent infection with bovine viral diarrhea virus (BVDV) and bovine rotavirus (BRV) with infection of either virus alone in calves. Animals-Seventeen 1-day-old gnotobiotic calves. Procedure-Calves were allotted to 8 treatments as follows: group 1, mock-infected control calves (n = 2); group 2, inoculated with BVDV on day 1 (2); groups 3, 5, and 7, inoculated with BRV on days 1 (2), 4 (1), or 7 (2), respectively; and groups 4, 6, and 8, inoculated with BVDV on day 1 and with BRV on days 1 (2), 4 (2), or 7 (4), respectively. Concentrations of BVDV in serum and ileal tissues were measured, and BRV shedding in feces was determined. Histologic examination and immunohistochemical analysis were conducted to detect lesions and viral antigens. Results-Neonatal calves inoculated with BVDV alone or with BVDV on day 1 and BRV on day 7 developed villus atrophy and submucosal inflammation of the intestines. Concurrent BVDV and BRV infections acted synergistically in the intestinal tract, causing more severe enteric disease than infection with either virus alone. Severe lymphoid depletion was associated with BVDV infection in calves regardlesss of concurrent BRV infection. Conclusions and Clinical Relevance-Infection with BVDV played direct and indirect roles in enteritis in neonatal calves, causing villus atrophy in the duodenum and submucosal inflammation of the intestines. Also, BVDV potentiated effects of BRV. Concurrent infection with BVDV and BRV resulted in more severe enteric disease in neonatal calves than infection with BRV or BVDV alone.