Objective-To inoculate white-tailed deer (Odocoileus virginianus) during the sixth or seventh week of gestation with bovine viral diarrhea virus (BVDV) and observe for signs of reproductive tract disease during a 182-day period. Animals-10 pregnant white-tailed deer (8 seronegative and 2 seropositive [control deer] for BVDV). Procedures-Deer were inoculated with 1 of 2 deer-derived BVDV strains (RO3-20663 or RO3-24272). Serum anti-BVDV antibody titers were determined prior to and 21 or 35 days after inoculation. Virus isolation (VI) procedures were performed on tissues from fetuses and does that died and on blood samples collected from live fawns. Ear notch specimens obtained from live fawns were assessed by use of BVDV antigen-capture ELISA (ACE). Results-Both RO3-20663-inoculated seropositive deer gave birth to apparently normal fawns. Among the RO3-24272-inoculated seronegative deer, 1 died, and 1 aborted and 1 resorbed their fetuses; among the RO3-20663-inoculated seronegative deer, 3 died, 1 aborted its fetus, and 1 gave birth to 2 fawns that were likely persistently infected. On the basis of VI and ACE results, those 2 fawns were positive for BVDV; both had no detectable neutralizing anti-BVDV antibodies in serum. Conclusions and Clinical Relevance-Reproductive tract disease that developed in pregnant white-tailed deer following BVDV inoculation was similar to that which develops in BVDV-exposed cattle. Methods developed for BVDV detection in cattle (VI, immunohistochemical evaluations, and ACE) can be applied in assessments of white-tailed deer. Fawns from does that had serum anti-BVDV antibodies prior to inoculation were protected against BVDV infection in utero.

Calves persistently infected (PI) with Bovine viral diarrhea virus (BVDV) represent an important source of infection for susceptible cattle. We evaluated vaccine efficacy using calves PI with noncytopathic BVDV2a for the challenge and compared tests to detect BVDV in acutely or transiently infected calves versus PI calves. Vaccination with 2 doses of modified live virus vaccine containing BVDV1a and BVDV2a protected the calves exposed to the PI calves: neither viremia nor nasal shedding occurred. An immunohistochemistry test on formalin-fixed ear notches and an antigen-capture enzyme-linked immunosorbent assay on fresh notches in phosphate-buffered saline did not detect BVDV antigen in any of the acutely or transiently infected calves, whereas both tests had positive results in all the PI calves.

Pseudorabies virus (PRV) nucleic acids in the trigeminal ganglia and tonsils of swine latently infected with the virus were analyzed. By use of DNA-polymerase chain reaction (PCR), 14 of 14 trigeminal ganglia and 12 of 14 tonsils were positive for PRV genomes. By use of RNA-PCR, RNA containing the large latency transcript splice junction were detected in 4 of 4 trigeminal ganglia and 4 of 5 tonsils. In general, results of both PCR procedures indicated that the amounts of PRV DNA and RNA per microgram of cellular nucleic acids were higher in trigeminal ganglia than in tonsils. Identification of peripheral tissues that harbor latent PRV is an important asset for PRV research. The presence of large latency transcript in tonsil tissues, in the absence of virus replication, is a critical characteristic, which indicates that the tonsil is a site of PRV latency. For diagnostic purposes, animals need not be euthanatized to obtain their nervous tissue to determine latency; instead, tonsil biopsy specimens could be obtained from live animals for analysis. For pathogenesis studies, multiple specimens obtained sequentially from the same animal would be available for examination for the duration of the experiment.

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.

A longitudinal survey of 820 cats in 73 households was conducted over a period of 6 years to establish the fate of pet cats that were seropositive after natural exposure to feline coronavirus (FCoV). In particular, their risk of developing feline infectious peritonitis (FIP) was determined. The seropositive cats were assigned to 1 of 3 groups: cats from households in which FIP had recently been diagnosed; cats from households in which FIP had not been diagnosed, but from which kittens had been relocated and subsequently died of FIP; and cats from households in which FIP had not been diagnosed. Cats in the first group were not at greater risk of developing FIP than were cats in the other 2 groups. Consequently, any household in which seropositive cats live must be considered a potential source of FCoV that can cause FIP. There was no evidence that the enhanced disease, which has been described after experimentally induced infection of seropositive cats, exists in nature. Thus, analysis of the survival of the seropositive cats over periods of up to 36 months indicated that their risk of developing FIP decreased with time, suggesting the development of immunity rather than increased susceptibility to disease. In addition, of 56 cats deemed to have been naturally reinfected because their anti-FCoV antibody titers decreased and subsequently increased, only 3 developed FIP.

Sequential histologic, immunologic, and virologic features of herpesvirus-induced keratitis were studied in 18 experimentally infected cats. Histologic changes were assessed by use of light microscopy, and the presence of viral antigen, B lymphocytes, and T lymphocytes was verified immunohistochemically. Flow cytometry was used to monitor changes in blood T lymphocytes (CD4 and CD8 homologues) and B lymphocytes. Cellular immunity was assessed by use of the lymphocyte proliferation assay. Development of stromal keratitis was preceded by prolonged absence of corneal epithelium, decreased numbers of circulating lymphocyte subsets, decreased mitogen responses, and acquisition of viral antigen by the corneal stroma. Return to normal of circulating lymphocyte numbers and function was temporally associated with the arrival of neutrophils and B and T lymphocytes in the corneal stroma. Sequelae to stromal inflammation were fibrosis and scarring. Findings suggest that suppression of local immune responses allows virus access to the corneal stroma, and that subsequent keratitis is mediated by an immune response to viral antigen.

The Rice strain of pseudorabies virus (PRV) was intranasally instilled in pigs that were seronegative to PRV. Cells were scraped or brushed from tonsillar surfaces biweekly until pigs were euthanatized at either 10 or 16 weeks after infection. The DNA extracted from tonsillar cells or parenchyma were subjected to polymerase chain reaction analysis, using either a single set of oligonucleotide primers or nested primers from the PRV gII glycoprotein gene. Pigs became seropositive to PRV by 3 weeks after infection. The virus was isolated from the trigeminal ganglia and tonsils of pigs that were euthanatized or died 1 to 2 weeks after infection, but not from pigs that were euthanatized 10 or 16 weeks after infection. The PRV gene products were consistently detected in trigeminal ganglia and tonsils of all pigs at 1, 10, and 16 weeks after infection, and sporadically in the nasal mucosa, lymph nodes, and lungs of pigs that were euthanatized or died during the first 2 weeks after infection. Cells collected biweekly from tonsillar surfaces were mostly nucleated, squamous epithelial cells with fewer lymphocytes and neutrophils. Polymerase chain reaction analysis of DNA extracted from these cells revealed PRV DNA in a large proportion of the samples when sufficient cells were collected to provide 1 microgram of extracted DNA for use in the reaction mixtures. A second group of pigs had PRV strain 4892 intranasally instilled. The virus was isolated from tonsillar swab specimens until 3 weeks after infection. Tonsillar brushing specimens were collected biweekly until 14 weeks after infection. Some brushing specimens contained all nucleated, squamous epithelial cells, whereas other specimens contained a mixture of epithelial cells and up to 15% neutrophils, lymphocytes, and small mononuclear cells. Results of polymerase chain reaction analysis of DNA extracted from tonsillar cells collected 5, 11, and 14 weeks after infection were consistently positive for PRV gene products. Intact cells collected from tonsillar surfaces were placed in polymerase chain reaction mixtures with nested oligonucleotide primers from the PRV gII glycoprotein gene and were subjected to multiple amplification cycles. Afterward, the specificity of the amplified PRV gene products was determined by hybridization procedures, using a virus-specific oligonucleotide probe. Most nucleated, squamous epithelial cells stained positive for PRV DNA, suggesting that these cells were the primary source of PRV gene products in tonsillar brushing specimens.

In a search of viral agents in pulmonary macrophages of horses with chronic pulmonary disease, equine herpesvirus 2 was found to be unique. In 8 of 9 horses with chronic pulmonary disease, antigens of equine herpesvirus 2 were detected by indirect immunofluorescence staining of scattered foamy macrophages immediately after harvesting by bronchoalveolar lavage and fractionation on metrizamide gradients. In a healthy horse, antigens were not found. After 1 week of cultivation of bronchoalveolar lavage cells from a second group of 9 horses with chronic pulmonary disease, viral antigens were detected in 90% of the adherent pulmonary macrophages. In 2 of 3 healthy horses, viral antigens also were found in 90% of the adherent pulmonary macrophages. Antigens of equine herpesvirus 1, equine herpesvirus 4, parainfluenza virus 3, or adenovirus were not detected. Antigens of the 5 investigated viruses also were not detected in lung tissue slices from a third group of 14 horses, 4 healthy; 7 with varying degrees of bronchiolitis, 2 of which also had chronic intestitial pneumonia; 2 with eosinophilic bronchitis; and 1 with pulmonary hemorrhage. The exclusive presence of equine herpesvirus 2 in pulmonary macrophages was confirmed qualitatively by isolation of infective virus by cocultivation. In a fourth group of 12 horses with chronic pulmonary disease, infective virus could be isolated from pulmonary macrophages of 3 horses and from mixed-blood leukocytes of 5 horses. Virus isolations from 2 healthy horses were not successful from pulmonary macrophages, whereas 1 isolation was obtained from mixed-blood leukocytes. Other viruses were not detected by cocultivation.

To evaluate economic effects and health and performance of the general cattle population after exposure to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) in a feedlot. 21,743 high-risk calves from the southeastern United States. PI status was determined by use of an antigen-capture ELISA (ACE) and confirmed by use of a second ACE, reverse transcriptase-PCR assay of sera, immunohistochemical analysis, and virus isolation from sera. Groups with various amounts of exposure to BVDV PI cattle were used. After being placed in the feedlot, identified PI cattle were removed from 1 section, but PI cattle remained in another section of the feedlot. Exposure groups for cattle lots arriving without PI animals were determined by spatial association to cattle lots, with PI animals remaining or removed from the lot. 15,348 cattle maintained their exposure group. Performance outcomes improved slightly among the 5 exposure groups as the risk for exposure to BVDV PI cattle decreased. Health outcomes had an association with exposure risk that depended on the exposure group. Comparing cattle lots with direct exposure with those without direct exposure revealed significant improvements in all performance outcomes and in first relapse percentage and mortality percentage in the health outcomes. Economic analysis revealed that fatalities accounted for losses of $5.26/animal and performance losses were $88.26/animal. This study provided evidence that exposure of the general population of feedlot cattle to BVDV PI animals resulted in substantial costs attributable to negative effects on performance and increased fatalities.

Pathogens causing significant respiratory disease in growing pigs include Porcine reproductive and respiratory syndrome virus, Porcine circovirus 2, swine influenza virus, porcine respiratory coronavirus, Mycoplasma hyopneumoniae, and Bordetella bronchiseptica. The objective of this research was to characterize the respiratory excretion of these pathogens by acutely infected pigs. Pigs were inoculated under experimental conditions with 1 pathogen. Samples were collected from the upper respiratory tract and exhaled air. All pathogens were detected in swabs of the upper respiratory tract, but only M. hyopneumoniae and B. bronchiseptica were detected in expired air from individually sampled, acutely infected pigs. These findings suggest either that the acutely infected pigs did not aerosolize the viruses or that the quantity of virus excreted was below the detection threshold of current sampling or assay systems, or both, at the individual-pig level.