Canine Circovirus 1 (CaCV-1) and Canine Parvovirus 2 (CPV-2): Recurrent Dual Infections in a Papillon Breeding Colony.

Recurrent outbreaks of sudden death and bloody diarrhea were reported in March 2013 and February 2014 in a breeding colony of Papillon dogs. During the first outbreak, 1 adult dog and 2 eight-month-old puppies died. During the second outbreak, 2 ten-week-old puppies died. One puppy from the first outbreak and 2 puppies from the second outbreak were examined at necropsy. Histologically, all 3 puppies had severe segmental crypt necrosis of the small intestine and marked lymphoid follicle depletion in the spleen and Peyer's patches. Real-time (RT) polymerase chain reaction (PCR) demonstrated abundant canine parvovirus (CPV-2) DNA (Ct<15) in the affected small intestine, and immunohistochemistry detected large amounts of CPV-2 antigen in intestinal crypt epithelium and Kupffer cells but few positive macrophages in lymphoid organs. All puppies had marked sinusoidal histiocytosis and multifocal granulomatous inflammation in mesenteric lymph nodes and spleen, prompting additional RT-PCR testing for canine circovirus 1 (CaCV-1). Very high levels of CaCV-1 DNA (Ct<13) were detected in small intestine, lymph nodes, and spleen. In situ hybridization for CaCV-1 detected rare positive nuclei of regenerating crypt epithelium but abundant amounts of CaCV-1 nucleic acid in the cytoplasm and nuclei of histiocytes in all lymphoid tissues, including granulomatous inflammatory foci and hepatic Kupffer cells. Significant levels of CaCV-1 DNA were detected in blood and serum (Ct as low as 13) but not feces from 3 surviving dogs at 2 months or 1 year after the outbreak, respectively. We hypothesize that CPV-2 infection predisposed dogs to CaCV-1 infection and ultimately resulted in more severe clinical disease.

Beyond H&E: integration of nucleic acid-based analyses into diagnostic pathology.

Veterinary pathology of infectious, particularly viral, and neoplastic diseases has advanced significantly with the advent of newer molecular methodologies that can detect nucleic acid of infectious agents within microscopic lesions, differentiate neoplastic from nonneoplastic cells, or determine the suitability of a targeted therapy by detecting specific mutations in certain cancers. Polymerase chain reaction-based amplification of DNA or RNA and in situ hybridization are currently the most commonly used methods for nucleic acid detection. In contrast, the main methodology used for protein detection within microscopic lesions is immunohistochemistry. Other methods that allow for analysis of nucleic acids within a particular cell type or individual cells, such as laser capture microdissection, are also available in some laboratories. This review gives an overview of the factors that influence the accurate analysis of nucleic acids in formalin-fixed tissues, as well as of different approaches to detect such targets.

Distribution of eastern equine encephalomyelitis viral protein and nucleic acid within central nervous tissue lesions in white-tailed deer (Odocoileus virginianus).

An outbreak of eastern equine encephalomyelitis (EEE) occurred in Michigan free-ranging white-tailed deer (Odocoileus virginianus) during late summer and fall of 2005. Brain tissue from 7 deer with EEE, as confirmed by reverse transcriptase polymerase chain reaction, was studied. Detailed microscopic examination, indirect immunohistochemistry (IHC), and in situ hybridization (ISH) were used to characterize the lesions and distribution of the EEE virus within the brain. The main lesion in all 7 deer was a polioencephalomyelitis with leptomeningitis, which was more prominent within the cerebral cortex, thalamus, hypothalamus, and brainstem. In 3 deer, multifocal microhemorrhages surrounded smaller vessels with or without perivascular cuffing, although vasculitis was not observed. Neuronal necrosis, associated with perineuronal satellitosis and neutrophilic neuronophagia, was most prominent in the thalamus and the brainstem. Positive IHC labeling was mainly observed in the perikaryon, axons, and dendrites of necrotic and intact neurons and, to a much lesser degree, in glial cells, a few neutrophils in the thalamus and the brainstem, and occasionally the cerebral cortex of the 7 deer. There was minimal IHC-based labeling in the cerebellum and hippocampus. ISH labeling was exclusively observed in the cytoplasm of neurons, with a distribution similar to IHC-positive neurons. Neurons positive by IHC and ISH were most prominent in the thalamus and brainstem. The neuropathology of EEE in deer is compared with other species. Based on our findings, EEE has to be considered a differential diagnosis for neurologic disease and meningoencephalitis in white-tailed deer.

Polyomavirus-associated nephritis in 2 horses.

Polyomaviruses produce latent and asymptomatic infections in many species, but productive and lytic infections are rare. In immunocompromised humans, polyomaviruses can cause tubulointerstitial nephritis, demyelination, or meningoencephalitis in the central nervous system and interstitial pneumonia. This report describes 2 Standardbred horses with tubular necrosis and tubulointerstitial nephritis associated with productive equine polyomavirus infection that resembles BK polyomavirus nephropathy in immunocompromised humans.

Cutaneous lymphomas in European pet rabbits (Oryctolagus cuniculus).

Cutaneous lymphoma is a common skin neoplasm of pet rabbits in Europe but is rarely reported in pet rabbits in North America. These neoplasms have not been previously characterized, nor has the cause for the apparent predilection for cutaneous lymphoma in European pet rabbits compared with North American pet rabbits been investigated. In this retrospective study, the authors morphologically and immunohistochemically characterized 25 cutaneous lymphomas in European pet rabbits according to the World Health Organization classification. Tumors were classified as diffuse large B cell lymphomas, with 14 lymphomas exhibiting a centroblastic/centrocytic subtype and 11 tumors exhibiting a T cell-rich B cell subtype. To investigate a potential viral etiology of these lymphomas, 3 diffuse large B cell and 3 T cell-rich B cell lymphomas were evaluated by polymerase chain reaction for retroviral and herpesviral genes. Neither virus was detected. In contrast to other domestic animals, cutaneous lymphomas in European pet rabbits were highly pleomorphic and frequently contained multinucleated giant cells. Unexpectedly, the second most common subtype was T cell-rich B cell lymphoma, a subtype that is rare in species other than horses. Based on a limited number of samples, there was no support for a viral etiology that would explain the higher incidence of lymphoma in European pet rabbits compared with American pet rabbits. Further investigation into genetic and extrinsic factors associated with the development of these tumors is warranted.

Diagnostic algorithm to differentiate lymphoma from inflammation in feline small intestinal biopsy samples.

Differentiating between inflammatory bowel disease (IBD) and small intestinal lymphoma in cats is often difficult, especially when only endoscopic biopsy specimens are available for evaluation. However, a correct diagnosis is imperative for proper treatment and prognosis. A retrospective study was performed using surgical and endoscopic intestinal biopsy specimens from 63 cats with a history of chronic diarrhea or vomiting or weight loss. A diagnosis of lymphoma or inflammation was based on microscopic examination of hematoxylin and eosin (HE)-stained sections alone, HE-stained sections plus results of immunohistochemical labeling (IHC) for CD3e and CD79a, and HE staining, immunophenotyping, and polymerase chain reaction (PCR) results for B and/or T cell clonality. In addition, various histomorphologic parameters were evaluated for significant differences between lymphoma and IBD using Fisher's exact test. The sensitivity and specificity of each parameter in the diagnosis of lymphoma were also determined. Results of Bayesian statistical analysis demonstrated that combining histologic evaluation of small intestinal biopsy specimens with immunophenotyping and analysis of clonality of lymphoid infiltrates results in more accurate differentiation of neoplastic versus inflammatory lymphocytes. Important histologic features that differentiated intestinal lymphoma from IBD included lymphoid infiltration of the intestinal wall beyond the mucosa, epitheliotropism (especially intraepithelial nests and plaques), heterogeneity, and nuclear size of lymphocytes. Based on the results of this study, a stepwise diagnostic algorithm that first uses histologic assessment, followed by immunophenotyping and then PCR to determine clonality of the lymphocytes, was developed to more accurately differentiate between intestinal lymphoma and IBD.

Detection of group C rotavirus in juvenile ferrets (Mustela putorius furo) with diarrhea by reverse transcription polymerase chain reaction: sequencing and analysis of the complete coding region of the VP6 gene.

Nine juvenile ferrets (Mustela putorius furo) with a history of diarrhea were severely dehydrated and had distended abdomens and thin-walled small intestines that contained gas and fluid. Histologically, small intestines exhibited acute superficial atrophic enteritis. Transmission electron microscopy of the small intestine showed rotavirus-like particles within apical vacuoles. Reverse transcription polymerase chain reaction (RT-PCR) was negative for group A rotavirus. A group C rotavirus-specific RT-PCR assay was developed using consensus primers designed from the alignment of VP6 gene sequences of porcine, bovine, and human strains. A 182-bp product of the VP6 gene was sequenced and showed significant similarity to group C rotavirus VP6 sequences. This strain was designated "Ferret Rota C-MSU." The entire coding sequence of VP6 was determined and compared with other rotaviruses. Ferret Rota C-MSU virus was found to be most closely related to Shintoku group C rotavirus. This is the first definitive identification of a group C rotavirus in ferrets, based upon RT-PCR, sequencing, and genetic analysis.

Cholinergic reactivity of tracheal smooth muscle after infection with feline herpesvirus I.

Airway responsiveness was studied in cats 3 or 6 days after exposure to feline herpesvirus I. Control cats were sham inoculated with tissue culture media. Intrathoracic airway caliber was evaluated by pulmonary resistance (RL) and dynamic compliance (Cdyn). Trachealis shortening was quantitated with microfoil strain gauges, which measured the external diameter of tracheal ring 4. Airway smooth muscle contraction was produced using vagal stimulation and local infusion of acetylcholine. The diameter of tracheal ring 4 decreased with increasing frequency of vagal stimulation, and there was more constriction at 3 (PID3) than at 6 days postinfection (PID6) or in control cats. RL increased and Cdyn tended to decrease with increasing frequency of stimulation, but there was no difference between control and infected cats. Infected and control cats did not differ in their response to locally infused acetylcholine. Virus was consistently cultured from conjunctival, nasal, and oral mucous membranes, trachea, and main stem bronchi at PID3 but not from the trachea and main stem bronchi at PID6. Virus was never isolated distal to the main stem bronchi. Tracheal hyperresponsiveness to vagal stimulation correlates with the presence of virus at PID3 and is apparently presynaptic in origin.

Recent developments in latency and recombination of Aujeszky's disease (pseudorabies) virus.

Latency is a characteristic and fascinating part of the biology of alphaherpesvirinae, including ADV. Tissue explanation, blot hybridization, in situ hybridization and more recently PCR are the experimental methods used to demonstrate that latent infections consistently occur in ganglionic neurons and, at a lower level, in tonsillar and possibly other cells. In vivo reactivation of ADV, resulting in shedding of virulent ADV, has been demonstrated experimentally following administration of high doses of corticosteriods. To determine the influence of vaccination with currently used gene deleted vaccines on field virus latency load, it is essential to use quantitative latency detection methods. We have developed chemiluminescence-based quantitative PCR assays specific for gG and gE, and are currently using these to determine field virus latency loads in tissues of pigs vaccinated with one of several gene deleted vaccines. Recombination between ADV strains has been demonstrated both in vitro and in vivo and has raised concerns about the generation of gene deleted virulent ADV strains. Recent studies in a mouse model have shown that high concentrations of both strains have to be present at the same anatomical site for recombination to take place. This led to the conclusion that ongoing ADV eradication programs, based upon the use of gene deleted vaccines and differential serological testing, are not likely to be threatened by recombination between virulent ADV and gene deleted vaccine strains.

Polymerase chain reaction amplification of pseudorabies virus DNA from acutely and latently infected cells.

A characteristic of alphaherpesviruses, including pseudorabies virus (PRV), is that the acute phase of the disease is followed by lifelong latency. Latently infected animals are asymptomatic but can transmit reactivated virus. Corticosteroid administration, tissue explanation, blot- and in situ hybridizations have been used to demonstrate the presence of latent PRV infections. The use of blot hybridization as a convenient method for defining the incidence of PRV infections in swine herds has been hampered by the detection limit of this method. The objective of this study was to increase this sensitivity of blot hybridization by polymerase chain reaction (PCR) amplification of target sequences. Two sets of 20-mer primers were synthesized and used to amplify gX and gII glycoprotein gene sequences in two different strains of PRV. The specificity of the amplification was verified by Southern blot hybridization and restriction endonuclease analysis of the amplified fragments. Amplification of target sequences by PRC increased their detection limit by a factor of at least 10(5). Porcine ganglion samples, in which latency had been demonstrated by in vitro explanation, were analyzed by PCR together with positive and negative controls. Duplicate slot blot analyses of a portion of the amplified products were used to demonstrate latency in seven of eight samples. It was concluded that blot hybridization of PCR amplified DNA appears to be both a sensitive and convenient method for the detection of PRV induced latency.

Vaccine genotype and route of administration affect pseudorabies field virus latency load after challenge.

The influence of vaccine genotype and route of administration on the efficacy of pseudorabies virus (PRV) vaccines against virulent PRV challenge was evaluated in a controlled experiment using five genotypically distinct modified live vaccines (MLVs) for PRV. Several of these MLVs share deletions in specific genes, however, each has its deletion in a different locus within that gene. Pigs were vaccinated with each vaccine, either via the intramuscular or intranasal route, and subsequently challenged with a highly virulent PRV field strain. During a 2-week period following challenge with virulent PRV, each of the vaccine strains used in this study was evaluated for its effectiveness in the reduction of clinical signs, prevention of growth retardation and virulent virus shedding. One month after challenge, tissues were collected and analyzed for virulent PRV latency load by a recently developed method for the electrochemiluminescent quantitation of latent herpesvirus DNA in animal tissues after PCR amplification. It was determined that all vaccination protocols provided protection against clinical signs resulting from field virus challenge and reduced both field virus shedding and latency load after field virus challenge. Our results indicated that vaccine efficacy was significantly influenced by the modified live vaccine strain and route of administration. Compared to unvaccinated pigs, vaccination reduced field virus latency load in trigeminal ganglia, but significant differences were found between vaccines and routes of administration. We conclude that vaccine genotype plays a role in the effectiveness of PRV MLVs.

Application of antibody titers against bovine viral diarrhea virus (BVDV) as a measure to detect herds with cattle persistently infected with BVDV.

Based on the distribution of antibody titers against bovine viral diarrhea virus (BVDV) in 10 Michigan dairy herds, it was calculated that screening of 5 young stock for BVDV antibody titer could be used to distinguish herds with persistently infected (PI) animals from herds without such animals. The herds were selected to represent 3 different herd categories: A, herds without use of vaccination and without PI animals (5 herds); B, herds with use of killed vaccine but no PI animals (2 herds); C, herds with use of killed vaccine and presence of PI animals (3 herds). The animals were described as having high antibody titers (> or = 128) or low antibody titers (< or = 64). For animals from 9 to 18 months of age, the probability of obtaining at least 3 animals with high titers among a screening sample of 5 animals was calculated as < 0.001 for all herds in category A, < 0.01 for the 2 herds in category B, and > 0.99 for all herds in category C. Thus, among herds in this study, by categorizing 9-18-month-old animals as having high titers (> or = 128) or low titers (< or = 64), herds with PI cattle could be distinguished from other herds by testing only 5 animals.

Immunohistochemical diagnosis of eastern equine encephalomyelitis.

An immunohistochemical (IHC) assay was developed for the detection of eastern equine encephalomyelitis (EEE) virus antigen in formalin-fixed, paraffin-embedded tissues. All cases of EEE diagnosed at the Michigan State University Animal Health Diagnostic Laboratory from 1991 through 1994 were evaluated. The diagnosis was based on histopathologic examination of the brain and confirmatory virus, isolation. Sections of cerebrum from 26 equids and 5 birds were assessed by IHC. Histologically normal brain tissues from 2 horses and 1 pheasant and brain tissues from 2 cases of equine neurologic disease with diagnoses other than EEE served as negative controls. The IHC assay was based on standard streptavidin-biotin technology, using a commercially available kit and a monospecific polyclonal primary antibody preparation derived from murine ascitic fluid. Nineteen of 20 equids and all 5 birds positive by histopathology and virus isolation were positive for EEE virus antigen by IHC. Three equids with histologic lesions compatible with a diagnosis of EEE but negative by virus isolation also were negative for virus antigen by IHC. In 3 other equids, histopathology and IHC were positive for EEE, but virus isolation was not attempted because of contamination of the brain specimen. The IHC assay of formalin-fixed, paraffin-embedded brain tissues for EEE virus antigen is a rapid, effective test for confirming a histopathologic diagnosis of EEE, and assay results correlate well with virus isolation results.

Prevalence of cattle persistently infected with bovine viral diarrhea virus in 20 dairy herds in two counties in central Michigan and comparison of prevalence of antibody-positive cattle among herds with different infection and vaccination status.

All cattle in 20 dairy herds randomly selected from herds participating in the Dairy Herd Improvement Association program in 2 counties in central Michigan were tested for the presence of bovine viral diarrhea virus (BVDV). Virus-positive animals were retested to ascertain persistent infection with the virus. A total of 5,481 animals were tested for presence of BVDV. In 9 of the herds, all animals were also tested for virus neutralizing antibody titer. Based on infection and vaccination status, these 9 herds were divided into 3 different herd categories: A, 5 herds with currently no cattle persistently infected (PI) with BVDV and without any vaccination program against BVDV in recent years; B, 2 herds with no current PI cattle but using killed BVDV vaccines; and C, 2 herds with PI cattle. PI cattle were detected in 3 out of 20 herds (15%). A total of 7 of 5,481 animals (0.13%) were PI. The mean prevalences of antibody carriers in herd categories A, B, and C were 28.8%, 76.4% and 90.6%, respectively. For one herd in category A, antibody analyses indicated that mostly young stock was seropositive, suggested recent BVDV infection in a previously closed and naive herd. Cattle in category B herds were vaccinated with killed vaccine from the age of 15 months. These herds had several antibody negative animals among the younger cows, suggesting incomplete protection against BVDV infection. In the 3 herds in which PI animals were detected, all cattle had been vaccinated with killed vaccine. The antibody-positive animals had antibody titers that were significantly different both among herds and among herd categories.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental model of type II bovine viral diarrhea virus-induced thrombocytopenia in neonatal calves.

Thrombocytopenia has been associated with type II bovine viral diarrhea virus (BVDV) infection in immunocompetent cattle, but the mechanism is unknown. The purpose of the present study was to develop and characterize a model of type II BVDV-induced thrombocytopenia. Colostrum-deprived Holstein calves were obtained immediately after birth, given a BVDV-negative and BVDV antibody-negative plasma transfusion, housed in an isolation facility, and randomly assigned to either control (n = 4) or infected (n = 5) groups. Infected calves were inoculated by intranasal instillation on day 3 of age with 10(7) TCID50 of the prototype type II isolate, BVDV 890, whereas control calves were sham inoculated. Blood counts and virus isolations from serum, white blood cells, and platelets were performed daily until day 12 after infection, at which time all experimental calves were euthanatized, and pathologic, virologic, and immunohistochemical examinations were performed. On physical examination, the control calves remained normal, but the infected calves developed pyrexia and diarrhea characteristic of type II BVDV infection. The platelet count decreased in all infected calves, and a statistically significant difference in the platelet count between control and infected calves was observed on days 7-12 after infection. In addition, the mean platelet volume and white blood cell counts also decreased. Examination of the bone marrow from the infected calves revealed immunohistochemical staining for BVDV antigen in megakaryocytes and evidence of concurrent megakaryocyte necrosis and hyperplasia.

Prevalence of bovine herpesvirus-4 infection in cats in Central Michigan.

The gammaherpesvirus bovine herpesvirus-4 (BHV-4) has been isolated from a wide variety of animals, including lions and domestic cats. Although BHV-4 antibodies have been detected in normal cats and cats with urinary disorders, the epidemiology and pathogenic role of BHV-4 in cats is unknown. The purpose of this study was to determine the prevalence of BHV-4 antibodies and viral nucleic acid in a population of free-roaming cats. Plasma and peripheral blood leukocyte samples were collected from 52 male and 52 female free-roaming cats impounded at a regional animal control facility in Central Michigan. Plasma concentrations of BHV-4 antibodies were measured with an indirect fluorescent antibody test. Peripheral blood leukocyte DNA was isolated, and a 2-stage polymerase chain reaction with heminested primers delineating a conserved portion of the BHV-4 glycoprotein B gene homologue was used to amplify BHV-4-specific DNA sequences. BHV-4 antibodies were detected in 38 (73%) male and 23 (44%) female cats. Seropositive cats were significantly more likely to be male than female (odds ratio = 3.22; P = .007). Cell-associated viremia was detected in 17 (33%) male and 11 (21%) female cats. Of the 61 seropositive cats, 23 (38%) had a detectable viremia; only 5 (12%) seronegative cats had detectable viremia. Seropositive cats were significantly more likely to be viremic than seronegative cats (OR = 4.30: P = .009). Our results suggest that BHV-4 infection may be more widespread in certain cat populations than previously reported. Furthermore, many cats seropositive for BHV-4 antibodies have a concurrent cell-associated viremia.

Comparison of type I and type II bovine viral diarrhea virus infection in swine.

Some isolates of type II bovine viral diarrhea virus (BVDV) are capable of causing severe clinical disease in cattle. Bovine viral diarrhea virus infection has been reported in pigs, but the ability of these more virulent isolates of type II BVDV to induce severe clinical disease in pigs is unknown. It was our objective to compare clinical, virologic, and pathologic findings between type I and type II BVDV infection in pigs. Noninfected control and BVDV-infected 2-month-old pigs were used. A noncytopathic type I and a noncytopathic type II BVDV isolate were chosen for evaluation in feeder age swine based upon preliminary in vitro and in vivo experiments. A dose titration study was performed using 4 groups of 4 pigs for each viral isolate. The groups were inoculated intranasally with either sham (control), 10(3), 10(5), or 10(7) TCID50 of virus. The pigs were examined daily and clinical findings were recorded. Antemortem and postmortem samples were collected for virus isolation. Neither the type I nor type II BVDV isolates resulted in clinical signs of disease in pigs. Bovine viral diarrhea virus was isolated from antemortem and postmortem samples from groups of pigs receiving the 10(5) and the 10(7) TCID50 dose of the type I BVDV isolate. In contrast, BVDV was only isolated from postmortem samples in the group of pigs receiving the 10(7) TCID50 dose of the type II BVDV isolate. Type I BVDV was able to establish infection in pigs at lower doses by intranasal instillation than type II BVDV. Infection of pigs with a type II isolate of BVDV known to cause severe disease in calves did not result in clinically apparent disease in pigs.

Platelet aggregation responses and virus isolation from platelets in calves experimentally infected with type I or type II bovine viral diarrhea virus.

Altered platelet function has been reported in calves experimentally infected with type II bovine viral diarrhea virus (BVDV). The purpose of the present study was to further evaluate the ability of BVDV isolates to alter platelet function and to examine for the presence of a virus-platelet interaction during BVDV infection. Colostrum-deprived Holstein calves were obtained immediately after birth, housed in isolation, and assigned to 1 of 4 groups (1 control and 3 treatment groups). Control calves (n = 4) were sham inoculated, while calves in the infected groups (n = 4 for each group) were inoculated by intranasal instillation with 10(7) TCID50 of either BVDV 890 (type II), BVDV 7937 (type II), or BVDV TGAN (type I). Whole blood was collected prior to inoculation (day 0) and on days 4, 6, 8, 10, and 12 after inoculation for platelet function testing by optical aggregometry by using adenosine diphosphate and platelet activating factor. The maximum percentage aggregation and the slope of the aggregation curve decreased over time in BVDV-infected calves; however, statistically significant differences (Freidman repeated measures ANOVA on ranks, P < 0.05) were only observed in calves infected with the type II BVDV isolates. Bovine viral diarrhea virus was not isolated from control calves, but was isolated from all calves infected with both type II BVDV isolates from days 4 through 12 after inoculation. In calves infected with type I BVDV, virus was isolated from 1 of 4 calves on days 4 and 12 after inoculation and from all calves on days 6 and 8 after inoculation. Altered platelet function was observed in calves infected with both type II BVDV isolates, but was not observed in calves infected with type I BVDV. Altered platelet function may be important as a difference in virulence between type I and type II BVDV infection.

A seroepizootiologic study of five viruses in a swine-evaluation station.

This serologic study was done to gain information on the spread, maintenance, and effect upon performance of five porcine viruses. Blood samples were taken from two groups of 8- to 11-week-old pigs from a large number of Indiana swine herds in a performance-testing station 1 week after entry, 7 weeks after entry (one group only), and at slaughter. The sera were tested by indirect fluorescent antibody tests for antibodies to transmissible gastroenteritis virus (TGEV), swine influenza virus (SIV), hemagglutinating encephalomyelitis virus (HEV), porcine adenovirus (PAV), and pseudorabies virus (PRV). Seroconversions to TGEV, HEV, and PAV occurred in a group of pigs entered in May and slaughtered in August (group 1). In the group that was entered in October and slaughtered in January (group 2), pigs developed antibodies to SIV, HEV, and PAV, but not to TGEV. Only 1 of the 434 pigs tested had antibodies to PRV, and there were no seroconversions to this virus. The only statistically valid effect of infection on performance was found in group 1 pigs, which had seroconverted to TGEV during the first 7 weeks of their stay. These pigs gained 0.077 kg less per day than pigs that did not develop antibodies to TGEV during that period. The pattern of serologic reactions was indicative of a relatively slow spread of these viruses in the groups. We interpret this as supporting the concept that a relatively slow spread of these viruses through large groups of pigs kept under conditions that are less than optimum for virus spread may be an important means of their interepizootic survival.

Glycoprotein-specific immune responses in cats after exposure to feline herpesvirus-1.

To obtain synchronous infection, 10 cats were inoculated with feline herpesvirus-1 (FHV-1) on the oral, nasal, and conjunctival mucosa. Swab specimens of the nasal, conjunctival, and pharyngeal mucosa were obtained for virus isolation from each cat before inoculation and at 3-day intervals thereafter until postinoculation day 21. Recovery of virus and evidence of clinical signs were used to document FHV-1 infection. Serum was obtained from blood samples collected sequentially from each cat between day 0 and postinoculation day 90. Virus-neutralizing antibody titer was determined in all serum specimens. Immunoprecipitation with [35S]methionine- and [14C]glucosamine-labeled viral antigens, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was performed on each specimen. Three precipitation bands with approximate molecular weights of 105,000, 68,000, and 60,000 were separated from [14C]glucosamine- and [35S]methionine-labeled immunoprecipitates. The concurrent detection of virus-neutralizing antibody and glycoprotein-specific immunoprecipitins implied that in cats, the FHV-1 glycoproteins were important in the induction of virus-neutralizing antibodies to FHV-1.