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PubMed1997

Molecular epidemiology of recent outbreaks of swine vesicular disease: two genetically and antigenically distinct variants in Europe, 1987-94.

Viruses from the recent epidemic of swine vesicular disease (SVD) in Europe have been isolated and characterized by antigenic and genetic methods to examine the likely epidemiological origins of the disease. Antigenic analysis was performed on 77 SVD viruses (SVDV) isolated in Europe between 1966 and 1994 using two panels of monoclonal antibodies (MAb) in a trapping ELISA. Genetic analysis of 33 of the SVD viruses by reverse transcription-polymerase chain-reaction (RT-PCR) amplification and nucleotide sequencing of the ID (VP1) coding region was also performed. Comparison of the nucleotide sequences with each other and with three other previously published SVDV sequences revealed four distinct groups which correlated exactly with the results of the pattern of reactivity with MAbs. The first group consisted solely of the earliest SVD virus isolated (ITL/1/66) while the second group comprised viruses present in Europe and Japan between 1972 and 1981. The third group consisted of viruses isolated from outbreaks of SVD in Italy between December 1988 and June 1992. Viruses isolated between 1987 and 1994 from Romania, the Netherlands, Italy and Spain formed a fourth group. The genetic and antigenic similarity of the most recent virus isolates from Western Europe to a virus isolated in Romania 5 years previously suggests that the possible origin of the recent epidemic of swine vesicular disease in Western Europe was in Eastern Europe.

Animals↗
PubMed1975

[Swine vesicular disease: pathological study (author's transl)].

Seventy-eight pigs inoculated with swine vesicular disease virus are autopsied at reaction times staged from day I to day 44. Two viral strains of different pathogenicity are studied. Non pathognomonic histological lesions of this disease are identical to those observed in foot and mouth disease. This confirms the relationship of the two viruses.

Animals↗
PubMed2000

Epidemiological investigation of the influence of environmental risk factors on respiratory diseases in swine--a literature review.

The influence of environmental and management factors on respiratory diseases in pigs is reviewed from an epidemiological point of view. The suitability of methods for the investigation of risk factors is discussed including aspects of study design, case definition, exposure assessment and data analysis. The results of published studies suggest a causal web of factor interaction, the analysis of which provides considerable challenges for current epidemiological techniques. New approaches to the problem should be further explored in the future in order to provide reliable advice to decision makers.

Animals↗
PubMed1998

Validation of a monoclonal antibody-based ELISA to detect antibodies directed against swine vesicular disease virus.

A simple, rapid and sensitive competitive monoclonal antibody-based ELISA for the detection of antibodies directed against swine vesicular disease virus (SVDV) was developed. The ELISA was validated using field sera originating from SVDV-infected and non-infected Dutch pig herds, reference sera obtained from the Community Reference Laboratory for Swine Vesicular Disease at the Institute for Animal Health, Pirbright Laboratory, UK, and sera from animals infected experimentally. When testing 4277 sera originating from non-infected Dutch pig herds and collected as part of the national screening program, this ELISA had only 0.6% false positive results, whereas approximately 2% of false positive results were obtained with a conventional blocking ELISA used until recently. A sensitivity relative to the virus neutralisation test of > 97% was achieved when testing sera collected from Dutch pig farms where an outbreak of SVDV had occurred. All international reference sera scored consistently correct. Sera collected sequentially from pigs experimentally infected with SVDV isolates representing all currently recognized antigenic groups, were scored positive slightly earlier by the ELISA compared to the virus neutralisation test. This monoclonal antibody-based competitive ELISA for SVDV antibodies designated the Ceditest ELISA for SVDV-Ab, is as sensitive but more specific than the ELISA used until recently. Because sera are tested at a single dilution (1:5), incubations are carried out at room temperature and test results are available within 3 h, this ELISA is simple, easy to automate and therefore very suitable for screening large numbers of serum samples.

Animals↗
PubMed1999

Porcine reproductive and respiratory syndrome virus comparison: divergent evolution on two continents.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a recently described arterivirus responsible for disease in swine worldwide. Comparative sequence analysis of 3'-terminal structural genes of the single-stranded RNA viral genome revealed the presence of two genotypic classes of PRRSV, represented by the prototype North American and European strains, VR-2332 and Lelystad virus (LV), respectively. To better understand the evolution and pathogenicity of PRRSV, we obtained the 12,066-base 5'-terminal nucleotide sequence of VR-2332, encoding the viral replication activities, and compared it to those of LV and other arteriviruses. VR-2332 and LV differ markedly in the 5' leader and sections of the open reading frame (ORF) 1a region. The ORF 1b sequence was nearly colinear but varied in similarity of proteins encoded in identified regions. Furthermore, molecular and biochemical analysis of subgenomic mRNA (sgmRNA) processing revealed extensive variation in the number of sgmRNAs which may be generated during infection and in the lengths of noncoding sequence between leader-body junctions and the translation-initiating codon AUG. In addition, VR-2332 and LV select different leader-body junction sites from a pool of similar candidate sites to produce sgmRNA 7, encoding the viral nucleocapsid protein. The presence of substantial variations across the entire genome and in sgmRNA processing indicates that PRRSV has evolved independently on separate continents. The near-simultaneous global emergence of a new swine disease caused by divergently evolved viruses suggests that changes in swine husbandry and management may have contributed to the emergence of PRRS.

5' Untranslated Regions↗
PubMed1995

Pathogenesis of swine vesicular disease after exposure of pigs to an infected environment.

The pathogenesis of swine vesicular disease (SVD) has been studied following a natural route of infection. In two experiments groups of ten and eight pigs respectively were introduced into a stable contaminated with SVD virus. At various intervals after stable exposure, pigs were killed and the amount of virus was determined in serum, vesicles (if present), spleen, kidney, and in seven lymph glands representing various parts of the body. One day after the pigs were introduced into the stable, five out of eight pigs were viraemic and virus could be isolated from various tissues. At 2 d after introduction, three out of four pigs killed had vesicular lesions on the feet. The tonsils of all pigs killed between 1 to 7 d after introduction into the stable were virologically positive. Four days after introduction 50% of the pigs were serologically positive and at 7 d all pigs had developed an antibody response. This study shows that contact with a SVD virus contaminated environment can be equally as infectious as injection, or direct contact with SVD infected pigs, causing a rapid spread of the disease. Because the tonsil was shown to be highly efficient in trapping and growing circulating virus, we recommend that in addition to serological examination, virus isolation from pig tonsils should be used to study the epidemiology of SVD on farms where the infection is present.

Animals↗
PubMed1983

Plaque morphology and pathogenicity for newborn mice of swine vesicular disease virus. I. Wild strains and their clones.

The population of wild swine vesicular disease virus (SVDV) strains was found non-homogeneous as manifested by varying plaque size and different pathogenicity of the clones obtained. The clones derived from large plaques (5-9 mm)--dominating among wild strains--were more virulent for newborn mice than those obtained from smaller plaques (1-2 mm). To evaluate the pathogenicity of wild SVDV strains the dose index was calculated; the clones were compared by dose index and theoretical pathogenicity index, respectively.

Animals↗
PubMed2005

Evaluation of the therapeutic activity of tulathromycin against swine respiratory disease on farms in Europe.

The clinical efficacy of tulathromycin in the treatment of natural outbreaks of swine respiratory disease (SRD) was evaluated at five European sites. Pigs (1 to 6 months of age) exhibiting clinical signs of SRD were treated intramuscularly with tulathromycin (n = 247) at 2.5 mg/kg on day 0 versus either tiamulin (n = 102) at 15 mg/kg on days 0, 1, and 2 (Germany, the Netherlands, and the United Kingdom) or florfenicol (n = 20) at 15 mg/kg on days 0 and 2 (France). Actinobacillus pleuropneumoniae, Pasteurella multocida, and Mycoplasma hyopneumoniae infections were the most frequently diagnosed pathogens. For both tulathromycin-treated animals and those treated with tiamulin or florfenicol, there were significant (P = .0001) reductions in mean rectal temperature and the severity of abnormal clinical signs on days 2 and 10 compared with day 0. There were no significant differences (P > .05) between treatments in average daily weight gain. Tulathromycin was found to be safe and highly effective in the treatment of natural outbreaks of SRD.

Animals↗
PubMed1977

Characterization of three antigenic particles of swine vesicular disease virus.

Three distinct particles were isolated from cell culture harvests of swine vesicular disease virus (SVDV) by sucrose and CsCl gradient centrifugation. Virions (148S), RNA-free empty capsids (81S), and a third particle (49S) also free of RNA showed immune reactivity with SVDV antiserum. The 81S and 49S particles had polypeptides typical of naturally occurring empty capsids. Injection of purified antigens into guinea pigs produced antisera which distinguished empty capsids from virions on immunodiffusion; the 49S antigen appeared similar to virions. Antisera produced to freshly prepared virus antigen grown in brains of baby mice distinguished SVDV from the serologically related Coxsackie B-5 virus but did not distinguish the individual S particle antigens. Partly purified virus preparations degraded to empty capsids when incubated in guinea pig serum. The possible origin of empty capsids and 49S particles and their relationship to antigenicity of virus preparations are discussed.

Animals↗
PubMed1989

The complete nucleotide sequence of swine vesicular disease virus.

The complete nucleotide sequence of the genome of the enterovirus swine vesicular disease virus (SVDV; H/3 '76) isolated from a healthy pig has been determined using molecular cloning and DNA sequencing techniques. The RNA genome was 7400 nucleotides long, excluding the poly(A) tract, and appeared to encode a single polyprotein of 2185 amino acids. The predicted amino acid sequence of the polyprotein showed close homology (around 90%) to that of the previously sequenced coxsackieviruses B1, B3 and B4, and also showed homology (around 60%) to that of poliovirus. This homology allows us to predict the possible cleavage sites of the polyprotein and to identify other features of structural and functional significance, which seem to be important to the biological integrity of the virus. A detailed analysis of homology between SVDV and coxsackieviruses shows that non-structural proteins are highly conserved whereas the structural proteins are less well conserved. The 5' and 3' non-coding regions are also conserved, although there are several divergent nucleotide stretches. These stretches may differentiate SVDV from coxsackieviruses.

Amino Acid Sequence↗
PubMed1995

Differential diagnosis and genetic analysis of the antigenically related swine vesicular disease virus and coxsackie viruses.

Monoclonal antibodies directed against an isolate of swine vesicular disease virus (SVDV), characterized by virus neutralization tests and competition assays, were used to compare SVDV isolates and isolates of the antigenically related Coxsackie viruses by ELISA. SVDV-specific reaction patterns and one specific for Coxsackie viruses were observed. This provided a method for distinguishing between these enteroviruses. In addition, RT-PCRs were undertaken with Coxsackie virus and SVDV genomes. Different product patterns were obtained which correlated with the genetic differences revealed by nucleotide sequence determination. RT-PCR distinguished between SVDV and Coxsackie viruses by pattern differences. Further SVDV-specific PCRs were carried out with clinical samples. Viral genomes were detected with a sensitivity equivalent to that of virus isolation in cell culture. Sequencing of the Coxsackie virus-derived 2A-coding PCR products resulted in a not previously described sequence of a B5 isolate and in SVDV-specific sequence of two Coxsackie virus A16 isolates. The differences of the isolates by ELISA and PCR reactivity, as well as the nucleotide sequence differences are consistent with the quasispecies concept of RNA viruses.

Animals↗
PubMed2002

Mapping of linear epitopes on the capsid proteins of swine vesicular disease virus using monoclonal antibodies.

The antigenic linear map of swine vesicular disease virus (SVDV) has been studied using a repertoire of monoclonal antibodies (mAbs) raised against a recombinant SVDV polyprotein, P1. Peptide-scanning analyses, cross-reactivity studies with homologous and heterologous viruses and predicted location on a computer-generated three-dimensional model of the capsid proteins have allowed the identification of five main linear sites. Two sites, the N terminus of VP3 and amino acids 51-60 on VP1, correspond to internal areas, conserved not only between SVDV isolates but also in the related enterovirus coxsackievirus B5. In contrast, three other regions, amino acids 142-161 of VP2, 61-70 of VP3 and the C terminus of VP1, are exposed on the external face of the capsid and subjected to antigenic variation, even among different SVDV isolates. Further minor sites that were antigenically conserved were identified on VP4. In contrast with conformational sites described previously, none of the linear epitopes identified in this work is involved in neutralization of virus infectivity and post-infection swine sera did not inhibit the binding of mAbs with the relevant epitopes. Both of these observations suggest that linear epitopes are poorly immunogenic in pigs. The characterization of linear sites has contributed to a better understanding of the antigenic structure of SVDV and mAbs used to this purpose may provide a useful tool for the improvement of diagnostic methods, such as antigen detection systems, and analyses of the antigenic profile of SVDV isolates.

Amino Acid Sequence↗
PubMed1979

Molecular approach to the epidemiology of swine vesicular disease: correlation of variation in the virus structural polypeptides with serological properties.

Variation has been observed in the structural polypeptides of swine vesicular disease viruses isolated from the United Kingdom and Hong Kong. Despite the limited number of isolates examined, several distinct polypeptide patterns were obtained when the virus structural proteins were examined by polyacrylamide gel electrophoresis. Isolates from outbreaks in the United Kingdom which were known to be connected gave the same polypeptide pattern, whereas viruses with different polypeptide patterns could not be traced to a common source. The different polypeptide patterns were obtained consistently and were not altered by passage of the virus in tissue culture. In general, isolates with identical polypeptide patterns could not be distinguished by neutralization or antibody blocking tests or by competition radioimmunoassays. However, isolates with different polypeptide patterns could be differentiated by antibody blocking tests or radioimmunoassay. The correlation between the serological tests and the polyacrylamide gel electrophoresis analyses illustrates the value of analyzing structural polypeptides in the epidemiological study of swine vesicular disease.

Animals↗
PubMed1974

Experimental edema disease of swine (E. coli enterotoxemia). I. Dectection and preparation of an active principle.

Freeze-thaw lysates prepared from strains of Escherichia coli belonging to serogroups O138, O139, and O141 contained a principle (edema disease principle) which induced edema disease in swine. All freeze-thaw lysates contained endotoxic activity that tended to obscure the edema disease syndrome and methods were developed to reduce such activity. Freeze-thaw lysates prepared from E. coli O139 induced the most characteristic edema disease syndrome. Partially purified edema disease principle prepared from O139 freeze-thaw lysates by sequential precipitation with ammonium sulphate and streptomycin sulphate had increased specific activity with markedly reduced endotoxic activity. This material was insoluble at acidic pH but readily soluble at alkaline pH. The effective molecular weight of edema disease principle, based on retention and filtration properties of diaflo membranes, appeared to be greater than 50,000 and less than 100,000. The biological activity of edema disease principle was thermolabile. Sodium deoxycholate treatment of edema disease principle further reduced endotoxic activity. A thermolabile, ammonium sulphate precipitable material was prepared from E. coli O139 that induced a predictable syndrome which resembled edema disease clinically and pathologically following intravenous inoculation in pigs.

Ammonium Sulfate↗
PubMed1995

Identification of the location of antigenic sites of swine vesicular disease virus with neutralization-resistant mutants.

Neutralization sites on swine vesicular disease virus (SVDV) have been identified by sequence analysis of neutralization-resistant mutants. Eight neutralizing monoclonal antibodies (MAbs) were produced and neutralization-resistant mutants were selected with the MAbs. Resistance of the mutants to neutralization was shown using the stab-neutralization method, and the results indicated the presence of five neutralization sites on the virus. The location of each site was identified from amino acid changes resulting from nucleotide substitutions in the mutants, and designated site 1 (residues 87 and 88 of VP1), 2a (residue 163 of VP2), 2b (residue 154 of VP2), 3a (residue 272 and 275 of VP1, 60 of VP3) and 3b (residues 70 and 233 of VP2, 73 and 76 of VP3). The locations of the amino acids substitutions at each site formed a cluster on a computer-simulated three-dimensional model of SVDV and were exposed to the surface of the virion.

Amino Acids↗
PubMed1995

Development of two novel monoclonal antibody-based ELISAs for the detection of antibodies and the identification of swine isotypes against swine vesicular disease virus.

Two novel formats of ELISA for the detection of antibodies against swine vesicular disease (SVD) virus were developed. One of the tests described is a monoclonal antibody-based competitive ELISA (MAC-ELISA). In this test, specific antibodies in serum are detected due to their ability to compete with a neutralizing monoclonal antibody (MAb). The second is an indirect trapping ELISA which employs isotype-specific MAbs to detect swine IgG or IgM specific for SVD virus. The diagnostic sensitivity and specificity of the MAC-ELISA was studied on 5671 field sera of known origin, enabling the cut-off level to be defined. Using the MAC-ELISA, 100% of sera from infected pigs were found positive, whereas only 0.45% of negative sera gave a false-positive result. A positive correlation between MAC-ELISA and virus neutralizing titres was recorded for pig sera collected sequentially after experimental infections. The results from the isotype-specific ELISA revealed the dynamics of the antibody response to SVD virus in pigs. The first antibodies were detectable as early as 3 days after experimental infection. Up to the 10th day, demonstrable antibodies were exclusively of the IgM class. IgG developed later, between 11 and 14 days postinfection and remained at a plateaux level throughout the whole investigation period. The two tests satisfy different diagnostic requirements: the MAC-ELISA is useful as a screening test, the isotype-specific ELISA has potential application for the determination of stage of infection. Both tests benefit from the use of MAbs in terms of specificity and standardization and have advantages over the virus neutralization test.

Animals↗