Abstract
BackgroundThe aim of this study was to compare the tissue distribution and pathogenicity of three virulence variants of classical swine fever virus (CSFV) and to investigate the applicability of various conventional diagnostic procedures.Methods64 pigs were divided into three groups and infected with the highly virulent isolate ISS/60, the moderately virulent isolate Wingene'93 and the live attenuated vaccine strain Riems, respectively. Clinical signs, gross and histopathological changes were compared in relation to time elapsed post infection. Virus spread in various organs was followed by virus isolation, by immunohistochemistry, applying monoclonal antibodies in a two-step method and by in situ hybridisation using a digoxigenin-labelled riboprobe.ResultsThe tissue distribution data are discussed in details, analyzing the results of the various diagnostic approaches. The comparative studies revealed remarkable differences in the onset of clinical signs as well as in the development of the macro- and microscopical changes, and in the tissue distribution of CSFV in the three experimental groups.ConclusionThe present study demonstrates that in the case of highly and moderately virulent virus variants the virulence does not affect the pattern of the viral spread, however, it influences the outcome, the duration and the intensity of the disease. Immunohistochemistry has the advantage to allow the rapid detection and localisation of the virus, especially in cases of early infection, when clinical signs are still absent. Compared to virus isolation, the advantage of this method is that no cell culture facilities are required. Thus, immunohistochemistry provides simple and sensitive tools for the prompt detection of newly emerging variants of CSFV, including the viruses of very mild virulence.
Highlights
The aim of this study was to compare the tissue distribution and pathogenicity of three virulence variants of classical swine fever virus (CSFV) and to investigate the applicability of various conventional diagnostic procedures
From post infection days (PIDs) 2, twelve out of 18 animals showed pyrexia up to 42°C, which persisted throughout the observation period
As recorded by virus detection in the serum samples, started at PID 2 in three animals and at PID 3 all the animals but two became viraemic, as it was shown by the Virus isolation (VI) assays
Summary
The aim of this study was to compare the tissue distribution and pathogenicity of three virulence variants of classical swine fever virus (CSFV) and to investigate the applicability of various conventional diagnostic procedures. Virulent viruses cause peracute or acute forms of the disease with high morbidity and mortality in pigs, irrespective of age and breed. In the last three-four decades, the most common clinical picture of CSF has changed from acute to subacute, chronic or inapparent forms [4,5] These changes in the clinical manifestation of the disease frequently complicate the early detection and proper diagnosis of the CSF, considering that the very mild clinical symptoms might be overlooked. The delayed diagnosis may cause uncontrolled spread of CSF and heavy losses in large swine populations Considering this situation, there is a high need to perform comparative studies on the tissue distribution of various variants of the virus in order to study virus biology and to assure the diagnosis
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