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A swine vesicular disease virus (SVDV) replication assay in IB-RS-2, SK-6, and PK-15 cell cultures was performed using the xCELLigence system. The cell status was monitored by impedance measurement, expressed as cell index (CI). Proliferation of particular cells was examined at the beginning of the study. The cells exhibited the ability to form a monolayer, and the CI values increased with the cell culture growth. After about 23 h and while still in the growth phase, the cells were infected with decimal virus dilutions (10⁻¹-10⁻⁶) containing from 100 000 to 1 median tissue culture infectious doses (TCID₅₀). SVDV replication in cell cultures induced a change in cell index; together with the occurrence of cytopathic effect (CPE), the CI values declined. A significant correlation between the concentration of the virus used and CPE occurrence was found. The results also enabled determination of cell sensitivity to SVDV infection. The highest sensitivity was exhibited by IB-RS-2, followed by SK-6. To conclude, the xCELLigence System was used effectively and evaluated as being an efficient tool for CPE detection and SVDV replication analysis in cell cultures. Compared to the standard method, it enabled a more precise assessment of viral replication based on the quantitative CI measurement, providing additional current information.
The period of swine vesicular disease (SVD) virus persistence in clinical and tissue samples from experimentally infected pigs was investigated. A range of samples including epithelial tissue from vesicles, nasal swabs, blood, faeces and organs were collected to examine for the presence of infectious SVD particles, genomes and antigen. For this purpose, the conventional and PCR techniques were applied. The RT-nPCR assay appeared to be the most sensitive for the detection of SVDV in samples taken late in the course of infection. Only by nested PCR we could found the presence of vRNA in blood and nasal swabs as long as 4 and 48 d.p.i. , respectively. Using virus isolation and RT-nPCR it was possible to detect viral genome in faeces up to 70 d.p.i. By RT-nPCR, the vRNA could be detected in somatic muscles and tonsil till 25 and 48 d.p.i., respectively. The virus could not generally be found in other organs beyond 7 d.p.i. The described RT-nPCR procedure can be useful for the duration estimation of infection of pigs with SVDV.
Application of real-time RT-PCR (rRT-PCR) for detection of swine vesicular disease virus (SVDV) in samples of archival SVDV isolates and clinical samples collected from SVDV infected pigs was described. A primer set that targets the IRES region of the SVDV genome and TaqMan probe specific for a highly conserved region in SVDV RNA IRES region were used. The assay detected viral RNA in all tested archival strains of SVDV isolated in Europe during years 1972-73 and 1992 as well as in clinical samples collected from experimentally infected pigs. The rRT-PCR can provide quantitative and qualitative information and is more sensitive and faster to perform than the conventional RT-PCR.
Senecavirus A (SVA) is a single representative species of the Senecavirus genus within the family Picornaviridae. This review presents the current knowledge regarding SVA epidemiology, transmission, pathogenesis, clinical signs, differential diagnosis and control measures. SVA is not debilitating, but significant because of its resemblance to acute, highly contagious and economically devastating viral diseases, such as FMD. The incubation period of SVA is 4-5 days, the viremia period is short, lasting 3 to 10 days post infection (dpi). SVA shedding lasts up to 28 days. SVA can be shed by oral and nasal secretions and by faeces. The virus excretion peak occurs between 1 and 5 dpi, especially in oral secretions, which contain higher virus loads relative to nasal secretions and faeces. SVA lesions are found most frequently on the snout, lips and tongue, as well as on hooves, specifically, on coronary bands, dewclaws, hoof pads and in interdigital space. The vesicles quickly rupture to form ulcers that may be covered by serofibrinous exudates. The ulcers begin to repair in 7 days, and the regeneration of epithelium is usually complete within 2 weeks. Since clinical lesions induced by SVA are indistinguishable from those observed in other vesicular diseases of swine, accurate and reliable laboratory differential diagnosis is critical to the precise identification of the infectious agent. SVA has potential cytolytic activity and high selectivity for tumour cell lines with neuroendocrine properties versus adult normal cells. Because of its potential oncolytic activity, the virus can be useful in human cancer therapy. The example of SVA shows that the risk of emerging infectious diseases in swine populations is high and that emerging diseases of swine have significant potential impact on the productivity and economics of the pork industry. The SVA infection is currently limited to the United States, Canada, Brazil, China and Thailand. However, descriptions of the SVA infection in Asia suggest that the virus is not restricted to a specific geographic region and may be distributed on a global scale in the future.
The aim of this studies was the genetic analysis of Polish SVDV isolates from 1972-73. The direct nucleotide sequencing technique of PCR products from the 1D (VP1) structural polipeptyde coding region was applied. The genetic differences between Polish isolates and other European and Japanese ones from 1966-1994 were determined by comparing their nucleotide sequences. No considerable genetic divergences were found between Polish isolates and the others in 1972-1981 . This suggests a close relation and common origin of all isolates belonging to genogroup II. The considerable genetic differences (10-15%) were found between Polish strains from 1972-73 and West European isolates from 1991/92 (genogroup III) and 1993/94 (genogroup IV). These results indicated that distribution of isolates within these genogroups appears to be more related to the year of their collection than to their geographical origin. The obtained results can be important information for epidemiological studies of SVD in Europe.
A nucleotide sequence analysis by RT-PCR and cycle sequencing of the Polish isolate of swine vesicular disease virus (SVDV) was performed. The RT-PCR products pattern and VP1/2A coding region sequence were compared to the other available European isolates of SVDV and the human Coxackie virus isolate CAV-16. The results of the RT-PCR show that it is possible to detect different isolates of the SVDV however Coxackie virus-specific PCR products were obtained only by the use of one from three selected primer pairs. A sensitivity of the used RT-PCR was equivalent to that of virus isolation in cell culture and even higher than the ELISA method. The considerable nucleotide similarity between the Polish isolate UKG27/72 and the Japan 76 SVDV isolates (99% and 98%, respectively) as well as the CAV-16 (96%) was found. SVDV Poland 73 was genetically less related (about 88%) to the Dutch and Italian isolates from the recent outbreaks of disease in 1992. Presented results confirmed the quasispecies character of these picornaviruses.
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