An Outbreak of Classical Swine Fever (CSF) in a Closed-Cycle Unit in Israel
In a closed pig holding facility containing 425 sows, located in northern Israel, a Classical Swine Fever (CSF) outbreak occurred, which caused the loss of 267 sows (62.8% of the farm sow population), 4 boars (out of 6), and 828 growing/fattening pigs (41.4% of the total on the farm), through direct mortality, partial culling, and an unknown number of abortions. The CSF outbreak started among the pregnant sows, with high fever, cyanosis, abortions, lameness, vomiting, and mortality (24.8% of sows and 33.3% boars). At necropsy, hemorrhages were found on the parietal pleura, diaphragm, epicardium and kidney; lymph nodes were congested and hemorrhagic; necrotic lesions were present on the mucosa of the small intestine. CSF was diagnosed at Kimron Veterinary Institute by reverse transcriptase polymerase chain reaction (RT-PCR) method and with ELISA-antibody test on serum and ELISA-antigen test on organ homogenates. The results were confirmed by the EU Reference Laboratory at Hanover, Germany with Real Time–PCR on blood and organs. Phylogenetic analysis showed that CSFV sequences of the Israeli virus isolates belonged to genotype 2.1. Molecular typing and comparison of amino acids with CSFV subgroup 2.1 isolates from Southeast Asia and from Europe revealed that the CSFV isolate responsible for the Israeli outbreak was genetically most similar to a Chinese CSFV isolate. Involvement of wild boars, which were in contact with sows was suspected. Samples from blood and organs taken from wild boars found in the vicinity of the farm were found positive for CSF. Following confirmation of CSF, elimination of clinically sick animals and vaccination of the remaining population in the holding and the surrounding area were implemented.
Assessment of classical swine fever diagnostics and vaccine performance.
Rapid and accurate diagnosis is of the utmost importance in the control of epizootic diseases such as classical swine fever (CSF), and efficacious vaccination can be used as a supporting tool. While most of the recently developed CSF vaccines and diagnostic kits are mostly validated according to World Organisation for Animal Health (OIE) standards, not all of the well-established traditional vaccines and diagnostic tests were subject to these validation procedures and requirements. In this report, data were compiled on performance and validation of CSF diagnostic tests and vaccines. In addition, current strategies for differentiating infected from vaccinated animals are reviewed, as is information on the control of CSF in wildlife. Evaluation data on diagnostic tests were kindly provided by National Reference Laboratories for CSF in various European countries.
Immunomodulatory effect of plasmids co-expressing cytokines in classical swine fever virus subunit gp55/E2-DNA vaccination.
The aim of this study was to determine the immunomodulatory effects of IL-12, IL-18 and CD154 (CD40 ligand, CD40L) in DNA-vaccination against the classical swine fever virus. Four recombinant plasmids were constructed including the CSFV coding region for the glycoprotein gp55/E2 alone or together with porcine IL-12, IL-18 or CD154 genes. Five groups of four pigs each were immunized intramuscularly (i.m.) three times with the respective constructs. The control group was inoculated with empty plasmid DNA. Eighteen days after the final immunization, the pigs were challenged with a lethal dose of CSFV strain Eystrup and monitored for a further 16 days. This study showed that co-delivery of IL-18 and CD154 induced an earlier appearance of serum antibodies, reduced B-cell deficiency after infection and protected pigs against a lethal CSFV infection. In contrast, co-delivery of IL-12 led to a reduced titer of neutralizing antibodies and protection against a lethal CSFV challenge in comparison to the other pigs and to pigs that were immunized with a gp55/E2 plasmid alone.