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.
Laboratory experience during the classical swine fever virus epizootic in the Netherlands in 1997-1998.
From February 1997 till May 1998 the national reference laboratory for classical swine fever (CSF) in the Netherlands was confronted with millions of samples taken from pigs during an outbreak of CSF in a pig dense region. In a limited period major logistic problems needed to be solved regarding the processing of samples and information at the laboratory facilities. In total over 2.3 million samples were examined by different CSF diagnostic methods. The majority (approximately 2.1 million) of these samples were blood samples which were tested for CSF serum antibody in a semi-automated ELISA. Approximately 166,000 samples were examined for the presence of CSF virus or viral antigen. Automated preparation and testing of blood samples for CSF serum antibody, the obligatory identification and registration system of pig holdings and the computerised laboratory management system made it possible to process the huge amount of samples and information presented in a limited period. The majority of the test results was sent to the veterinary authorities via e-mail or a computerised fax system. Of the 429 outbreaks 82% were detected via a direct immunofluorescence technique performed on cryostat sections of the tonsil. The sampling of clinically suspected pigs ('guided' sampling) for this diagnostic method provided rapid positive and negative results and thus played a paramount role during the eradication campaign. Serological surveys identified 13.5% of the infected pig holdings: such surveys proved very effective in the screening of holdings which were subjected to restrictions (protection or surveillance zones) for many months. Virus isolation performed on different types of samples detected 4. 5% of the infected pig holdings. In conclusion, analysis of data collected in the laboratory and epidemiological analysis should result in an improved eradication plan for the future control of outbreaks of CSF in the Netherlands supported by optimised CSF diagnostic methods.
Temperature effects on lily development rate and morphology from the visible bud stage until anthesis.
Day (DT) and night temperatures (NT) influenced Lilium longiflorum Thunb. 'Nellie White' stem elongation and development rate from the visible bud stage (VB) until anthesis. Plant height increase after VB was a function of the difference (DIF) between DT and NT (DT-NT). Plant height increased 90% as DIF increased from - 16 to 16C. A cubic model described bud development rate as a function of temperature from 14 to 30C. A linear model adequately described bud development rate as a function of average daily temperature from 14 to 21C. Based on the linear model, bud development rate increased 0.05 per day for each 1C increase in average daily temperature. The base temperature for bud development, i.e., the temperature at which bud development rate was 0, was calculated as 3.5C. Greenhouse forcing of vernalized Easter lilies is commonly divided into three phases: I) placement of vernalized bulbs in the greenhouse to flower initiation, II) flower initiation to VB, and III) VB to anthesis (De Hertogh and Wilkins, 1971). Plant morphological development differs during each of the forcing phases (De Hertogh and Wilkins, 1971). Growth during phase I is vegetative and consists of stem elongation and leaf expan- sion. Flower initiation, leaf expansion, and stem elongation oc- cur during phase II. Inflorescence expansion and stem elongation occur during phase III. Lily responses to temperature during phase III differed from those during phases I and II (Wang and Roberts, 1983). Lily development rate, quantified as days to unfold a leaf, is a de- creasing linear function of average daily temperature between 14 and 30C during phases I and II (Karlsson et al., 1988). Lily development rate during phase III is a nonlinear function of temperature (Healy and Wilkins, 1984). The effect of temper- ature on the rate of lily development decreases as DT and/or NT increase during phase III (Rob and Wilkins, 1973; Healy and Wilkins, 1984). Easter lily morphological development is thermomorpho- genie. For instance, internode length increases as the DIF be- tween DT and NT increases (Erwin et al., 1989). In addition, leaf orientation, leaf length, and flower length are also influ- enced by diurnal changes in temperature.