| Hog cholera (HC), also known as the classical swine fever (CSF), is a highly contagious disease of pigs caused by classical swine fever virus (CSFV). It is a listed disease of the World Organization for Animal Health (OIE). The only natural hosts of CSF include the domestic pigs and wild boars. At present CSF is still prevalent in China, and immunity failures have been reported frequently, which makes it difficult to defend the CSF. The objective of this study was to establish a prevention and control model against CSFV spread in the pig farms in Guangxi.Firstly, CSFV antibodies levels in the sera of pigs from the different immunity dosages and births, as well as maternal antibodies, were investigated to establish the reasonable immunization procedure with the blocking ELISA method. At the same time, two methods, blocking ELISA and forward IHA, were applied in different pig farms and the results were as follows:A. CSF live vaccines derived from spleens and cells were used to immunize 80 weaned pigs in the same farm with 4 different dosages (1,1.5,2 and 3 shares), respectively and CSFV antibody levels in piglets were examined. The results showed that piglets with the fastest increasing speed of antibodies were those immunized with the dosage of 2 shares, followed by the piglets immunized with the dosage of 3 shares, and piglets with the slowest increasing speed of antibodies were those immunized with 1 and 1.5 share of dosages. And CSF live vaccines derived from spleen were better than that of cell origin.B. Six one-month-old sows with 1-5 births received the dosages of 2 shares of the CSF live vaccines derived from spleens.The antibody changes around the immune time were detected in the sows with different births. The result indicated that the increasing rate of antibodies in the sows with 5 births was fastest, the second was sows with 4 births, the third was sows with 3 births, and that in the sows with one birth was the slowest.C. The antibody levels in the sows with 1-5 births postpartum 40d and 40-days-old piglets in the same pig farm were detected. It is found that the former was higher by 6.02～11.2% than the latter. The levels of antibodies between piglets and sows showed direct correlation. Antibodies of both were dropped along with the duration of lactation period and the dropping speed of maternal antibodies in piglets was much faster than that in sows. In the sows positive rates of antibody were 100%,96%,85% and 76%, respectively at postpartum 10d,20d,30d and 40d. The sows with the higher birth, got higher level of antibody. In the piglets the positive rates of antibody were 82%,74%,66% and 46%, accordingly. Pigs with negative antibody could not prevent against wild CSFV infection and there was a risk of excreting and diffusing CSFV. Only 4% sows couldn’t prevent against wild CSFV infection at the postpartum 20d and 24% at 40d postpartum. The positive rate of antibody against CSFV was only 46% in piglets at 40d postpartum, and therefore CSF vaccines for piglets were in need.D. Twenty 25-days-old weaned pigs were injected CSF live vaccines derived from spleens with doseage of 1 share in a farm. The antibody changes around the immune time were detected in piglets. It were found that there was no positive antibody at 4d.The positive rates of antibody were 43%,58%,76%,100%,85%,66%,48%and 32% respectively from 10d to 80d at regular intervals(an interval of 10 days) and it was highest at 40d.E. Eight hundreds of sera samples from the different growth stages of pigs in five pig farms of Guangxi were collected and antibody levels were detected using IHA method. Three hundreds and four samples from two pig farms in Guangxi of that were detected by the blocking ELISA test. The difference between the two methods was compared at the same time. The results showed that both methods could be used for detection of antibodies against CSFV, and there was only about 62% coherence between the antibodies titers by the two methods on parallel. The sensitivity of blocking ELISA was higher than that of IHA.Secondly,1614 sera samples from six boar farms in 2006 were detected for CSFV glycoprotein Erns by ELISA kit to discuss relationship between serum antibodies and the positive rate of CSF Glycoprotein Erns (gp44/48).It was found that pig farms in Guangxi were infected by wild CSFV, and the average positive rate was 25.22%(407/1614). Comparing the IHA and ELISA antibodies with positive rate of glycoprotein Erns, it was found that any antibody titer of the two methods without exception might appear positive glycoprotein Ems and there was no direct linear relationship between them, but when sera antibody titers were lower or higher, it was also higher to the positive rate of glycoprotein Ems.Thirdly,CSFV was detected in Guangxi herd, and the results by using CSFV glycoprotein Ems (gp44/48) ELISA, CSFV antigen ELISA, RT-PCR and fluorescent antibody dying technique were compared. At the same time the glycoprotein Ems antibody levels by forward IHA and blocking ELISA were compared. The results were as follows:850 whole blood samples were detected by CSFV antigen ELISA test from 2006 to 2007 and the positive rate was 8.94%(76/850). From 2005 to 2007, by using RT-PCR method 434 samples of organic tissues from pigs died of illness were detected and got 10.14% positive rate (44/434).Besides, the positive rate was 3.87%(51/1317) in 1317 samples of boar semens and 2.65% in the sow tonsils (23/867).250 samples detected with fluorescent antibody dying method and the positive rate wasl7.2%(43/250) in 2006 and 200 samples of pig tonsils were negative in 2007.Fourthly,the samples of sera, tonsil and the whole blood from two pig farms were detected, respectively, by using CSFV glycoprotein Ems (gp44/48) ELISA, CSFV antigen ELISA, RT-PCR and fluorescent antibody dying technique. The results showed that fluorescent antibody dying technique got the highest positive percentage, and RT-PCR was the second. CSF antigen ELISA method got the third, but had the best reproducibility. Though CSFV glycoprotein Ems ELISA was the lowest positive percentage, it could determine the pigs infected by wild CSFV and there was 75% consistency with the CSF antigen ELISA. Tonsil got the best repeatability among the three samples for testing.The incidence of CSF decreased gradually by eliminating CSFV-positive pigs. The positive rates decreased from 27.45% in 2004 to 2.25% in 2007 in the pathological samples, from 8.11% in 2005 to 0.3% in 2007 in sows and from 6.67% in 2005 to 0 in 2007 in boar semens. |
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