| In this study, 755 serum samples from 11 pig farms in Luoyang were examined with the porcine circovirus type 2 ELISA antibody detection kit against PCV2-ORF2 protein to determine the prevalent status of PMWS. The results showed that all 11 farms are all positive for PCV2. Average antibody positive rate was 52.32%(395/755). The serologic positive rates of weaning piglets (40-70ds), growing pigs and multiparous sows were 41.83%(105/251), 51.37%(150/292) and 66.04%(140/212) , respectively. These findings suggested that the positive rate for the antibody against PCV-2 is high on pig farm in Luoyang. Meanwhile, the positive rate was between 32.26% and 60.42% among different pig farms, and it would increase with the pig's age raising.After H.E. Staining, the organs of the weaning pigs with PMWS were observed for histopathology. Rubber-like lesions in the swelled lungs, and interstitial pneumonia, liver congestion, edema and atroply were seen macrographicly. There were granule deformation in hepatocyte, interstitial of hepatic lobule proliferative, a lot of lymphocytes and neutrophils, duct atrophic in affected pigs. Petechia on the surface of kidneys, multifocal and interstitial nephritis ocurred, and a lot of lymphoctes soakage between renal tubules, the shedding epitheliums and proteinuria were abserved in kidneys. The lymph nodes were swelling and yellowing, the structure of lymph nodule was not complete, the paracortex of it became broadened. Spleens were swelling, some of them were atrophic, structure of splenic corpusde was abnormal or disappeared (coagulation necrosis), The numbers of lymphocytes in periarterial lymphatic sheath were more than that of health animals.In oder to investigate into the protective measures of PMWS in deep degree , some protection experiments had been carried out on the pig farms suffered from PMWS . In the current trial, 15-day-old piglets were vaccinated with native killed vaccine, which was made of the organs of piglets with PMWS and combined with vibramycin, azithromycin, florfenicol, APS,Tiamulin,doxycycline etc. This measure enhanced the survival of susceptible piglets largely.Experiment I: 162 piglets from 16 broods have been vaccinated with native vaccine , and some medicines. PMWS hasn't occurred in these experimental animals. The survival rate of 60-day pigs was 89.51% and that of 90-day-old pigs was 87.65%. Experiment II: 162 piglets from 16 broods were treated with these medicines, the epidemic disease occurred after weaning.The survival rate of 60-day-old pigs was 80.61%(133/165). 90-day-old pigs was 25.15%(124/165).While the control group (41 pigs from 4 broods) was tested using the same prevention program as before, and the disease occurred after weaning, the survival rate of 60-day-lod pigs was 53.66%(22/41). The 90-day pigs was 43.90%(18/41). The difference of survival rate between experimental group and control group was significant by t test method (P>0.01), and the survival rate of experiment I was also distinctly different from experiment II (P<0.05).
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