Observation Of Pathologic Changes And Study Of Synthetical Control On PMWS In Luoyang Area

Post-weaning multisystemic wasting syndrome(PMWS)is a globally emergent epizootic disease of swine.The disease is mainly described in pigs aged 6-12 weeks and is manifest clinically by mortality,ill-thrift(wasting),paleness,dyspnea,intermittent diarrhea and visibly enlarged lymph nodes.Since its first description in Western Canada in 1991,the disease has rapidly spread to all the major pig producing countries of the world including Europe,the Americas and Asia.Most recently,the disease was reported in several countries that were previously considered free of the disease(New Zealand and Sweden).PMWS is one of the most common forms of porcine circovirus associated disease(PCVD)on a global scale.PCV-2 has been associated with a number of non-PMWS disease conditions,including porcine respiratory disease complex,porcine dermatitis and nephropathy syndrome(PDNS),granulomatous enteritis,and occasional reproductive disorders.By using enzyme linked immunosorbent assay(ELISA),941 serum samples from partial intensive pig farms in Luoyang area were tested for antibody against PCV-2.The results were as follow:OD₆30 of 19.02%(179/941)checked sera samples was≥0.42, which was regarded as positive.The positive rates in sows,breast-feeding piglets (20-day-old),post-weaning piglets(40-day-old),growing pigs(80¹00-day-old), growing pigs(150¹80-day-old) were 40.96%(68/166),6.01%(11/183),7.07%(16/203), 18.14%(39/215)and 26.44%(46/174) respectively.By the epidemiological investigation and laboratory diagnosis technology,the pigs with PMWS were collected,which showed signs of wasting,paleness,intermittent diarrhea,dyspnea,enlarged inguinal lymph nodes,and occasionally jaundice.As the usual ordinary way,the kidney,liver,lung,spleen,lymph node,cecal tonsil,thymus of pigs with PMWS were fixed,formalin-fixed,paraffin-embedded,stained with HE.The pathologic changes were observed using microscope.The results were as follow:lesions in kidneys were the multi-interstitial nephritis;the epithelial cells of uriniferous tubules falling off;infiltration of inflammatory cells surrounding interstitial.Lesions in lungs were interstitial pneumonia;infiltration of inflammatory cells.Congestion in the livers is serious,and the connective tissues among hepatic-lobules are proliferated in the liver. The structure of lymph nodule and splenic nodule were incomplete,in which the B cell decreases,while the T cell of the periarterial lymphatic sheath increases,the paracortex zone of the lymph node got thicker,in which the number of the T cell also increased.The structure of lymph nodule in cecal tonsil were incomplete,the number of lymphocyte reduced.Thymus was infiltrated by lymphocyte and eosinophilic granulocyte.Spleens,lungs,livers and lymph nodes of pigs with PMWS were collected to make autogenous vaccine,the piglets in test were vaccinated.At the same time,we did the vaccination of PRRS and used antibiotics to prevent the secondary infectious.We didn't take these measures in control,but the breeding was the same.The result was that the survival rate of piglets at the age of 90 days was 87.37%in test,but 44.19%in control(p<0.01).