| Porcine epidemic diarrhea(PED)is an acute intestinal infectious disease which is caused by the porcine epidemic diarrhea virus.The main clinical symptoms of the disease are diarrhea,vomiting and dehydration.The disease mostly occurs in the cold season.It is also a disease spreading widely around the world,which has caused severe economic damage to the pig industry.In this study,7 types of PEDV strains in Guangdong province in winter in 2016 were collected for analyzing the prevalent trend and the genetic variations.By a comparison of the M and N gene with reference strains,we found that the similarity of nucleotide between the 7 samples were 97.6%-99.9%?92.6%-99.4%,respectively.The M gene identity between 7 types of PEDV strains andreference strains of CV777 ? C H/S ? DR13/virulent ?USA/Colorado/2013? TTR-2/JPN/2014?Italy/7239/2009 and L00721/GER/2014 were 93.8%-94.8%?93.6%-94.6%?93.5%-94.5%?93.9%-96.1%?93.6%-95.8%?93.1%-94.1% and 93.9%-96.1%,respectively.The N gene identity between 7 types of PEDV strains and the above reference strains were 91.3%-95.8%?92.0%-96.5%?92.8%-96.8%?95.1%-99.2%?94.9%-98.9%?92.6%-96.5%?94.9%-98.8%,respectively.The 7 types of PEDV strains had the homology rate of above 90%with the reference strains.It proved that PEDV epidemic strains in Guangdong had the characteristics of diversity.There were many methods for prevention and control of porcine epidemic diarrhea,such as vaccine immunization,feeding,oral iodine chemicals and using mixed monoclonal antibody,immune serum,yolk antibody Ig Y and other biological products to obtain passive immunity.There was no very effective vaccine to control the occurrence of PED,and the domestic vaccine were mainly attenuated vaccine and inactivated vaccine.In order to explore the effective method of prevention and control of PED,this study was conducted to explore the effect of the prevention and treatment of PEDV in piglets by using PEDV Ig Y.Experimental group were divided into the prevention group,the treatment group,the positive group and the negative group.The prevention group was fed with 4m L Ig Y before 3 days infected with PEDV and the treatment group was fed with 4m L Ig Y after infection.DMEM culture medium was administered in the negative group.Then the piglets were dissected after 7 days with infection.C hanges in body temperature and body weight of piglets were recorded during the period,using fluorescence quantitative PCR to detect the amount of detoxification in prevention group and treatment group,and to detect the viral load of piglets.Ig G and s Ig A antibody levels in serum of piglets were detected by using ELISA kit.After dissection,small intestine of piglets was made into histopathologic slide.Immunohistochemical test and histological observation were carried out.The pathological condition of piglets was observed.The results showed that the amount of excretory virus reached the peak in the prevention group and the treatment group after infection in 1-2 days.Then the amount began to gradually reduce after infection in 2-7 days.After 7 days,almost no PEDV was detected in the small intestine of Ig Y group,and the difference was not significant compared with the negative control group.The Ig G and s Ig A antibodies in serum were not significantly different.Histopathological and immunohistochemical results showed that there was no difference between the control group and the prevention group,as well as the treatment group and the control group.These results indicated that the prevention and treatment effect of Ig Y on the piglets infected with PEDV were not ideal.In this study,through the strengthening of feeding and management,effective biosecurity measures and reasonable immune mechanism and other comprehensive prevention and control measures,ultimately the PED was successfully controlled,achieving good results. |
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