| Foot-and-mouth disease(FMD)is an acute and highly contagious disease caused by FMD virus(FMDV)which can infect pigs,cattle and sheep.At present,the main serotypes of FMDV in China are O and A types.Pigs infected with FMDV appeared the clinical symptoms of high fever and blister as erosion in the mouth,nose,breast and hoof.In addition,it is easy to cause bacterial secondary infection,which caused huge economic losses to the pig industry in the world.There are 45 thousand sows in the farm and one million commercial pigs are sold annually in Shanghai Farm at present.Immunization is an important measure to prevent swine FMD,while the immune effect depends on the scientific immunization schedule and the quality of the vaccine.In order to select the optimum vaccine and determine the first immunization time for the piglets,evaluation of immune efficacy for O-A bivalent vaccine and monitoring of pig FMD-O maternal antibody were carried out by us.1.In the Shifeng piggery of Shanghai Farm,1806 FMDV antibody negative healthy piglets were randomly divided into four groups.There were 600 piglets in group 1(East unit 1),596 piglets in group 2(East unit 3),and 580 piglets in group 3(East unit 4),and three brands of FMDV O-A bivalent vaccine,V1,V2 andV3,were inoculated respectively.There were 30 piglets in group 4(East unit 4)and no vaccine was inoculated as negative control.Group 1?2?3 were immunized three times and antibody levels were detected by two different brand kits 28 days after each immunization.The results showed that the safety of the three vaccines was good and no severe stress reaction occurred after vaccination.The results of antibody monitoring showed that the experimental data detected by two test kits were different between FMDV-O and FMDV-A,and they indicated the antibody levels stimulated by V2 and V3 vaccines were similar and relatively high,while it was relatively low stimulated by V1 vaccine.Furthermore,theantibody positive rate of V1 vaccination group was significantly lower than that of V2 and V3 vaccines.Considering the economic cost comprehensively,the V3 vaccine is recommended as the final choice.2.Twenty healthy pregnant sows and 100 piglets(5 piglets for each sow)were selected from eachpiggery of Shenhe,Haidi,Wanzhuang,Anfeng and Shifeng in Shanghai Farm,respectively.The selected pigs were vaccinated with FMDV V3 vaccine and each maternal antibody titer was detected.Blood samples were collected through jugular vein and sera were separated from sows one week before delivery and piglets at different ages for the detection of FMDV O antibody.The results showed that the maternal antibody level in piglets decreased gradually with the increase of age.In the five piggeries,the average value of FMDV antibody titer below the threshold(5 log2)was 35,63,35,42 and 63 days old respectively,which indicates that the first immunization time in each piggery can be 28,56,28,35,56 days old(one week before the maternal antibody reduced the critical value).In addition,the FMD-O antibody titer of sows one week before delivery were 9.6 log2(Shifeng piggery),9.9 log2(Haidipiggery),8.4 log2(Anfeng piggery),6.5 log2(Shenhepiggery)and 7.5 log2(Wanzhuang piggery).The results suggest the duration of maternal antibody in piglets was prolonged with the increase of antibody level in sows,indicating that the first immunization time of piglets can also be determined according to the antibody level of sows in field production. |
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