2022-2024年四川省眉山市病死猪圆环病毒感染及猪群免疫效果调查OA

In order to investigate the infection status of porcine circovirus(PCV)in dead pigs and the immune effects in vaccinated pig populations in Meishan City,Sichuan Province,pooled oronasal swab samples were collected from dead pigs on 722 farms/smallholders in 7 districts/counties in the city from 2022 to 2024,for nucleic acid detection of PCV2,PCV3 and PCV4 using fluorescent PCR kits,followed by statistical analysis by year,time period,geographical region and co-infection.Meanwhile,1 080 serum samples were collected from vaccinated pigs on 72 farms/smallholders from 2023 to 2024,to detect PCV2 antibodies using ELISA kits.The results showed that,for the period from 2022 to 2024,the average annual detection rates of PCV2 and PCV3 were 64.82％and 24.52％,respectively,but that of PCV4 was zero;the detection rates of PCV2(65.99％,74.25％)and PCV3(29.63％,33.53％)during the periods from June to September and from October to December were significantly different(P＜0.05)from those from January to May(57.36％,12.79％);the detection rate of PCV2 was slightly different(P＞0.05)between plain valley areas(62.50％)and mountainous/hilly areas(66.22％),but that of PCV3(29.78％,21.33％)was obviously different(P＜0.05);the detection rates of PCV2+PCV3 co-infection in 2023 and 2024(19.28％,23.55％),as well as those during the periods from June to September and from October to December(22.90％,29.94％),were found to be significantly different(P＜0.05)compared with those in 2022(12.55％)and during the January-to-May period(6.20％),respectively.The average annual PCV2 antibody positivity rates in 2023 and 2024 were 86.85％and 85.56％,respectively,with no significant difference(P＞0.05).In conclusion,PCV2 infection was widely distributed and severe in dead pigs in Meishan City,indicating a trend of co-infection with PCV3,especially in the period from June to December,and serious for PCV3 infection in plain valley areas;and current corresponding vaccines failed to completely fight against PCV2 infection.Therefore,vaccination programs should be optimized by replacing vaccines with those adapted to local predominant PCV2d genotype,and the harm caused by PCV to pigs should be reduced through comprehensive prevention and control measures,standardized movement of live pigs and intensive monitoring of pathogens,especially during the period of high incidence.