| Swine influenza(SI)is an acute and highly contagious respiratory disease caused by swine influenza virus(SIV),which is widely spread all over the world.Under natural conditions,pigs are susceptible to human influenza virus and avian influenza virus,while they can transmit SIV to avian and human.Therefore,pigs are considered as "incubators" which can produce influenza virus gene recombination and new antigen subtypes,so SIV plays an important role in the ecological distribution and genetic evolution of influenza virus,animal husbandry economy and human public health.In order to understand the situation of SIV infection and determinate the subtypes of epidemic strains in Liaoning,totally 4800 serum samples of pigs not immunized with influenza vaccine were randomly collected from scale farms,slaughterhouses and scattered households in five areas within 14 cities in Liaoning between January 2016 and December 2018.Using HI method with EAH1N1,H1N1pdm09,H3N2,H5 and H7 antigens,all serum samples were tested and the data were analyzed.The results showed that the total number of serum samples positive was 2145,and the total positive rate was 44.69%.The number of type A H1N1pdm09 antibody positive samples was 1886,and the positive rates of each year were respectively 37.1%,41.37%,39.76% with no different significant,and the average positive rate was 39.29%.Quarterly analysis showed that the positive rates were 44.54%,38.57%,28.57% and 47.46%,respectively,in which the positive rates were relatively higher in the first and fourth quarters.And regional analysis showed that,the positive rates in the eastern area was highest at 44.65%,while the middle area was lowest at 29.28% among the five major areas in Liaoning.In addition,the positive rates were between 22.42%~53.46% in the fourteen cities,and the samples from Shenyang,Benxi,Dandong,Panjin and Huludao presented relatively higher positive rates,all of which exceeded 45%.For the positive rates of avian H1N1 subtypes SIV,the number of positive samples was 259,and the positive rates in each year,were 8.16%,2.54%,5.32% and 5.98%,respectively.Quarterly analysis showed that the positive rates were between 3.84%~6.97%,with no significant difference,in which the samples from southern and northern areas with relative higher positive rates,and the lowest positive rate was found in eastern area.The positive rates of antibodies in samples from fourteen cities in Liaoning were found between 1.21% and 12.73%,in which the highest positive rate was found in samples from Dalian,while the positive rates of samples from Anshan,Fushun and Yingkou were relatively lower,all of which were lower than 2%.In addition,there were 71 samples were positive for H1N1pdm09 subtypes SIV antibodies and avian H1N1 subtypes SIV antibodies,with positive rate at 3.46%,which indicated that there were co-infection with different subtypes of SIV in Liaoning.For the test of H3N2 subtypes of SIV,the number of positive samples was 21 with positive rate at 0.44%.In addition,no H5 and H7 were detected in all the samples.In summary,the serum samples of unvaccinated SIV vaccine were collected from scale farms,slaughterhouses and scattered households in Liaoning and tested using HI method to establish the monitoring network of SIV,to understand the infection situation of SIV,and determine the epidemic subtypes of SIV in Liaoning.The study provided a theoretical basis for the prevention and control measures of SIV in Liaoning region,which is important for clinical significance to decrease the threat of SIV outbreak and improve the productivity of pigs in Liaoning as well to prevent human infection. |
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