Investigation And Analysis Of PRRS In Large-scale Pig Farms In Changji

Porcine Reproductive and Respiratory Syndrome(PRRS)is a severe infectious disease that causes respiratory diseases in piglets and reproductive disorders in sows.Its pathogen is Porcine Reproductive and Respiratory Syndrome Virus(PRRSV),which is required by the World Organization for Animal Health(OIE).One of the notified infectious diseases.The disease presents a global epidemic trend,causing huge economic losses to the pig industry.At present,the effect of prevention and control measures for the disease is not satisfactory,which has seriously affected the development of the pig industry.Three large-scale pig farms in Changji,Xinjiang are infected with PRRSV,but the characteristics of the epidemic strain,the epidemic pattern,and the effectiveness of immune prevention and control are still unclear..Purpose:Through on-site epidemiological investigation,molecular biology and serological testing,this study explored the characteristics and prevalence of PRRS disease on three large-scale pig farms in Changji,Xinjiang,and analyzed the application effects of immune prevention and control measures.The prevention and control of the disease in this region provides a theoretical basis.Methods:(1)On-site epidemiological investigation and PCR detection were conducted on pigs at different stages of three large-scale pig farms in Manas County,Hutubi County,and Dianba Township in Changji Prefecture.The main contents of the investigation include positive rate and incidence.Season,age of onset,current status of vaccine immunity,etc.(2)Real-time fluorescent quantitative PCR detection of different strains of PRRS virus American strain and NADC-30-like strain)on 78 samples from large-scale pig farms in Hutubi County.(3)ELISA antibody detection was carried out on 1,316 serum samples from three large-scale pig farms immunized pig herds to analyze the effect of vaccine immunity and provide theoretical basis for formulating pig farm immunization procedures.Results:(1)After on-site clinical observation and PCR detection,the average diagnosis rate of PRRS on the three pig farms was 6.32%(377/5963),among which the pig farm in Manasi County was 5.05%(93/1842)and Dianba Township The pig farm is 5.45%(117/2146)and Hutubi County pig farm is 8.46%(167/1975).Among the 377 confirmed samples,the positive rate in summer was 38.72%(146/377)and the positive rate in autumn was 24.40%(92/377)higher than 18.83%(71/377)in spring and 18.03%(68/377)in winter.The incidence of nursery pigs was 10.42%(197/1891),the incidence of lactating sows was 4.90%(31/632),the incidence of lactating piglets was 4.90%(135/2753),and the incidence of breeding sows was 4.67%(14/300).(2)Fluorescence quantitative detection of PRRSV positive rate in Hutubi Pig Farm was 3.85%(3/78),and 1 sample out of 3 positive samples detectedNADC-30-like strains.(3)The positive rate of antibody detection in the three pig farms after vaccination was 92.3%(1215/1316).Among them,the Dianba pig farm accounted for 92.3%(454/492),the four quarters were 89.80%(97/108)in spring,100% in summer(51/51),93.60% in autumn(161/172),and 90.10% in winter(145/161);Manas pig farm is 88.5%(379/428),the four seasons are 80.40% in spring(74/92),100% in summer(85/85),and93.00% in autumn(120/129),82.00%(100/122)in winter;96.46%(382/396)in Hutubi pig farm,97.10%(132/136)in spring and summer,97.90%(139/142)in autumn,and 94.10%(111/ 118);According to the requirements of China’s Ministry of Agriculture for immunization against animal diseases in 2016,a pig PRRS antibody positive rate of more than 70% is qualified,indicating that the three farms have qualified immunity to pig PRRS.Among them,the four quarters of Dianba pig farm(S/P greater than 2.5)were 14.81%(16/108),37.25%(19/51),20.35%(35/172)and 6.83%(11/161);Mana The four seasons(S/P greater than 2.5)of the pig farm in Si County were 9.78%(9/92),37.65%(32/85),2.33%(3/129)and 5.74%(7/122);Hutubi Pig farm(S/P greater than 2.5)has 37.50%(51/136)in spring and summer,35.92%(51/142)in autumn and 10.17%(12/118)in winter.Combine PCR detection data and ELISA data for analysis It can be seen that when the antibody positive rate is greater than 80%,the average S/P is between 1.07 and 1.71,and the dispersion is below50,the probability of PRRSV infection in the pig herd is relatively small.Conclusion:PRRS infections exist in 3 large-scale pig farms in Changji,Xinjiang,and they are spreading in various seasons.A large-scale pig farm in Hutubi is infected with PRRSV American strain and NADC-30-like strain,and attention should be paid to strengthen prevention and control.The optimal immunization program for the three farms is to use inactivated vaccines for sows and boars,and attenuated vaccines(JXA1-R strain)for piglets.The immunization program is general immunization in spring and autumn(no immunization for sows in late pregnancy),and a supplementary immunization for postpartum sows and weaned piglets.