| Duck infectious serositis is also known as Riemerella Anatipestifer(RA)infection.Duck infectious serositis is an acute septicemic infective disease caused by Riemerella Anatipestifer(RA).The main pathological features of RA-infected ducklings and other birds are fibrinous pericarditis,perihepatic inflammation,and fibrinous pneumonia.Duck infectious serositis with high morbidity and mortality has caused serious harm to the ducks farming industry in the world.Sansui County belongs to Qiandongnan prefecture and has abundant water resources.It is the source and main producing area of Sansui duck,one of the four most famous ducks in Sansui country.With the strong support of the Guizhou Provincial Party Committee,the Provincial Government,the Qiandongnan Prefecture Party Committee,the State Government,local county Party committee and county government,the duck breeding industry in Sansui County has developed vigorously.Except Sansui ducks with a high egg production rate,rough feeding resistance,tender meat,delicious color,low cholesterol and poultry breeds,they also mainly breed excellent breeds such as Huabian duck and Jinding duck.As the scale of duck breeding continuously expanding,the local duck disease problem has become increasingly prominent,infectious serositis in ducks is the most common.In order to grasp the prevalence and prevention methods of duck infectious serositis in large-scale duck farms in Sansui County,this paper conducted an epidemiological investigation and preliminary study on prevention and treatment of epidemic serositis of ducks in large-scale duck farms in Sansui County,Guizhou Province.1.The epidemiological investigation of duck infectious serositis in Sansui County from 2017-2019.In order to understand the incidence regularity of duck infectious serositis in large-scale duck farms in Sansui County,Guizhou province in recent years,this study investigated the epidemiological of duck infectious serositis in 20 large-scale duck farms from 2017 to 2019.These results indicated: for the breeding season,in recent years,duck infectious serositis occurred in meat duck farms and egg ducks in Sansui County all the years round,and the incidence was higher in winter and spring and lower in summer and autumn,especially in March and May.The Average incidence rate respectively reached20.13%(72.5 thousand/359.6 thousand),18.58%(66.8 thousand/359.6 thousand)in March and May.For breeding mode,the average incidence rate of fully open duck farms was higher,reaching 27.78%(60 thousand / 216 thousand),and the average incidence of semi-open duck farms was second,reaching 23.51%(232.6 thousand/ 989thousand),the net-bed duck farm had the lowest average incidence rate,only 18.5%(67 thousand/362thousand);For breeding species,the average incidence rate of lace ducks(meat-type ducks)was the highest 30.43%(254.1 thousand/835 thousand).The average incidence rate of Jinding ducks(egg and meat combined type)was second,reaching 16.94%(81thousand/478 thousand),and the average incidence rate of Sansui ducks(egg-type)was the lowest 9.65%(24.5 thousand / 254thousand);For the age of onset,the average incidence of ducklings aged 6 to 15 days was the highest,reaching 58.9%(211.9 thousand / 359.6thousand),The average morbidity rate of ducks aged 20 to 60 days was second,reaching37.6%(115.8 thousand / 359.6 thousand).The average morbidity rate of ducks aged over60 days was lower,only 3.5%(12.6 thousand/359.6 thousand).2.Pathogen isolation and identification of duck infectious serositis in Sansui CountyIn this study,6 suspected RA strains were collected and separated from a duck farm in Sansui County,Guizhou province,and were identified by isolation and culture,physiological and biochemical identification,specific gene analysis,animal regression test,serotype identification,and virulence gene detection.Translucent and smooth circulars colony appeared on chocolate medium,gram staining shown that they were Gram negative tiny rods,Wright’ s staining showed bipolar concentrated,urea,catalase,and oxidase test were all positive.Six bacterial isolates were randomly selected,and PCR amplification was carried out with the universal primers of the bacterial 16 S r RNA gene.All DNA fragments about 1 450 bp were amplicated.After DNA sequencing,sequences comparison with RA reference strains showed that the homology reached 98.6%～99.9%.Then these 6 bacterial isolates were inoculated to ducklings respectively.The clinical symptoms and pathological changes of the inoculated ducklings were consistent with the typical characteristics of infectious serositis in ducks,and the bacteria consistent with the original inoculated bacteria could be isolated.Comprehensive culture characteristics,bacterial characteristics,biochemical identification,and animal regression test,it can be determined that the 6bacterial isolates are all RA,named SS-RA1～6 respectively.6 RA cultures were taken and sent to the Poultry Disease Research Center of Sichuan Agricultural University for serotype identification.It was confirmed that SS-RA1～4 isolates were serotype 2 and SS-RA5～6were serotype 11.PCR amplification was carried out with 8 common virulence gene-specific primers of RA,and it was found that the corresponding DNA fragments(1164 bp,1 026 bp,939 bp,585 bp,468 bp,1 164 bp,1 026 bp,939 bp,585 bp,468 bp,729 bp,427 bp and 999 bp),suggesting they all contained Omp A,CAMP,wza,AS87＿04050,Fur,SIP,Tbd R1 and lux E virulence genes.For SS-RA5～6 isolates,they could be detected except for the AS87＿04050 virulence genes.Seven other virulence genes were identified in SS-RA 5～6.3.The drug sensitivity test and its therapeutic efficacy of duck infectious serositis by sensitive antibiotics in Sansui CountyAfter the isolation and identification of RA,drug sensitivity experiments were also conducted in this study.Medicine sensitive experiment indicated that 6 isolates were sensitive to penicillin drugs(carboxy ampicillin,piperacillin)and cephalosporin drugs(cephalosporins he organism,ammonia benzyl,ceftriaxone,cefepime and cephalosporin cefoperazone),and they were resistant to aminoglycoside,tetracycline class,quinolone classes,large ring lactone class,chloramphenicol and sulfa drugs.At the same time,PCR identification showed that 6 drug-resistant genes(aac(6’)-Ib,oqx A,erm F,tet(X),flo R and Int I1)were present in all the 6 isolates,which were consistent with the results of the above drug sensitivity experiments.According to the results of drug sensitivity,the combined treatment of ceftazidime,enrofloxacin and carbenicillin was chose,which effectively controlled the case fatality rate.After continuous use for 5 days,the duck population recovered.In conclusion,duck infectious serositis can occur all year round in large-scale duck farms in Sansui County according to the results of epidemiological investigations,with a higher incidence in winter and spring,but a lower incidence in summer and autumn.Ducks of different species and growth stages could be infected with RA.6 Riemerella anatipestifer(RA)were isolated from duck farms in Sansui county by etiology identification.And,the serotype of 4 strains was 2 type,and the others were 11 type with gene detection.6 strains were sensitive to semi-synthetic penicillins and cephalosporins antibiotics and resistant to aminoglycosides and tetracyclines antibiotics.At the same time,the corresponding resistance genes were detected.In order to treat duck infectious serositis,sensitive antibiotics were used,and the therapeutic efficacy was good... |
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