Serological Investigation And Curative Effective Study On Haemophilus Parasuis Disease In Scale Pig Farms

Haemophilus parasuis disease,also known as Gl?ssers Disease,is a kind of contagious respiratory infectious disease caused by the bacterium Haemophilus parasuisresulting fibrinous polyserositis,meningitis,pleuritis and arthrophlogosis.It infects pigs in all ages,especially pigs aged 4 ~ 6 weeks.Nowadays,it is one of the major diseases affecting health of weanling pigs and nursery pigs.With the rapid development of intensified and large-scaled pig breeding in China in recent years,the infection of Haemophilus parasuis disease has increased distinctly and caused heavy economic losses in pig industry.This research conducts relevant studies on Haemophilus parasuis disease in some scale pig farms in Shaanxi Province,including epidemiological survey,bacteria isolation and identification,drug sensitive test,histopathology,pathogenicity and curative effect test,which lays the foundation of diagnosis,prevention and control of this disease.Here are some main results.1、By means of IHA,the epidemiological survey shows that the positive rate of three scale pig farms is 24.80%,29.60% and 14.80% respectively,among which pig farmⅠis the highest one with 5.20% and 10% higher than pig farm Ⅱ and pig farm Ⅲ,Significant difference(P<0.05).In these three pig farms,the positive rates of pig aged 30-day,60-day,90-day and 120-day and female pigs respectively are 32.67%,25.33%,20.67%,13.33% and 6.67%,among which 30-day-pig has the highest rate 32.67%,with 7.34%,12.00%,19.34% and 26.00% higher than those of 60-day-pig,90-day-pig,120-day-pig and female pigs,Significant difference(P<0.05).2、Tissues of infected pigs,such as heart,liver,lung,lymphaden and synovial fluid,are taken for bacteria isolated culture,biochemical test and drug resistance test.The result shows that all 42 isolates are coincide with traits of bacteria Haemophilus parasuis,including one serotype 1(2.38%),eight serotype 4(19.05%),fifteen serotype 5(35.71%),three serotype 12(7.14%),eleven serotype 13(26.19),one other serotype and three unidentified serotype.The drug sensitive test indicates that the isolate is highly sensitive to azithromycin,cotrimoxazole,florfenicol and lomefloxacin,moderately sensitive to levofloxacin and semiantigen sulfamonomethoxine,and insensitive to ceftiofur sodium and doxycycline.3、The gross anatomy manifestsfected pigs,even with adhesion in severe cases.Other features include pericardium thickening hemorrhagic spots,liver congestion and enlargement,lungs enlargement with red,white or grey stripe on the surface,spleen congestion and enlargement with hemorrhagic infarcts on the surface,hemorrhagic spots in kidney,mesenteric lymph nodes enlargement hemorrhagic spots,hemorrhagic spots in the mucosal side of large and small intestine,and arthroedema.Histopathologic observation include cardiac muscle fibres breakage;obvious flocular degeneration and vacuolar degeneration in cardiac muscle;pulmonary lobules interstitial edema;most alveolis disappear with remained alveolis vicarious enlargement;vasodilatation;fiber connective tissue hyperplasia with focal cellular infiltration;hepatic cells swelling with irregular arrangement and vacuolar degeneration;hepatic sinusoid expanding;germinal center of splenic corpuscle disappears or diminishes with a few of lymphocytes remain;glomerulus atrophy;capsular space widens with inflammatory exudate.4、Virulence test is done among 60 cavies and 24 piglets.The result shows that(1)three hours after inoculating,cavies in groupⅠ~Ⅴ successively suffer from listlessness,dyspnea and tremor.The morbidity of group Ⅲ is high reaching 90%,with 70%(P<0.01),30%(P<0.05),70%(P<0.01)and 10%(P<0.05)higher than groupⅠ,Ⅱ,Ⅳ,andⅤrespectively;while the death rate of group Ⅲ is 38.89%(P<0.01),5.56%(P<0.05),38.89%(P<0.01)and 1.39%(P>0.05)higher than groupⅠ,Ⅱ,Ⅳ,andⅤrespectively.At the same time,group CK has no symptom at all.(2)After inoculating,the morbidity of five piglets group is 100%,especially the group Ⅲ,ⅣandⅤwith 100% morbidity and 100% death rate.The death rates of groupⅠandⅡ are 50% and 75%.In terms of mean death time,highest virulence appears in groupⅢ,which is after 30 h.The death time of each group in order is Ⅲ>Ⅴ>Ⅱ>Ⅳ>Ⅰ.5、The curative effect test combining Chinese traditional and western medicine is done among 60 30-day-old piglets.The result shows that(1)the cure rate of testⅢ reaches 70%,with 30.00% and 20.00% higher than testⅠandⅡ,The difference was Significant(P<0.01).While the survival rate of testⅢ is 35.00% and 25.00% higher than those of testⅠandⅡ,The difference was Significant(P<0.01).(2)In terms of influence on the morbidity and the death rate of 20~40-day-old infected piglets,death rates of the testⅠandⅡare both 33.33% and the death rate of testⅢ is zero in 20-day,The difference was Significant(P<0.01);in 30-day,the death rate of testⅢ is 16.67%,with 33.33% lower than those of testⅠandⅡ;in 40-day,the death rate of testⅢ is 25.00%,with 37.50% and 12.5% lower than those of testⅠandⅡ respectively,The difference was Significant(P<0.01).