Diagnosis Of S.enteritidis Infection In Broiler And Study On The Preliminary Control Measures

Salmonella enteritidis which belong to the host non-specificity and invasive pathogens,causes human bacterial food poisoning by contaminated animal products, most of all,poultry and eggs are the most serious infective agent.Salmonella enteritidis infection have changen from subclinical infection and digestive disorders to septicemia and cellulosic exudative inflammation with the intensification of the poultry industry, raising its economic losses in the poultry industry and the threat to human health.Since July 2007,broiler which characterized with cellulosic exudative inflammatory diseases have been treated with amoxicillin,gentamicin and other antibiotics,the result show that there is poor of effect and serious economic losses in Chongqing region.In this paper,we diagnosis with the epidemiology,etiology and pathology of the disease,and study on the control measures preliminary,the main outcome summarized as follows:1.Epidemiological investigationThrough veterinary clinics and on-site investigation,the ratio of cases which characterized with cellulosic exudative inflammation is 49.1%(86/175) in the 175 investigated cases.In which,the ratio of 0～3-week-old broilers cases to the total cases is 26.7%(23/86),3～6-week-old is 40.7%(35/86),older than 6-week-old is 32.6% (28/86);the disease-prone in the winter and spring seasons,the number of cases is 1.6 times to the number of cases in summer and fall seasons in the veterinary clinics investigation,the morbidity and mortality is 1.46 times and 2.32 times to that of summer and fall seasons of in the on-site investigation;The feeding levels also effect the morbidity and mortality,they are 37.3%and 17.1%respectively in lower level, 15.3%and 6.6%in higher level;The use of antibiotics in high-dose and long-term also existence in all of the investigated nurseries.2.Isolation and Identification of Salmonella enteritidis From July 2007 to June 2008,we purified 30 bacteriaes from the cases which characterized with cellulosic exudative inflammation by the use of nutrient agar plate SS,and identified 26 strains Salmonella enteritidis by physical and chemical properties. 26 strain bacterials can cause 12-day-old broilers to death respectivly by subcutaneous injection with 4.0×10⁹ CFU/0.5mL,pathological symptom is consistent with the clinical cases.PCR amplification obtained DNA fragment which consistent with the theory of the size by the use of Salmonella enteritidis F14 gene specific primer sef-F and sef-R. Bacterial 16SrRNA PCR amplification obtained 1505bp nucleotides from the strains of CQ0709 by the use of the universal primer(16S-8F/20) and(16S-1512R/21).its similarity is above 99%with the reported 16SrRNA partial gene sequence of Salmonella enteritidis.Invitro results showed that the isolated 26 bacterias are resistant to amoxicillin,gentamicin and ciprofloxacin etal,present multi-drug resistant seriously, but sensitivity to drug that were prohibitted to use in clinical,such as Sulperazon, Minocycline and furadantin.3.Histopathological changesOrganizational changes occurred mainly on heart,liver,spleen,kidney and other organs in the natural case.Myocardial fiber swelling,striations blurring and red filamentous exudative cellulose in pericardial membrane;hepatocyte swelling,hepatic sinusoid congestion,liver capsule thickening with a red mesh cellulose;spleen central artery endothelial cell swelling,acinus lienis hyperemia and necrosis;glomerular swelling,swelling of capillary endothelial cells,cysts narrow tubule uneven cytoplasmic staining and granular degeneration.4.The protective effect of Inactivated vaccine and antibodiesPreparate inactivated oil emulsion vaccine of Salmonella enteritidis strain CQ0709. Inoculate 5-day-old broiler Sanhuang subcutaneously with 0.5ml/feather(2.0×10⁹ CFU),attack with 10×LD₅₀ bacterium strain CQ0709 after 15d when antibody titer is 1∶8 by AGP,the protection rate is 100%(11/11),while the incidence and mortality rates were 100%(11/11) and 81.8%(9/11) in the oil-adjuvant control group.Immunize 12-day-old broilers passively with SE-antibodies(2ml/feather,1ml/feather and 0.5ml/feather of each group)which are produced by laying hens,attack with 10×LD₅₀ bacteriums strain CQ0709 after 24h,the protective rates are 100%(11/11),100%(11/11) and 63.6%(7/11) respectivly,rather than all animals died in egg yolk-free control group.