The Isolation And Identification Of Caseous Lymphadenitis And Its Serological Investigation In Dairy Goat

Nowadays,intensive breeding of dairy goats has become the main development directio n of China’s dairy goat industry.Because of the competitive advantage of the goat milk price,there are a growing number of areas for the breeding of dairy goats,for example Henan,Heilongjiang,Fujian and Guizhou province.Intensive farming model has been generally accepted by farmers in the main breeding province of China.Whereas,infectious disease in dairy goat is still one of the main factors that seriously restrict the healthy development of dairy goat industry in China,especially the chronicdisease of Caseous lymphadenitis(CLA or cheesy gland),which is caused by Corynebacterium pseudotuberculosis(CPTB).It causes too expressive losses in weight,production and reproductive efficiency,and what is more,as containing a certain number of pathogenic bacteria,milk of lactation sheep gives rise to s potential safety hazard to physical health of consumers who enjoy drinking fresh milk.Altthough CLA infection has been widespread,accurate epidemiological survey data of CLA is still a blank,which is one of the main problems that this study should solve.This study collected pus of suspected CLA goats from Fuping Shannxi,Longxian Shannxi and Luxi Yunnan.Though bacteria separating culture,microscopic examination,biochemic a l test,collaborative hemolysis test,PCR,animal pathogenicity test and et al.,this study has accomplished isolation and identification of pathogenic bacteria,while completing antibodies assay of CLA through CLA-indirected-ELISA.The results are as follows:1.There were 3 bacterial strains Fester samples isolated from the samples of the dairy goats in Fuping of Weinan city,Longxian of Baoji city and Luxi of Yunnan province respectively.Bacterial strains was characterized by poor growth and coming into being gray circular small dry colony,easy to be moved and broken on LB medium.Nevertheless,tip shape small colony was observed on blood agar plate,which appeared β-hemolytic narrow band and became opaque,pale,concentric,fraze,and convex.Meanwhile,inoculated with the isolates,LB liquid medium became micromixing,coming into being with the white pellicle.While standing stil,it usual y formed a surface pellicle and granular deposit,which benefiting from by the addition of serum.This microorganism is a facultative pathogen that exhibited pleomorphic forms,such as coccoids and filamentous rods.It is non-sporulating,non-capsulated,non-motile and Gram-positive,although such staining may sometimes be irregular.It tend to show a characteristic palisade or ‘‘Chinese letter’’ arrangement in smears.The biochemical characteristic was consistent with Corynebacterium pseudotuberculosis described by Bergey’s Manual of Determinative Bacteriology.2.The isolates were able to appear hemolytic synergism with Rhodcoccus equi on solid blood-containing media.3.After molecular biological identification,homology was above 97 % among the isolates from these areas with Corynebacterium pseudotuberculosis in GenBank.4.Pathogenicity in Balb/c and dairy goat showed that the isolate was virulent,with characteristic caseous abscess lesions.Whereafter,the isolate was highly sensitive to common antibiotics,such as ciprofloxacin.5.The indirect CLA-diagnostic ELISA showed that the prevalence of caseous lymphadenitis in these areas was as high as 59.92 % in dairy goats.The prevalence of caseous lymphadenitis in Fuping,Long County and Luxi County was 71.50%,67.50% and 25.47%.The prevalence of caseous lymphadenitis under the semi-grazing breeding,newly cooperative management and the intensive management was 25.47%,67.66% and75%.6.According to test of significance,ewes were more susceptible to Corynebacterium pseudotuberculosis infection than animals in other physiological stages.Dairy goats in Luxi County were at less risk of positive than other areas.Dairy goats under the newly cooperative management had a higher risk of CPTB infection than the other management system in this study.Conclusions:1.Corynebacterium pseudotuberculosis was isolated and identified successfully in the main breeding areas of dairy goat in China.2.The results in this study indicate that the prevalence of Corynebacterium pseudotuberculosis infection was considerably increased when detected based on the CLA positive rate of blood samples.