Lesion Observation And Pathogenicity Of Tested Tuberculosis Positive Cattle

From march and December,2016 to July,2017,three stocks of 2000 dairy farms were quarantined for tuberculosis positive farms in Xinjiang autonomous region by three times.The positive dairy cattle were culled.As tuberculosis positive cattle were always emerge and most of the cattle were young cattle that weren’t introduced from other farms in the period,thus,we infer the new positive cattle were infected by other positive cattle in the same farm.For this reason,lesion characteristics,transmission and pathogenic characteristics were carried out in our research.The purpose of this study was to observe the ophthalmological lesion and histopatholy by autopsied positive cattle for revealing the lesion range and pathological features of bovine tuberculosis;Collecting sample from culling positive cattle and isolating tubercle bacillus,the pathogenicity characteristics and propagation path were studied through animal test;Building absolute fluorescence quantitative polymerase chain reaction(PCR)on mycobacterium tuberculosis complex and mycobacterium bovis were used to detect milk and feces samples for exploring the route of transmission of dairy cow tuberculosis.Through necropsy showed that there were 37 cows occurred tuberculosis lesions in the mesenteric lymph nodes among the 65 cows,followed by hilar lymph nodes and liver,but only 8 were present in the lungs.Collectting various organs and tissues by histopathological examination confirmed that tuberculosis lesions were widely distributed in extrapulmonary tissues,especially mesenteric lymph nodes.Tubercle bacillus were detected by established detection method of a rapid and accurate absolute fluorescence quantitative PCR from milk and fecal samples of negative cows and mixed milk and feces samples showed that there is a risk of infection on dairy farms.Through identification of separated 38 strains bacteria,caused bovine tuberculosis pathogen mainly is m.bovis.Although mycobacterium tuberculosis only accounted for 3 strains,but there are some hidden dangers to the cattle ranchers and food safety.The results of rabbit symptoms and necropsy,HE staining,acid-fast staining and bacterial content test showed that vaccinated rabbits by intraperitoneal injection and oral administration had no respiratory symptoms,however,the rabbits in nasal drops had respiratory symptoms.All the rabbits only had emaciation and weight loss.Infected the rabbits by intraperitoneal injection and orally were mainly in mesenteric lymph nodes andhilar lymph nodes,followed by liver and spleen,and the lungs had less lesions.It is consistent with the lesion distribution of the culled positive cattle.But by the nasal drops had lesions in the lungs and fewer rabbits occurd lesions,whith is different from them.It was verified that the cows infected with tuberculosis passed through the digestive tract.This study concluded that in three dairies the positive bovines by tested tuberculous are mainly young cows,and their lesions were located in extrapulmonary organization,especially the mesenteric lymph nodes,pathogens caused bovine tuberculosis were mainly mycobacterium bovis;The occurrence of bovine tuberculosis was mainly related to the infection of mycobacterium bovis through digestive tract,and the study provides a new theoretical basis for the purification of bovine tuberculosis.;Tuberculous bacteria were detected in milk and feces of negative cattle and mixed milk and feces collected from quarantine positive cattle farms,and this can reveal the reason why the quarantined and purified cattle are constantly showing new positive cattle.