Epidemiologic Investigation And Primary Immunologic Test Of Cattle Escherichia Coli Diarrhea In Shaanxi Province

Calf diarrhea was a gastrointestinal disease to 1-month-old calves with dyspepsia, diarrhea as the main symptoms, and multiple to 4~10 days of age. Infected calves mainly character with hyperthermia, diarrhea, dehydration, autotoxin and cardiac failure, it was the one of main pestilence caused calves dead. There were many causes to calf diarrhea, but Escherichia coli were the first cause among the pathogenic bacteria, which had brought huge economic losses in cattle industry. E. coli has complex serotypes and antigen, the toxicity of its enterotoxin was not certainted, and the serotypes were very different in every endemic area. So, investigating epidemiologic of calf diarrhea, identificated the toxicity and advantages serotype, and developed an operative inactivated vaccine in accordance with these, have more practical significance to control this disease.This paper has investigated epidemiologic of the calf diarrhea with 12 farms and part of farmers in five cities in Shaanxi province from Sep. 2005 to Sep. 2007, and proved that pathogenic E. coli was the main pathogen. The investigation results showed that the disease has higher morbidity rate (19.47%) and mortality rate (47.51%) in these areas; the disease occurred in every season and has a highest morbidity rate (18.87% and 21.26%) from Dec. to Apr.; it mainly infected calves within 1 month old and has a highest morbidity rate (30.27%) and mortality rate (54.73%) within 10 days of age.The detection results of enterotoxin in isolated bacteria showed that, there were 23 isolates can secrete ST and 21 can secrete LT. The identification test of serotypes proved that there were 12 serotypes such as O2,O8,O9,O20,O55,O64,O75,O78,O86,O101,O138 and O141, and O2,O86,O101 were advantages serotypes which have stronger toxicity. There were many serotypes in different areas and different farms or famers in same area, even in same farm. So this can lay the etiology foundation for control bacterial diarrhea in this area.The results of sensitive experiment to isolate showed that NOR, GEN, CFP, AMI and KAN were extremely sensitive; AMP, SXT, ERY were lowly sensitive. This can caused by using these drugs in a long term or in a large scale, and made pathogens drug-resistant. Chinese herb Honeysuckle and Dendranthema Flower were extremely sensitive to isolate. So we took them as basic remedy and developed prescription"Changjunqing Powder". The powder had an obvious bacteriostasis to isolated bacteria and its total effective percentage was 88.9% in the clinical trial to typical case of calf diarrhea.Selected 3 advantages serotype pathogenic E. coli strains, polyvalent oil-adjuvant inactivated vaccine and aluminum hydroxide gel vaccine were prepared. The sterility, security test and valence of antibody, protection detection indicated that the developed inactivated vaccine had good protection.