Abstract: Chichen Cholera has been threatenning the development of chicken farming seriously.But up to now there are no perfect vaccine to be applied to practice.We have saparated 28 strainsof Pasteurella multocide from the hart blood of chicken died of cholera in our province.Through determining of virulence and immunogenicity we sifted out Sy-8421 as a strain for making vaccine.The strain Sy-8421 possesses the typical character of Pasteurella multocide in organism shape and in culture and biochemical test,and has a good nature of antigen and strong virulence.Two of the strain could cause death of healthful rabbets with two kilogram weight,three to five of this strain could cause death of healthful chicken being six months old.After being cultured in improved Martin’s Bouillo,it was deactivated by 0.3% formaldehyde.Using the white oil No7 as a adjuvant,the Oil-Emulsion Vaccine was produced by emulsifying the culture and adjuvant which were mixed according to certain proportion.The Vaccine was safe,when it was inoculated to healthful chicken being two months old with diploid Imd.and no untoward effect appeared in one week.In la boratory the potency test was made for nine times using 256 chickens.The results were chat the protection rate was 82.4% and the protection time lasted more than six months.The chicken would produce strong immunity after fourteen days of inoculation.Kept in 0-4℃,after 3.5 months,the vaccine would not lose its efficacy and after five months it still maintained its good physical properties.In me-dium examination using thirty thousands chickens,the ideal result was obtained.

Key words: Chicken cholera, Deactivated vaccine, Immunogenicity, potency, Protection time