Abstract: The attenuated fowl cholera vaccine of strain Clone89 was shown to be safe when administered intramuscularly into layer and broilers of 53 days-12 months old with the doses of 5×10⁹ and 10×10⁹ CFU bacteria respectively. No inflammatory reaction was observed at the injection sites 5 days after administration of 3×10⁷ CFU bacteria. The strain did not renew its virulence, on the contrary, it became less and less virulent after 13 continuous back-passages in chickens with raised doses. No clinical signs from the 7th passage and no local inflammatory reaction from 11th passage were observed, which indicated that no atavism in virulence appears when the bacterine is put into use for Vaccination. One point one million of chickens were vaccinated in field trials. Before the epidemic seasons of the disease, one shot vaccination could control the disease. The clinical sighs calmed down in 2 days and deaths ceased in 3-5 days after early emergency vaccination of infected cholera flocks.

Key words: Fowl cholera, Virulence, Safety, Stability

CLC Number: 

• S852.44