Study of CU strain Pasteurella multocida for duck cholera vaccine

Abstract

The growth study of Pasteurella multocida : CU strain in 3 media showed that the organism grew in brain heart infusion (BHI) broth better than in tryptose broth with thiamine and it died in flesh-liver duck broth. The growth study of this bacteria in BHI broth when it was incubated in various conditions appeared that the growth at 37℃ shaking 200 rpm was the best and the growth decreased at 41.5℃ static and 41.5℃ shaking 200 rpm respectively. The starting bacteria of about 106 CFU/ml incubated in static or shaken condition reach maximal viable cells during 6-9 hr and maximal turbidity in 12 hr after that both of them were constant throughout the incubation period of 48 hr The number of viable cells in 6 hr and 9 hr was so different in the incubation at 37℃ static condition unlikely to that in shaken condition. The virulence study of P.multocida : CU strain in ducks which were subcutaneously (S/C) inoculated at the age of 1,2,3 and 4 wk revealed that all 1-wk-old ducks of each inoculated with 1.6x109 CFU died and 2-wk-old, 3-wk old, 4-wk old ducks, 16 of 20 ducks, 12 of 20 ducks and 1 of 20 ducks died following the inoculation of 3.77x109,1.8x109 and 1.6x109 CFU per duck, respectively. The degree of protection in 1,2,4 and 8 wk after the first vaccination was -15, 56, 88 and 60 in S/C vaccinated group; 35, 46, 32 and 10 in oral vaccinated group and 25, 26, -12, and 20 in drinking water vaccinated group. For double vaccination of 1 month interval high level of protection (not less than 80%) was observed through 8 wk except the drinking water vaccinated group which the percentage of protection was 89, 68, 50 and 48 in 1, 2, 4 and 8 wk after the second vaccination. The percentage of protection in 4 wk after the second vaccination of double vaccination of 2 months interval was 71, 65 and 83% respectively, in S/C, oral and drinking water vaccinated group. However 30% and 20% death occurred in S/C vaccinated group after the first vaccination and the second vaccination in 1 month interval whereas only 2% death occurred in oral vaccinated group after the first vaccination. TA titers and PHA titers of S/C vaccinated group were higher than the other two groups. The antibody levels against antigen of the 8:A strain was higher than those against antigen of the CU strain. The PHA titers of S/C vaccinated group peaked in 1 wk after each vaccination. However those of oral and drinking water vaccinated group were very low especially the GMT detected by the CU sonicated antigen was mostly lower than 2.00.