Evaluation of Alum Precipitated Formalin Killed
Fowl Cholera Vaccines with Their Immunologic Responses in Ducks
The alum precipitated formalin killed fowl cholera vaccines (FCV) are locally produced from the Livestock Research Institute (LRI), Mohakhali, Dhaka and Bangladesh Agricultural University (BAU), Mymensingh which are being used to control fowl cholera in chickens and ducks in Bangladesh. Efficacy of these two vaccines has been evaluated mostly in chickens but reports on ducks are very limited. Four weeks old 50 Jinding breed of ducks were used to evaluate the efficacy and immune responses of fowl cholera vaccines during the period from October 2002 to March 2003. These 50 ducks were divided into three groups (A = 20, B = 20 & C = 10 ducks) and each duck of group A was inoculated with FCV (LRI) @ 0.5 ml subcutaneously at the age of 8 weeks, and each duck of group B received FCV (BAU) @ 1.0 ml intramuscularly at the age of 12 weeks as manufacturer instruction, whereas ducks of group C served as unvaccinated control. Each duck of group A and B was also injected booster dose after two weeks of primary vaccination with their respective FCV. Each duck of all the three groups (A, B and C) was challenged after two weeks of post-booster vaccination with 1.0 ml inoculum containing 5.4x106 CFU of virulent Pasteurella multocida intramuscularly. The results of challenged experiment revealed that one (5.0%) duck of group A, two (10.0%) ducks of group B died within 2 to 3 days of post-challenged, whereas 10 (100%) unvaccinated control ducks of group C died within 1 to 3 days of post-challenged. Therefore, the FCV® (LRI) conferred protection to 95% and FCV (BAU) conferred protection to 90% of vaccinated birds against challenged infection after two weeks of booster vaccination. The mean values of Total leukocytic count (TLC), Total serum protein (TSP) and Passive haemagglutination assay (PHA) antibody titre of ducks in both the groups A and B were found significantly (p < 0.01) increased at two weeks of post-primary and two weeks of post-booster vaccination, and also two weeks of post-challenged infection in comparison to the respective pre-vaccination values. These results indicate that the FCV of LRI induced comparatively higher TLC, TSP and PHA antibody titre than FCV of BAU in ducks. These results showed that the locally prepared fowl cholera vaccines induced sufficient cellular and humoral immune responses which resulted satisfactory level of protection against duck cholera and therefore both the locally prepared FCV could be recommended to control duck cholera under filed conditions in Bangladesh.
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