Effect of dose and time of vaccination on immune response of duck plague vaccine in ducks

Effect of dose and time of vaccination on immune response of duck plague vaccine in 90 (45 of 18-day-old and 45 of 35-day-old) Jinding ducklings was studied during the period from October 2002 to March 2003. Each of both age group (18-day-old and 35-day-old) was divided into three groups as A, B, C and D, E, F respectively, consisting of 15 ducklings in each. Each duckling of groups A and B was primarily vaccinated with 0.25 ml and 0.5 ml of duck plague vaccine (LRI, Mohakhali) intramuscularly at 18 days old respectively and could not be boosted due to the death of all the ducklings of both groups within 20 days of primary vaccination. Each duckling of group D and E received 0.5 ml and 1.0 ml of duck plague vaccine (LRI, Mohakhali) intramuscularly at 35 days old respectively and ducks of both the groups boosted with 1.0 ml of vaccine 5 months after primary vaccination. Groups C and F served as unvaccinated control. 14 days after booster vaccination ducks of group D, E and F were challenged with the virulent field isolate of duck plague virus @ 1.0 ml / duck IM (104 EID50 / dose). The ducklings of group D that were vaccinated primarily at 35 days old with 0.5 ml and boosted after 5 months with 1.0 ml of duck plague vaccine had significantly (p< 0.01) higher PHA titres after 2 weeks of primary vaccination (38.4 ± 6.4), booster vaccination (153.6 ± 25.6) and challenge infection (281.6 ± 62.71) in comparison to control group (≤4, ≤4 and 20.0 ± 2.3 respectively) and all the ducks survived (100%) after challenge. The ducklings of group E that were vaccinated primarily at 35 days old and boosted after 5 months of primary vaccination with 1.0 ml of duck plague vaccine had also significantly (p< 0.01) higher PHA titres after two weeks of booster vaccination (76.8 ± 12.8) and challenge infection (153.6 ± 25.6) in comparison to control group, but only 8 (53.3%) ducks could protect the challenge infection with virulent duck plague virus. It may be concluded that ducklings below 30 days of age should not be vaccinated with duck plague vaccine. It also may be proposed that primary vaccination at 35 days old with duck plague vaccine (LRI, Mohakhali) @ 0.5 ml / duckling and booster vaccination after 5 months of primary vaccination @ 1.0 ml could be practiced for better immune response against duck plague.Key words: effect; dose; age; immune response; duck plague vaccine; ducksdoi: 10.3329/bjvm.v2i2.2542Bangl. J. Vet. Med. (2004). 2 (2): 117-119