Efficacy of live oil adjuvanted Lasota strain newcastle disease vaccine in broiler chicks under experimental conditions

The present study was conducted to compare the efficacy of lives in-oil ND vaccine with live and killed-in-oil ND vaccines. The experimental OE vaccines were prepared using the ND virus strain (LaSota) and aqueous to oil ratio 1:4: The hydrophile balance (111B) was fixed at 7.0 using surfactants (Tween-80 and span-80). The physical properties (appearance, viscosity, emulsion type and stability) were noted. A total of 120 day-old broiler chicks were taken and divided into 6 groups A, B, C, D, E and F each having 20 chicks. At the age of 7 days, birds of groups A, B, C and D were vaccinated against ND with live commercial, formalin killed-in-oil, live-in-oil with half antigen dose and live-in-oil with single antigen dose respectively while the group E was inoculated with only the oil adjuvant and the group F was kept as non-vaccinated control. Efficacy of the vaccines was evaluated-on the basis of the humoral immune response and protection against challenge. All the three experimental OE vaccines had same viscosity (7 seconds). All the vaccines had the stability for more than 4 weeks at 4 centigrade more than 9 weeks at 37 centigrade at room temperature. Serum samples were collected at weekly interval from day Zero to day 42 and tested against Newcastle disease virus antibodies by haemagglutination inhibition test. On 14 days post- vaccination (21 days of age) challenge with the velogenic field ND virus was given to 10 birds, of each group. The six weeks cumulative mean titres (CMT) of the four experimental vaccines ranged from 45 to 79. Highest CMT was shown by live- in-oil with full antigen dose vaccines (79) followed by live-in-oil vaccine with half antigen dose vaccine (72) live commercial vaccine (47) and killed-in-oil vaccine (45). The analysis of the data showed that the HI antibody titres against Newcastle disease between the group E and F were not differing significantly. The HI antibody titres of group A and B were significantly higher than the group E and F. The III between the group were different non-significantly. The difference of III titres between D and C groups was not significantly higher than groups A, B, E and F. The HI-titres of groups B and A were significantly lower than the titres in groups C and D. The HI titres between group 1) and C were not differing significantly but the titres of group D were relatively higher than C. The peak antibody titres against Newcastle disease in groups A, B, C, D, E and F respectively were observed on 14, 21-28, 28-35, 28-35, 0 and 0 days post vaccination. All the experimental OE vaccines gave 70-90 percent protection against challenge exposure with velogenic viscerotropic NDV. The highest protection was shown by group D vaccinated with live in oil with single antigen dose and control groups showed the lowest protection (10 percent)