Abstract:
Two oil emuisified vaccines of Newcaslte disease were prepared from Lasota strain. The virus was propagated in 9-day-old chicken embryos through allantoic route. The haemagglutination titre of the allantoic fluid used for vaccine preparation was 2048. The fluid was inactivated by 0.1 per cent f nal concentration of formalin at 37 oc for 6 hours. Inactivated allantoic fluid was emulsified with aqueous to oil (mineral oil) ratio of 1:2 (vaccine I) and 1:4 (vaccine II). The hydrophile-lipophile balance (HLB) of the vaccines was fixed at 7.0 using oil phase (Span 80) and aqueous phase (Tween 80) surfactants. Physical characteristics including colour, viscosity, stability and type of emulsion were studied. Sterility and safety were tested. Efficacy of the vaccine was evaluated on the basis of humoral antibody response and post challenge protection in layer chicks. One hundred and twenty, 4-week-old-layer, chicks were divided into 4 groups (A to D) comprising 30 birds each. Group A and B were injected with two experimental vaccines, C with imported oil emulsion vaccine and group D was kept as non-vaccinated control. Statistical analysis showed non-significant differen ce among four weeks cumulative haemagglutination inhibition mean titres of vaccine-I (256), vaccine-II (243) and imported vaccine (217). All the three vaccinated groups showed significantly higher titres than those of non-vaccinated control group. Both the experimental and imported vaccines gave 80 per cent protection against challenge with field virulent virus at 4 weeks post-vaccination.
