Department of Veterinary Microbiology, College of Veterinary and Animal Sciences, G B Pant University of Agriculture and Technology, Pantnagar, 263145 (Uttarakhand), INDIA.
The immune effects of Fowlpox virus (FPV) isolates from field outbreaks, FPV-B07 and FPV-P07 were evaluated in chickens infected at the age of 8 weeks. These strains were adapted to chorio-allantoic memberane (CAM) upto 56 passages and later were propagated and adapted to chicken embryo fibroblast cell-culture by serial passages and used as vaccines in chicken. On 29th day post-vaccination all the birds, vaccinated and control were challenged with virulent strains of FPV. FPV-B07 induced higher level of RPHA titre as well as Neutralization Index (NI) was higher. Interestingly, both strains of attenuated FPV elicited a similar degree of antibody production in inoculated chickens and afforded them protection against a subsequent challenge by a field virus, the origin of which was temporally and geographically similar to that of the progenitor strain. Precipitating antibodies were detected from 7th day onwards in all the groups. Group 1 showed RPHA titre of 1:64 and NI of 1:6 which was higher than that of group 2, 1:32 and 1:45 respectively. Commercial vaccine showed better results with 1:128 RPHA titre and NI of 2.2. Both the groups vaccinated with field strains showed comparatively less protection (71 and 57%, respectively) against the challenge than the group vaccinated with commercial vaccine (100%).
Fowlpox, vaccine, immunogenicity, serology
