Abstract

The use of the chorioallantoic membrane (CAM) route for the propagation of fowlpox virus (FPV) is the method applied in the production of potent and effective fowlpox vaccine at the National Veterinary Research Institute (NVRI), Vom. However, production insufficiency has led to an inadequate supply of vaccine to meet farmers’ demands. This has left a large number of susceptible and unvaccinated flocks with outbreaks of the disease being reported in Nigeria. This study adapted FPV to Chicken embryo fibroblast (CEF) cell culture and assessed the immunogenicity and safety of the resulting vaccine in comparison to a locally produced CAM-based FPV vaccine. The FPV was propagated on CAM and CEF of 9–12-day-old developing chicken embryos. The vaccine harvests were subjected to quality checks, titrated, and used in vaccinating experimental birds via the wing web to monitor for “takes”, seroconversion, and safety. The FPV was successfully adapted to CEF as demonstrated by the attainment of 80–90% cytopathic effect within 71–115 hours in the different passages. Both the CEF and CAM-adapted vaccine harvests were highly replicative, producing titres of above 106.0/ml TCID50, but higher titres of 108.25/ml TCID50 was recorded in the CEF-adapted vaccines. Experimentally vaccinated birds showed 100% “takes” within 3–4 days post-vaccination, with no adverse effects recorded. This research reported successful development and adaptation of FPV to CEF that was safe and immunogenic, with the potential for its use in the production of a safe and immunogenic vaccine for fowlpox prevention and control in poultry, which may lead to self-sufficiency in fowlpox vaccine production.

Key words: Cell culture adaptation, Chicken embryo fibroblasts, Fowlpox virus vaccine, Immunogenicity, Safety