A comparative evaluation of the immunogenicity of cell culture adapted Fowl Pox vaccines.

Fowl Pox (FP) is a globally important avian disease with no standardized treatment, thus vaccination remains the most effective strategy for the prevention and control of the disease. Fowl Pox vaccines in most countries are propagated on chorioallantoic membrane (CAM), but the use of cell cultures which is more economical, productive and immunogenic has found widespread application in modern veterinary vaccinology, but not in Nigeria. Thus, the need for Nigeria to align with the global best practices in the search of FP virus vaccines that is highly infectious and immunogenic. This study evaluated and compared the immunogenicity of various cell culture adapted vaccines. Fowl pox virus (vaccine seed) was propagated in Vero cells, chicken embryo fibroblast (CEF), duck embryo fibroblast (DEF) and quail embryo fibroblast (QEF) and harvested after attaining 80-90% cytopathic effect, and subjected to sterility tests using Tryptose Soya broth and Thioglycolate medium. The Tissue Culture Infective Dose (TCID50/mL) were calculated using Spearman-Kärber formula. Pre -and- post vaccination antibody levels were analysed using Agar Gel Immunodiffusion test and Enzyme Linked Immunosorbent Assay respectively. The study demonstrated that FP vaccines produced in various suspension cell culture were sterile and immunogenic, with titres as follows: CEF = 109.3 TCID50/mL, QEF = 108.6 TCID50/mL, DEF = 107.6 TCID50/mL, and Vero = 107.3 TCID50/mL. Birds developed “takes” within 7 days post-vaccination (PV) and high level of serum antibodies was also induced PV. Further studies is required to determine the longevity of the induced antibodies and when booster doses should administered.