Abstract

Strategic control of canine rabies amongst the domestic dog population in endemic regions requires the use of wholesome and potent rabies vaccine, together with strict adherence to a regimented vaccination programme, geared towards eradication. In this study, we applied the Direct Fluorescent Antibody Test (DFAT) to determine Tissue Culture Infectivity Dose50 (TCID50) potency values of five batches of dog anti-rabies vaccine produced at the National Veterinary Research Institute (NVRI), Vom, Nigeria. This was carried out after infecting suspension of Baby Hamster Kidney (BHK-21) cells at a concentration of 3.0 × 105 cells per mL in 96-well microtitre plates. Consequently, 100µL of serially diluted anti-rabies vaccine was dispensed in each well and incubated at 37℃ in 5% carbon dioxide condition for three days. On the fourth day, the TCID50 potency values of the vaccines were determined as log10 TCID50 5.6; log10 TCID50 3.5; log10 TCID50 5.5; log10 TCID50 4.2, and log10 TCID50 5.5 per dose, respectively, against the standard reference titre value of log10 TCID50 3.0 per dose. Our findings revealed that DFAT is reliable, rapid, and drastically reduces the time duration for TCID50 potency value determination to 96 hours. Application of DFAT enables handling of multiple batches of anti-rabies vaccine concurrently and determining their TCID50 per dose value simultaneously. To our knowledge, this is the first multiple assay of rabies vaccine batches in Nigeria using the DFAT. Furthermore, our study attests to the robust nature of the NVRI anti-rabies vaccine. The DFAT should be widely utilized for the rapid determination of anti-rabies vaccine TCID50 potency value.

Key words: Direct Fluorescent Antibody Test, Rabies Vaccine, Tissue Culture, TCID50, Nigeria