Evaluation of the safety and efficacy of combined Newcastle disease, fowl pox and fowl typhoid vaccine under laboratory condition

An experimental study was conducted on day-old chicks to evaluate the safety and efficacy of combined Newcastle diseases (ND), fowl pox (FP) and fowl typhoid (FT) vaccine. The vaccine was prepared using the Lasota strain of Newcastle disease virus (NDV), the FP strain of fowl pox virus (FPV) and the 9R strain of FT. The vaccine was found safe, as no clinical signs or mortalities were observed. Post vaccination Haemaglutination Inhibition (HI) titre for ND was above the required protection level (≥1:16) and its geometric means (GM) were 0.0098, 0.0063 and 0.0059 for group one, two and three respectively, who received conventional and combined vaccine. The difference in GM between the three vaccinated groups were not significant (p=0.544). The trivalent combined vaccine did not show significant difference in the HI titre result among the groups that were given conventional vaccines and the other two experimental groups which received trivalent vaccine (p=0.257). From 75 samples, 73 (97.3%) were positive for FT through rapid slide agglutination test (RSAT). The chicks were challenged separately for the three diseases using the specific pathogens. Both combined and conventional vaccine conferred protection upon challenge. For ND challenge, 93.3% (n=14/15) of the control groups died. From FT and FP control groups 86.6% (n=13/15) and 20% (n=3/15) respectively died up on challenge. Both combined and conventional vaccine type conferred a similar and good level of protection. However, the use of combined vaccine has considerable advantage particularly in terms of convenience and cost effectiveness to control multiple diseases through simple immunization schedule. Further studies were recommended on the development of combined avian vaccines in Ethiopia.