Impact of multiple Lasota vaccinations on the haematological parameters of pullets infected with velogenic Newcastle disease virus

Newcastle disease (ND) is an important disease of poultry worldwide. This study aimed to evaluate the impact of multiple ND Lasota vaccinations on haematological parameters of pullets before and after experimental infection with velogenic ND virus (vNDV). A total of 100-day-old chicks were used for the study. They were randomly assigned into five groups, as follows: L1, L2, L3, unvaccinated unchallenged (UU) and unvaccinated challenged (UC). The L1, L2 and L3 were the groups vaccinated once, twice and thrice, respectively, while the UU and UC groups served as negative and positive control groups, respectively. At three weeks of age, birds in groups L1, L2 and L3 were given 0.5 ml of Lasota vaccine orally. At five weeks of age, L2 and L3 were given the second dose. Only the L3 birds were given the third dose at seven weeks of age. Groups L1, L2, L3 and UC were experimentally challenged with 0.2 ml of vNDV intramuscularly at 10 weeks of age. Blood samples were collected from the pullets for haematological evaluations before vaccination commenced (Day 0), and two, four, six and seven weeks post commencement of vaccination (PCoV). Results showed that in all the groups, there was no significant (P>0.05) difference in the packed cell volume (PCV), red blood cell, (RBC), haemoglobin concentration (HBC), total white blood cell (TWBC) and absolute lymphocytic counts on day 0. At weeks two and four, PCoV, TWBC, lymphocyte and heterophils counts were significantly (P<0.05) higher in the vaccinated groups compared to the control. On week six PCoV, L1 had significantly (P<0.05) higher TWBC and heterophil counts compared to L2, L3, UU and UC. It was concluded that vaccinating pullets once with Lasota vaccine was more effective in eliciting a sustainable leukocytic response than vaccinating twice or three times, especially before viral challenge.