Response of chickens to oral vaccination with Newcastle disease virus vaccine strain I2 coated on maize offal
AbstractThermostable Newcastle disease (ND) vaccine virus strain I2 was investigated for its efficacy as foodborne vaccine, using maize offal as the vehicle. Immune response to vaccination and resistance to
challenge were assessed by standard methods. Results showed that following primary vaccination, 40 (64.5%) out of the 62 birds produced detectable haemagglutination inhibiting (HI) antibody, but only 4
(6.5%) produced HI (log2) antibody titre 3.0 regarded as protective with a geometric mean titre (GMT) of 3.1. After a booster dose, 49 (79.0%) seroconverted and 20 (32.3%) had HI (log2) titres 3.0 with GMT of 4.9. When challenged all vaccinated birds survived while all control (unvaccinated) birds died. Prechallenge HI antibody titre of 50 vaccinated birds selected for challenge showed that 13 (26.0%) had titres 3.0 and GMT = 4.5, while post-challenge, 31 (62.0%) had HI (log2) 3.0 with GMT of 7.2. Using Student t test analysis of significance, the birds were observed to show 70% HI antibody production at a P 0.3 and 3 degree of freedom (df), and 70% secondary immune response on challenge at 4df. It is therefore concluded that the vaccine could be effective for protection of village chickens as food-borne vaccine provided the carrier foods are adequately treated.