Abstract

Thermostable Newcastle disease (ND) vaccine virus strain I₂ was investigated for its efficacy as food-borne 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. Pre-challenge 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.

Key words:  Newcastle disease, maize offal, I₂ vaccine, chickens.