Evaluation of two vaccination schemes using live vaccines against newcastle disease in chickens

The use of different types of Newcastle disease (ND) vaccine in different vaccination schemes has decreased the incidence of velogenic Newcastle disease (VND) in commercial poultry worldwide. In under-developed countries like Pakistan, these vaccination schemes are not successful due to free-range and backyard poultry production. This trial was conducted in 90 experimental chickens to develop an effective control against ND. The level of antibody response, detected by haemagglutination-inhibition (HI) test, and the degree of protection against the virulent strain of Newcastle disease virus (NDV) were studied. The chickens were immunized with commercially available ND vaccines. In scheme A, primary vaccination was done with La Sota vaccine with 109 EID50, administered on day 5 by eye drop (E/D), followed by a booster vaccination with the same vaccine and the same route on day 21 and, in scheme B, primary vaccination was done with the same vaccine (La Sota vaccine with 109 EID50), administered on day 5 by E/D, followed by a booster vaccination with a mesogenic strain (Mukteshwar) given intramuscularly on day 21. Both schemes of immunization conducted ensure comparatively solid immunity when challenged with a virulent field isolate of ND at 6 weeks of age. A better protection index was obtained from chickens vaccinated with scheme B.