COMPARATIVE EFFICACY OF FIVE DIFFERENT BRANDS OF COMMERCIAL NEWCASTLE DISEASE LASOTA VIRUS VACCINES IN BROILERS

T. ABBAS, M. A. MUNEER, M. D. AHMED, M. A. KHAN, M. YOUNUS AND I. KHAN

University of Veterinary and Animal Sciences, Lahore, Pakistan

Abstract

    Five commercial LaSota strain Newcastle disease (ND) vaccines namely A, B, C, D and E were evaluated for their potency, efficacy, thermostability and influence on productivity in broilers. A 3-log₁₀ difference of EID₅₀ and two-to-eight fold difference of HA activity was found among the various vaccines tested. One hundred and fifty day-old broiler chicks were divided into six equal groups tagged as I, II, III, IV, V and VI. The birds in groups I, II, III, IV and V were actively immunized against ND on days 7 (eye drop method) and 21 (drinking water) using vaccines A, B, C, D and E, respectively. The birds in group VI served as unvaccinated control. The serum HI antibody response to five vaccines was determined 7, 14, 21 and 28 days post-vaccination. Fifteen birds from each group including unvaccinated control were challenged at day 35 with local virulent ND field isolate. The HI serum antibody profile and post-challenge mortality pattern revealed a dose-response relation between the virus content, humoral antibody response and clinical protection. To compare the heat stability, the vaccines were incubated at 4, 25 and 40⁰C for a period of 24 hours. There was no remarkable reduction in HA titer, however slight dips (less than 2 logarithmic units) in EID₅₀ values were found in all the vaccines. All the vaccines caused significant suppression in weight gain, leading to a poor performance in terms of feed conversion ratio (FCR) and European Efficiency Factor (EEF).

Key words: Newcastle disease, LaSota virus, vaccine, potency, efficacy, thermostability, broilers.