Evaluation of efficacy of LaSota® vaccine against circulating Newcastle virus strains from Morogoro, Tanzania
Newcastle disease (ND) outbreaks in flocks vaccinated with LaSota® vaccine have been reported around Morogoro municipality. This study was conducted to evaluate the efficacy of commercially available LaSota® vaccine against virulent strains of newcastle disease virus (NDV). One hundred day-old chicks were randomly allocated to five groups of 20 chicks each. Group I and II were vaccinated at the age of 5 days through oral and ocular routes, respectively, and boosted at the age of 20 days. Groups III and IV were vaccinated once through oral and ocular routes, respectively, at the age of 10 days. Group V served as a negative control. Immune response against NDV was measured by the level of antibodies using Haemagglutination Inhibition (HI) test and resistance to challenge with virulent strain of NDV. All birds were challenged with virulent NDV at 32 days of age and monitored for 21 days. Regardless of the route, there was no statistical significant difference (p > 0.05) between the mean HI titres in the four vaccinated groups. Significant differences, however, existed between regimes (p < 0.05). The morbidity and mortality in vaccinated birds were 20% and 10% respectively, while in un-vaccinated birds the corresponding values were 95% and 65%. In conclusion, the used LaSota® strain ND vaccine available in Morogoro, Tanzania produced enough protection against ND. Both oral and ocular routes provided the same level of protection, however, regardless of route of vaccination, booster dose produced higher level of protection.
Keywords: Newcastle disease, oral and ocular routes, layer chicks, vaccination regime, antibodies