Evaluation of immunization with infectious laryngotracheitis vaccine in White Bovans and HyLine W36 pullets

Infectious laryngotracheitis (ILT) is an acute viral respiratory tract of chickens with worldwide outbreak, and its virus latency, presence of carrier chickens, and long-term virus separation have been increased the difficulty of ILT control. Because of considerable economic losses associated with ILT, vaccination of susceptible pullets with attenuated viruses is recommended in endemic areas. The aim of the present study was to compare the immunization of ILT vaccine produced by Razi Vaccine and Serum Research Institute in White Bovans and HyLine W36 pullets. Seventy thousand pullets of each laying line were allotted into two different farms and were vaccinated with Razi ILT vaccine through eye drop method at eight week of age. In order to determine sera antibody titers against ILT virus by ELISA and serum virus neutralization tests, blood samples were randomly collected from 20 chickens per group before (d=0), and at 3, 6, 8, 10, 12, and 16 weeks post-vaccination. In addition, three weeks following vaccination, 20 birds per group were challenged with a nasal drop of virulent infectious laryngotracheitis (vILT) virus strain to evaluate vaccine effecacy. Results showed that Razi ILT vaccine caused a similar performance regarding serological ELISA antibody titers against ILT and the virus neutralization index in the both strains (P > 0.05). Trends in ELISA antibody tiers against ILT and the virus neutralization index revealed that these incidies reached to the protective immunity threshold three weeks post-vaccination. Moreover, Razi ILT vaccine was effectively protected 100% and 95% of White Bovans and HyLine W36 pullets against a vILT challenge, respectively. In conclusion, vaccination of White Bovans and HyLine W36 pullets with Razi ILT vaccine produced sufficient sera titers against ILT, resulted in effective immune protection against vILT virus. However, there was no difference between White Bovans and HyLine W36 pullets regarding the evaluated immune insides following vaccination.