Efficacy of Inactivated H9N2 Avian Influenza Vaccine against Non-highly Pathogenic A/Chicken/Iran/ZMT-173/1999 Infection

Abstract

Summary An experimental avian influenza (AI) oil-emulsion vaccine was formulated with a ratio of 4 parts oil adjuvant ISA-70 and 1 part formalin inactivated A/Chicken/Iran/ZMT-101(101)/98(H9N2) antigen. Thirty 2-week-old Aryan broilers and thirty 2-week-old white Hy-line pullets were vaccinated subcutaneously. The latter was delivered a booster 10 weeks after primary vaccination. All vaccinated and control birds were bled for hemagglutination-inhibition (HI) test at least one week intervals. Half of the birds were challenged via intranasal and intravenous routes with a H9N2 strain at 8 and 27 weeks of age in broiler and layer birds, respectively. A high HI titers were observed in both vaccinated and unvaccinated birds, when examined at 2 weeks postchallenge (PC). Viral isolation or shedding from tracheal and cloacal swaps of both vaccinated broiler and layer was decreased at 2 weeks PC, as compared with unvaccinated control birds. All control birds became morbid, and egg production decreased on day 3 PC. The results suggested that the inactivated oil-emulsion H9N2 AI vaccine may be protects both chickens against viral shedding and egg drop in field conditions.