Evaluation of avian influenza killed vaccine on tissue distribiution and shedding of avian influenza virus H9N2 in ducklings

Ducks have an outstanding role in the transmission of avian influenza to poultry farms and due to importance of vaccination in reducing shedding the virus, this study was performed to evaluate avian influenza killed vaccine H9N2 on tissue distribution and shedding of avian influenza virus H9N2 in ducklings. One hundred day-old ducklings were purchased and after bleeding from 20 birds, were kept in four separate rooms under standard condition. Groups 1 and 2 were vaccinated at 9 days and groups 2 and 3 were challenged with 0.1 ml of allantoic fluid containing 105 EID50 (A/chicken/Iran/Aid/2013(H9)) virus intra-nasally at 30 days. Group 4 chicks were kept as control group. The chicks were observed two times daily. On days 1, 3, 5 and 8 after inoculation, 3 chicks were randomly selected from each groups and cloaca and trachea swabs samples were collected from each bird. Then the ducklings were euthanized, and trachea, lungs, spleen, intestine, liver and brain tissues samples were collected for molecular detection. The virus was detected in the tissues and tracheal and cloacal swabs by polymerase chain reaction (PCR) and anti-AIV titres were measured by HI test. The results showed no clinical signs in the challenged groups. In vaccinated challenged group, virus was detected only in cloacal swabs but in unvaccinated challenged group, detection of virus in tracheal swabs was more than cloacal swabs. In challenged-unvaccinated chicks, virus was detected in trachea and lungs and in challenged-vaccinated birds, virus was detected in intestine. In conclusion, vaccination of ducks against AI H9N2 virus reduce shedding and tissue distribution of AI viruses in challenged ducks.