RESUMEN
1. The effect of Zataria multiflora essential oil on replication rate of the H9N2 virus in target organs was determined by real-time PCR. One-day-old broiler chicks were randomly divided into six groups and were challenged with H9N2 influenza. Two groups received either 20 or 40 µl/kg body weight/day Zataria multiflora essential oils (ZM) seven days before the challenge while two other groups received the essential oil at the same dosage but after H9N2 challenge. One group received 4 mg/kg body weight/day of the anti-viral compound amantadine after challenge and the last group received no treatment and served as the control. 2. Groups that received the ZM, before or after H9N2 challenge, and the amantadine treated group showed reduced viral replication in the respiratory and gastrointestinal tracts compared to the control. Supplementation with ZM improved weight gain and FCR in broilers in comparison with the control. 3. The results showed that ZM had a positive effect on reducing viral replication in both the intestine and trachea of H9N2 influenza infected broiler chickens, that led to milder clinical symptoms and better performance.