Effect of Zataria multiflora essential oil on immune responses and faecal virus shedding period in broilers immunized with live Newcastle disease vaccines

Zataria multiflora essential oil possesses immunomodulatory effects and the present study investigates its effect on immune responses to live Newcastle disease (ND) vaccines and faecal shedding period of vaccine strain virus in chickens. One hundred and eighty chickens from both sexes were divided into 6 equal groups: group 1: unvaccinated، group 2: vaccinated (B1 vaccine followed by La Sota 10 days later)، group 3: vaccinated + levamisole (150 mg/kg/day، orally)، groups 4، 5 and 6 were vaccinated and received Z. multiflora essential oil by SC injections at 0. 1، 0. 2 and 0. 4 g/kg/day dosages، respectively. Levamisole and Z. multiflora essential oil were administered for 10 and 5 consecutive days post B vaccination. On days 0، 7، 14، 28 and 35 post booster vaccination (PBV)، HI test was performed. Delayed type hypersensitivity (DTH) test was accomplished on day 14 PBV. Faecal virus shedding was determined during 15 days PBV with 3 day intervals by RT-PCR method. Zataria multiflora essential oil induced a dose-dependent increase in antibody titers in an extent higher than levamisole as well as a dose-dependent suppression of DTH reaction. Effect of Z. multiflora essential oil at the dosage of 0. 1 g/kg on shortening of faecal virus shedding period was exactly the same as levamisole where higher doses demonstrated stronger decrease. In conclusion، Z. multiflora essential oil stimulates humoral immune responses and shortens faecal virus shedding period while suppressing cell-mediated immune responses in chickens vaccinated with live ND vaccines