Treatment of broiler chickens with the peppermint and eucalyptus essential oils blend improved protection and productive performance as compared with the infected positive control birds. It decreased total mortality, increased final body weight, and decreased final feed conversion ratio (FCR) (P≤0.05). The peppermint and eucalyptus essential oils blend had a positive effect on macroscopic and microscopic lesion scoring and enhanced HI and ELISA titers against Newcastle disease virus vaccine, as compared to their untreated control groups (P≤0.05). In conclusion; the peppermint and eucalyptus essential oils blend used in the present investigation significantly controlled vVND infection where it has immuno-modulatory effect and positively evoked the immune response against this very hot challenging virus which is of great devastating economic impact on poultry industry.

Key words: Broiler chickens, Eucalyptus, Immune response, Peppermint, volatile oils, vVNDV