الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 165 |  |  |
| | | from | 165 | | |
Abstract
The present study was designed to evaluate the effect of carvacrol essential oil on early immune response, viral shedding titer, leucogram, oxidative stress, serum biochemical parameters, histopathology of trachea, lung and kidney and clinical consequences in broiler chickens experimentally infected by infectious bronchitis virus (IBV). One hundred and twenty-one-day old commercial broiler chicks were equally divided into 4 groups:
First group (control): birds were non-treated with carvacrol and non-infected with IBV.
Second group (CA.oil): birds were orally given carvacrol (250 µl/bird) 3 times/week for the first three weeks of age (5th-7th, 12th-14th and 18th-20th days).
Third group (IB): birds were infected with 106 EID50/0.5 ml of titrated IBV using intra-tracheal route at the 22nd day old.
Fourth group (CA.oil+IB): birds were orally given carvacrol and infected with IBV as previously mentioned doses.
The birds were noticed daily for clinical signs and mortalities for 10 days after challenge. Tracheal swabs were collected at the 2nd, 5th, 7th and 10th DPI for detection of virus shedding from infected groups. Blood samples were collected from wing vein at the 2nd, 5th and 7th and 10th DPI for hematological, biochemical and immunological assays.
Hematological assays included total and differential leucocytic counts and H/L ratio, while biochemical parameters includes serum concentrations of uric acid, creatinine, Na, K, P, Ca, Mg. Immunological parameters included IL-6, α1-AGP and antibody titer against IBV in the serum.
The organs including trachea, lung and kidney were collected for histopathological examination and oxidant /antioxidant biomarkers estimation in lung and kidney (including MDA content, SOD activity and GSH content). Besides, the estimation of chIFITM3 gene expression level in trachea.
In comparison with the mean values of control group, the following results were observed.
group (CA.oil): at the 2nd and 5th DPI, there were significant decrease in H/L ratio, serum IL-6 and α1-AGP concentrations and gene expression level of chIFITM3 in trachea. As well as a significant reduction in heterophil number at the 5th DPI. At the 7th DPI, results showed significant reduction in heterophil number and H/L ratio.
group (IB): at the 2nd DPI, there were significant increases in TLC, lymphocyte, heterophil, monocyte and eosinophil numbers, H/L ratio and the serum concentrations of IL-6, α1-AGP and P. The MDA level was significantly increased and SOD activity reduced in lung. As well as elevation the gene expression level of chIFITM3 in trachea. At the 5th DPI, IBV infection significantly elevated TLC, lymphocyte, heterophil, monocyte and eosinophil numbers, H/L ratio and the serum concentrations of IL-6, α1-AGP, uric acid, creatinine with reduction of Na level. As well as elevation the gene expression level of chIFITM3 in trachea. There was significant elevation on MDA level and reduction in SOD activity in both lung and kidney. At the 7th DPI, results revealed significant increases in TLC, lymphocyte, heterophil, monocyte and eosinophil numbers, H/L ratio and the serum concentrations of uric acid and creatinine with reduction of Na level. The MDA level was significantly increased, SOD activity significantly reduced in both lung and kidney and the GSH content significantly decreased in kidney. At the 10th DPI, antibody titer against IBV significantly elevated.
group (IB+CA.oil): at the 2nd DPI, there were significant increases in TLC, lymphocyte, heterophil and monocyte numbers, H/L ratio and the serum concentrations of IL-6 and α1-AGP. The SOD activity significantly reduced in lung. As well as elevation the gene expression level of chIFITM3 in trachea. At the 5th DPI, results showed significant increases in TLC, lymphocyte, heterophil, monocyte and eosinophil numbers, H/L ratio and the serum concentrations of IL-6, α1-AGP, uric acid and creatinine. As well as elevation the gene expression level of chIFITM3 in trachea. The MDA level was significantly increased and SOD activity significantly reduced in lung. At the 7th DPI, there were significant elevations in TLC, lymphocyte, heterophil, monocyte and eosinophil numbers, H/L ratio and the serum concentrations of uric acid and creatinine. The MDA level was significantly increased and SOD activity significantly reduced in lung. At the 10th DPI, there was significant elevation in antibody titer against IBV.
On the other hand, in comparison to IB group, there were significant decreases in TLC, heterophil, eosinophil numbers and H/L ratio along the experimental period. The serum concentrations of IL-6, α1-AGP and uric acid and the antibody titer against IBV were significantly reduced with elevation of Na level. The MDA level significantly reduced in lung at the 2nd DPI and in kidney at the 5th and 7th DPI. In kidney, the SOD activity significantly elevated at the 2nd, 5th, 7th DPI, while GSH content significantly elevated only at the 7th DPI. Furthermore, the shedding titer of IBV and gene expression level of chIFITM3 in trachea were markedly reduced.
Histopathological changes:
The infection with IBV showed tracheitis (loss of cilia, mononuclear cell infiltration of lamina propria and mucosal thickening), parabronchitis (loss of cilia, and the lamina propria and peri-bronchial space infiltration with heterophils and mononuclear cells) and interstitial nephritis (mononuclear cell infiltration in the intertubular spaces, variable degree of congestion and edema, necrosis and desquamation of the renal tubular epithelium).
In CA.oil+IB group, carvacrol administration lessened the histopathological changes caused by IBV infection with the minimal effect on lung tissue.
Conclusion:
from the present study it is concluded that
1) Infection with IBV in broiler chicken induced elevation in TLC, H/L ratio, serum concentrations of IL-6 and α1-AGP. As well as increment the oxidative stress in lung and kidney and upregulation of the chIFITM3 gene expression in trachea
2) The carvacrol essential oil administration before IBV challenge had a positive impact on early immune response of the birds through reduction of serum concentrations of IL-6 and α1-AGP.
3) The carvacrol effectively diminished H/L ratio, improved the oxidative status and histopathological picture induced by infection (with least effect on lung) and reduced the tracheal viral shedding titers via inhibition of viral replication.
4) The field application of carvacrol essential oils with the commercially available vaccines could be useful in IB control through improvement current immunization strategy, potentiation of bird immune response against IBV and other viral respiratory diseases and enhancement the recovery from infection.