Assessment of Quercetin and Thyme Oil Effect on Oxidative Stress Biomarkers and mRNA Expressions of Interleukin 6, 2, and 16 During Eimeria tenella Infection.

Coccidiosis is a protozoan disease that causes serious economic losses annually worldwide. This study evaluated thyme oil and quercetin as natural anticoccidial treatments in broiler chickens experimentally infected with Eimeria tenella. In total, 450 one-day-old Hubbard broiler chicks were allocated into 10 groups. On the eighth day of age, five groups remained uninfected: a negative control group (-ve) and early-treated and late-treated groups treated with thyme oil or quercetin. The other five groups were infected with E. tenella: a positive control group (+ve) and early-treated and late-treated groups treated with thyme oil or quercetin. The clinical signs, parasitologic findings, oxidative stress biomarkers, and the relative expressions of interleukins 2, 6, and 16 were evaluated on the sixth, 11th, and 16th days postinfection (dpi). The infection induced bloody diarrhea, weight loss, and high lesion scores in +ve controls, while the infected, thymol-treated (ITE) group yielded the best clinical recovery, lowest lesion scores, and highest weight gain among infected groups. Oocyst shedding peaked at 8 dpi but was significantly reduced in early-treated groups, particularly ITE. Oxidative stress biomarkers and interleukin relative expressions were significantly altered, with early treatment improving antioxidant status and modulating immune responses. In conclusion, the results recommend the early administration of either thyme oil or quercetin to improve the productivity, oxidative stress, and birds' immune response against Eimeria infection.