Expression of Toll‐like receptors and host defence peptides in the cecum of chicken challenged with Eimeria tenella

Abstract Chicken coccidiosis, caused by Eimeria protozoa, affects poultry farming. Toll‐like receptors (TLRs) and host defence peptides (HDPs) help host innate immune responses to eliminate invading pathogens, but their roles in Eimeria tenella infection remain poorly understood. Herein, 14‐day‐old chickens were treated orally with 50,000 E. tenella oocysts and the cecum was dissected at different timepoints. mRNA expression of 10 chicken TLRs (chTLRs) and five HDPs was measured by quantitative real‐time PCR. chTLR7 and chTLR15 were upregulated significantly at 3 h post‐infection while other chTLRs were downregulated ( p < .05). chTLR1a, chTLR1b, chTLR2b and chTLR4 peaked at 36 h post‐infection, chTLR3, chTLR5 and chTLR15 peaked at 72 h post‐infection and chTLR21 expression was highest among chTLRs, peaking at 48 h post‐infection ( p < 0.05). For HDPs, cathelicidin (CATH) 1 to 3 and B1 peaked at 48 h post‐infection, liver‐expressed antimicrobial peptide 2 peaked at 96 h post‐infection, and CATH 2 expression was highest among HDPs. CATH2 and CATH3 were markedly upregulated at 3 h post‐infection ( p < .05). The results provide insight into innate immune molecules during E. tenella infection in chicken, and indicate that innate immune responses may mediate resistance to chicken coccidiosis.