Foot pad dermatitis in growing turkeys is associated with cytokine and cellular changes indicative of an inflammatory immune response.

Cell and cytokine responses during the development of foot pad dermatitis (FPD) in growing turkeys were studied in a model system. The objective was to evaluate the hypothesis that FPD is an allergic response to the environmental materials. Hybrid female turkeys at 28 days of age were exposed to wet litter for 48 h in a randomized block experiment. Expression levels of pro-inflammatory (interleukin (IL)-1 beta, IL-6, and CXCLi2) and signature Th1 (interferon-gamma), Th2 (IL-13) and Treg (IL-10) cytokines were measured in the foot pad tissues using real-time quantitative reverse transcriptase-polymerase chain reaction. Sections of foot pad tissue were stained for CD4+ and CD8+ T lymphocytes, B lymphocytes and macrophages using antibodies that specifically recognize the relevant cell types in the turkey. In the footpads of birds suffering from FPD, there were large fold increases in mRNA expression levels for the pro-inflammatory cytokines IL-1 beta (+635), IL-6 (+65), and CXCLi2 (+1924), and interferon-gamma (+32), whereas there was only a small increase in IL-13 mRNA (+2) and no change in IL-10 mRNA expression levels. CD4+ and CD8+ T lymphocytes were present in the footpads of more than 90% of birds housed on wet litter compared with 25% or less on dry litter. Macrophages were observed in the footpads of approximately 85% of birds housed on wet litter compared with none in birds housed on dry litter. B lymphocytes were not detected in tissue from any of the birds. The data suggest that FPD is associated with a rapidly occurring inflammatory response, rather than a Th2-mediated allergic reaction.