Simple SummaryHistomonosis has become a serious disease not only for turkeys but for the entire poultry sector. Despite a focus on research on histomonosis over recent years, possible disease-favouring conditions are still poorly understood. For this reason, an interview-based case series study was initiated on 31 affected turkey farms in Germany. Despite a generally good risk awareness among participating farmers for disease-favouring conditions, an insufficient attitude towards certain biosecurity aspects was detected. Furthermore, hypotheses concerning various possibilities of pathogen introduction via animate or inanimate vectors could be generated, which need to be tested in follow-up studies. Overall, this study demonstrates that improvements in biosecurity, flock, and health management are necessary to ensure animal welfare in the future.AbstractSince the ban of effective feed additives and therapeutics, histomonosis has become an important disease and, subsequently, a welfare issue for turkey production. We conducted an interview-based case series study to generate hypotheses about possible disease-favouring conditions in 31H. meleagridis-infected flocks. The determined parameters were related to the general farm (flock management, biosecurity measures, etc.) as well as the histomonosis-specific disease management. Some inadequate biosecurity measures were observed. An inappropriate usage of the hygiene lock and cleaning as well as the disinfection frequency of equipment, clothes, and the hygiene lock could possibly be histomonosis-favouring conditions. These factors could increase the risk for the introduction ofH. meleagridisand the risk of a pathogen spread on an affected farm. Insects, wild birds, litter materials, and contaminated dung could be potential vectors ofH. meleagridis. Predisposing gastrointestinal diseases were observed in 71% of the affected flocks. Additionally, stress events related to higher temperature, movement of birds, and vaccination were documented in association with clinical histomonosis. The results emphasise the need for both good disease control and health management to ensure sustainable animal health and welfare.