Modulating the avian cecal microbiome: probiotics in the prevention of Histomonas meleagridis in poultry

Histomoniasis is a serious infectious enteric disease that mainly affects gallinaceous poultry in all parts of the world. The protozoan parasite, Histomonas meleagridis is the causative agent. Once regulated by synthetic chemical additives, the disease has resurged globally since the banning of effective yet probably toxic pharmacological prophylactic agents. The pathogenesis of Histomonas meleagridis has a complicated interaction with the avian cecal microbiome, which is discussed in this review. Infection leads to active induction of deep dysbiosis by the parasite that drastically decreases the number of beneficial bacteria and increases growth of opportunistic pathogens. The scientifically feasible option of mitigating diseases by modulating the cecal ecosystem with targeted probiotic administration has come up. This review explains the biological processes of the parasite, the homeostatic role of the microbiome, and the high standards of selection of poultry probiotics. Crucially, while most current evidence remains indirect due to a lack of targeted in vivo models, this review uniquely explains how probiotics utilize competitive exclusion and immunomodulatory mechanisms to reverse parasitic colonization. By comparing these microbial interventions to existing avian prophylaxis, this manuscript highlights the practical significance of precision microbiome modulation in commercial flocks and sets the stage for future targeted experimental research.