Histomonas meleagridis

Histomonas meleagridis is a type of protozoan parasite known to cause Histomoniasis (blackhead) in poultry. H. meleagridis is transmitted to poultry through ingestion of the nematode Heterakis gallinarum or an infected earthworm. It is more of a problem in turkeys, but infections in chicken flocks have occurred more frequently over the years.