Histomoniasis (Blackhead)

Various free range chickens feeding on grass at organic farm

By Barry Whitworth, DVM

A question sometimes asked by backyard poultry enthusiasts is, “Can turkeys and chickens be raised in the same area?” A simple answer is that many backyard poultry producers do; however, many poultry experts would caution poultry producers about co-mingling these two species. The reason for this is a small protozoan parasite called Histomonas meleagridis.

H. meleagridis is a flagellated ameboid protozoan. The survival of this protozoan is dependent on Heterakis gallinarum, commonly referred to as the cecal worm of poultry. The cecal worms eat the protozoans. Once inside the cecal worm, the female cecal worm incorporates the protozoan in her eggs. The contaminated cecal worm eggs are shed in the bird’s droppings. At this time, H. meleagridis can be transmitted to domestic birds by ingestion of the contaminated cecal worm eggs or intermediated host (earthworms) that has ingested the contaminated eggs. Also, the protozoan can be transmitted directly from one bird to another bird. Unless protected in the cecal worm eggs or earthworms, H. meleagridis only survives a short period of time in the environment.

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