Blackhead Disease

Symptom

The crest appears black – due to the infection with the amoeboflagellate.

General Information

Histomonas meleagridis is present in many species of turkeys, chicken, or other birds. The motile parasitic stages (Fig. 1) reach a size of 10–30 μm, some appear with one flagellum others without flagellum, as spherical stage or as slightly amoeboid stage. Stages with two nuclei are apparently in the phase of division (Fig. 1, right below). Recently cyst-like stages also had been described (Fig. 2). The (rarely) reported stages with 2–4 flagella are probably not Histomonas but due to coinfections with other flagellates.

Fig. 1

Light micrographs and drawings of uniflagellated and amoeboid stages, of which one is apparently in division (right below) showing two nuclei