HISTOMONASIS MELEAGRIDIS (BLACKHEAD DISEASE)

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Causative Agent(s)

Histomonas meleagridis

Clinical Presentation and Epidemiology

Usually fatal in turkeys (less so in other poultry).

Transmission is via embryonated eggs of Heterakis gallinarum, and sometimes directly by ingestion of faeces. The protozoa migrate into caecal mucosa and cause extensive necrosis. Organism also migrate to the liver by the vascular system or via the peritoneal cavity.

Clinical Presentation and Epidemiology

Listlessness, drooping wings, unkempt feathers, sulphur-coloured droppings. Young birds usually die acutely, while older birds die after a chronic illness.

In necropsy, there is marked inflammatory changes, thickened wall, and ulcerations in the cecum. Ulcers may erode through the wall leading to peritonitis. Cecum contains yellowish/green caseous exudate (later a dry cheesy core is seen). Rounded necrotic lesions (up to 4cm) are variably present on the liver.

Diagnostic Consideration

Liver and caecal lesions are pathognomonic when seen together. Could also be identified at histopathology.

Management and Treatment

Do NOT house chickens and turkeys together and avoid moving turkeys into areas previously contaminated by chickens. No drug is currently approved for use in poultry.