Synonyms
Histomoniasis, infectious enterohepatitis, black head disease.
Aetiology
Histomonas meleagridis , a flagellated ameboid protozoan often disseminated by the ova or egg of Heterakis gallinarium. Histomonas does not survive for long outside the ova of the caecal worm.
Age/host affected
Susceptible species are turkeys, chickens, pheasants, guinea fowls and geese. Turkeys are most vulnerable at 3-12 weeks of age while chickens at 4-6 weeks of age.
Transmission
Transmitted by ingestion of embryonated eggs of Heterakis gallinarium carrying viable histomonads.
Disseminated by ingestion of earthworms which accidentally ingest egg of Heterakis gallinarium carrying viable histomonads.
Direct transmission by ingestion of viable histomonads in fresh droppings of infected birds.
Clinical signs
Depression
Inappetence
Poor growth
Sulphur-yellow diarrhea
Cyanosis of head leads to the term black head disease especially in turkeys.
Blood in faeces(chickens).
Progressive emaciation.
Post-mortem lesions
Caeca enlargement , ulcers, caseous cores with yellow, grey or green areas.
Liver may have irregular-round indented lesions, usually grey in colour, however they may not be present in the early stages especially chickens.
Diagnosis
This is based on clinical signs and post-mortem lesions, scrapings from fresh material.
Treatment
Nitro-imidazoles(such as dimetridazole), nitrofurans(such as furazolidone, nifursol) and arsenicals(such as nitarsone) have been used to treat this disease of poultry.
Prevention
Good sanitation
Avoid mixing species
Poultry houses should be built on concrete floors
Regular deworming to help control the intermediate hosts.