Histomonosis, Histomoniasis, Infectious Typhlohepatitis, Infectious Enterohepatitis
Histomoniasis, also known as Blackhead, is a destructive protozoan disease of predominately turkeys, and sometimes chickens. Infected birds often appear droopy, stop eating, and develop yellowish-brown, watery feces that appears foamy. The disease is caused by Histomonas meleagridis
, a protozoan parasite that is commonly found within the cecal worm (Heterakis gallinarum
), which is often harbored in earthworms. The nickname "blackhead" came from the dark colored (almost black) head and wattles of infected birds. The disease is often acute in nature, with affected individuals dying quickly, especially in younger chickens less than 6-weeks of age.
Once H. meleagridis
gains access to the digestive tract, it can multiple within the ceca and destroy the outer lining of the chicken's cecal, piling it up to form a cheese-like, foul smelling yellow substance that is composed of the dead cecal cells and blood. H. meleagridis
will eventually move on to other organs.
may spread directly through contact with contaminated feces or indirectly by ingestion of the infected egg of the cecal worm Heterakis gallinae
or ingestion of an earthworm containing cecal worm eggs. Chickens are somewhat resistant to blackhead, and can often become carriers. Carrier chickens will regularly shed cecal worm eggs in their feces, where they can remain in the soil. H. meleagridis
can survive for up to 3 years in the soil.