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Related to histomoniasis: Blackhead disease, Histomonas meleagridis


The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


A protozoa infection by Histomonas meleagridis, which involves the caeca and later the liver, of turkeys (in which it is often fatal), chickens and other galliform birds.

The causative agent, Histomonas meleagridis, is typically transmitted in embryonated eggs of the cecal nematode Heterakis gallinarum , or by direct contact with infected birds.

Clinical findings
Listlessness, drooping wings, unkempt feathers and yellow droppings. Young birds have more acute disease and die within a few days; older birds tend to live longer.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


A disease chiefly affecting turkeys, caused by Histomonas meleagridis and characterized by ulcerative and necrotic lesions of the liver and cecum, acute onset, and a high mortality rate. It is transmitted inside the eggs of the nematode Heterakis gallinae, which is primarily responsible for maintaining and spreading the infection.
Synonym(s): blackhead (2) .
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
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The economic significance of histomoniasis is difficult to ascertain, but annual losses from mortality in turkeys has been estimated to exceed two million dollars in the United States (McDougald, 1997).
The FDA withdrew marketing approvals for roxarsone and for two other arsenic-based feed additives in 2013, and they withdrew approval for nitarsone, which is used to prevent histomoniasis in turkeys, in December of 2015 (FDA 2014b, 2015; Abraham et al.
Blackhead, or histomoniasis, is caused by a microscopic parasite which attacks the birds' livers.
Histopathologic evaluation of the liver, ceca, kidney, spleen, and small intestine revealed systemic histomoniasis (SH) associated with intralesional and intravascular accumulations of histomonad organisms consistent with H meleagridis.
The Maryland ban exempts Histostat[R] (nitarsone), another Alpharma arsenical for use in poultry, which is the only FDA-approved treatment for histomoniasis, a potentially lethal illness.
Gross and microscopic lesions were observed on days 7, 14, 21, 28, and 35 post infection to evaluate any clinical histomoniasis in ducks and to appraise the histomonad's carriage.