# Histomoniasis

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{{Infobox medical condition (new)
| name            = Histomoniasis
| synonyms        = Histomonosis, blackhead disease
| image           = Histomoniasis.jpg
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| caption         = Large, pale areas in the liver of a bird infected with ''Histomonas meleagridis''
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| field           = [Veterinary medicine](/source/Veterinary_medicine)
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'''Histomoniasis''' is a commercially significant [disease](/source/disease) of [poultry](/source/poultry), particularly of [chickens](/source/chickens) and [turkeys](/source/turkeys), due to [parasitic](/source/parasitic) [infection](/source/infection) of a [protozoa](/source/protozoa)n, ''[Histomonas meleagridis](/source/Histomonas_meleagridis)''. The [protozoan](/source/protozoan) is transmitted to the bird by the [nematode](/source/nematode) parasite ''[Heterakis gallinarum](/source/Heterakis_gallinarum)''.<ref>{{cite journal|vauthors=Lund EE, Chute AM, Wilkins GC |s2cid=45359310 |title=The wild turkey as a host for ''Heterakis gallinarum'' and ''Histomonas meleagridis'' |journal=Journal of Wildlife Diseases |volume=11 |issue=3 |pages=376–381 |year=1975 |pmid=1171270 |doi=10.7589/0090-3558-11.3.376}}{{open access}}</ref><ref>{{cite journal|vauthors=Brener B, Tortelly R, Menezes RC, Muniz-Pereira LC, Pinto RM |title=Prevalence and pathology of the nematode ''Heterakis gallinarum'', the trematode ''Paratanaisia bragai'', and the protozoan ''Histomonas meleagridis'' in the turkey, ''Meleagris gallopavo'' |journal=Memórias do Instituto Oswaldo Cruz |volume=101 |issue=6 |pages=677–681 |year=2006 |pmid=17072483 |doi=10.1590/s0074-02762006000600017|doi-access=free }}{{open access}}</ref> ''H. meleagridis'' resides within the eggs of ''H. gallinarum'', so birds [ingest](/source/ingest) the parasites along with contaminated soil or food.<ref name="MCDG"/> [Earthworm](/source/Earthworm)s can also act as a [paratenic](/source/paratenic) host.

''Histomonas meleagridis'' specifically infects the [cecum](/source/cecum) and [liver](/source/liver). [Symptoms](/source/Symptoms) of the [infection](/source/infection) include [lethargy](/source/lethargy), reduced [appetite](/source/appetite), poor growth, increased thirst, sulphur-yellow [diarrhoea](/source/diarrhoea) and dry, ruffled [feathers](/source/feathers). The head may become [cyanotic](/source/cyanosis) (bluish in colour), hence the common name of the disease, blackhead disease; thus the name 'blackhead' is in all possibility a [misnomer](/source/misnomer) for discoloration.<ref>Davidson DR, Doster GL. [http://www.nwtf.org/conservation/bulletins/bulletin_25.pdf Blackhead Disease does not Really Cause Black Heads.] {{webarchive|url=https://web.archive.org/web/20110516075123/http://www.nwtf.org/conservation/bulletins/bulletin_25.pdf |date=2011-05-16 }} NWTF Wilflife Bulletin No. 25, pp. 25(1-4).</ref> The disease carries a high [mortality rate](/source/mortality_rate), and is particularly highly fatal in [poultry](/source/poultry), and less in other birds. Currently, no [prescription drug](/source/prescription_drug) is approved to treat this disease.<ref name="MCDG">{{cite journal |journal=Poultry Science |pmid=9706082 |year=1998 |last1=McDougald |first1=LR |title=Intestinal protozoa important to poultry |volume=77 |issue=8 |pages=1156–8 |doi=10.1093/ps/77.8.1156|doi-access=free }}{{open access}}</ref>

[Poultry](/source/Poultry) (especially [free-ranging](/source/free_range)) and wild birds commonly harbor a number of [parasitic worms](/source/Nematode) with only mild health problems from them. Turkeys are much more susceptible to getting blackhead than are chickens. Thus, chickens can be infected carriers for a long time because they are not removed or medicated by their owners, and they do not die or stop eating/defecating. ''H. gallinarum'' eggs can remain infective in soil for four years, a high risk of transmitting blackhead to turkeys remains if they graze areas with chicken [feces](/source/feces)<ref>{{cite web|url=http://edis.ifas.ufl.edu/VM015|title=Intestinal Parasites in Backyard Chicken Flocks|first=Gary D. Butcher and Richard D.|last=Miles|date=19 June 2015}}</ref> in this time frame.

==Symptoms==
Symptoms appear within 7–12 days after infection and include depression, reduced appetite, poor growth, increased thirst, sulphur-yellow diarrhoea, listlessness, drooping wings, and unkempt feathers. Young birds have a more [acute](/source/Acute_(medicine)) disease and die within a few days after signs appear. Older birds may be sick for some time and become [emaciated](/source/emaciated) before death. The symptoms are highly fatal to turkeys, but effect less damage in chickens. However, outbreaks in chickens may result in high [morbidity](/source/morbidity), moderate mortality, and extensive [culling](/source/culling), leading to overall poor flock performance.<ref name="MCDG"/> Concurrence of ''[Salmonella](/source/Salmonella) typhmurium'' and ''[E. coli](/source/Escherichia_coli)'' was found to cause high mortality in [broiler](/source/broiler) chickens.<ref>{{cite journal |journal= Avian Pathology |doi=10.1080/03079450020016000 |pmid=19184862 |title= Concurrent occurrence of salmonellosis, colibaccillosis and histomoniasis in a broiler flock fed with antibiotic-free commercial feed |year= 2000 |last1= Ganapathy |first1= K. |last2= Salamat |first2= M. H. |last3= Lee |first3= C. C. |last4= Johara |first4= M. Y. |s2cid=25256520 |volume= 29 |issue= 6 |pages= 639–42|doi-access= free }}</ref>

== Cause ==
A protozoan ''[H. meleagridis](/source/Histomonas_meleagridis)'' is responsible for histomoniasis of [gallinaceous birds](/source/galliformes) ranging from chickens, turkeys, [ducks](/source/ducks), [geese](/source/geese), [grouse](/source/grouse), [guineafowl](/source/guineafowl), [partridges](/source/partridges), [pheasants](/source/pheasants), and [quails](/source/quails). The protozoan [parasite](/source/parasite) is transmitted through the eggs of a [nematode](/source/nematode), ''[Heterakis gallinarum](/source/Heterakis_gallinarum)''. The eggs are highly resistant to environmental conditions, and ''H. meleagridis'' is, in turn, highly viable inside the eggs, even for years. Birds are infected once they [ingest](/source/ingest) the eggs of the nematode in soil, or sometimes through [earthworm](/source/earthworm)s which had [ingested](/source/ingested) the egg-contaminated soil. [Outbreak](/source/Outbreak) can occur rapidly from the heavily infected bird in a [flock](/source/flocking_(behavior)) readily through normal contact between uninfected and infected birds and their [droppings](/source/droppings) in the total absence of [cecal](/source/cecum) [worm](/source/worm)s.<ref>{{cite journal |title=Direct lateral transmission of ''Histomonas meleagridis'' in turkeys |journal=Avian Diseases |doi=10.1637/0005-2086(2003)047[0489:DLTOHM]2.0.CO;2 |pmid=12887212 |year=2003 |volume=47 |pages=489–92 |last1=Hu |first1=Jinghui |last2=McDougald |first2=L. R. |issue=2}}</ref> For this reason, infection can spread very quickly. Once inside the [digestive system](/source/digestive_system) of the host, the [protozoa](/source/protozoa)n is moved to the [cecum](/source/cecum) along with the eggs of ''H. gallinarum''.<ref name="MCD">{{cite journal |journal=Avian Diseases |pmid=16404985 |year=2005 |last1=McDougald |first1=LR |s2cid=43031620 |title=Blackhead disease (histomoniasis) in poultry: A critical review |volume=49 |issue=4 |pages=462–76 |doi=10.1637/7420-081005R.1}}</ref>

===Transmission and pathology===
The disease causing agent, ''Histomonas meliagridis'', is transmitted in the eggs of the worm ''Heterakis gallinarum''.<ref name="MCD"/> Once in the environment, the eggs are carried by earthworms. When the worms are eaten and the eggs hatch in the ceca, the pathogen is released.<ref name="poultry207"/> Bird to bird transmission can also occur from cloacal drinking <ref>McDougald, Larry R, PhD. The Poultry Site: Histomonosis. Retrieved from http://www.thepoultrysite.com/articles/1285/control-of-blackhead-disease/</ref>

Visible signs of this disease are cyanosis of the head (hence, “blackhead”) and sulfur-yellow diarrhea. The pathogen causes lesions on the ceca and the liver. The ceca experience ulcerations, enlargement, and caseous masses start to form inside of them. The liver develops round, haemorrhagic, 1-2 centimeter oci that have caseous cores.<ref name="poultry207"/>

== Diagnosis ==
Histomoniasis is characterized by blackhead in birds. ''H. meleagridis'' is released in the cecum where the eggs of the nematode undergo larval development. The parasite migrates to the [mucosa](/source/mucosa) and [submucosa](/source/submucosa) where they cause extensive and severe [necrosis](/source/necrosis) of the tissue. Necrosis is initiated by [inflammation](/source/inflammation) and gradual [ulceration](/source/Peptic_ulcer), causing thickening of the cecal wall. The [lesion](/source/lesion)s are sometimes exacerbated by other [pathogens](/source/pathogens) such as ''[Escherichia coli](/source/Escherichia_coli)'' and [coccidia](/source/coccidia). Histomonads then gain entry into small [veins](/source/veins) of the [blood stream](/source/blood_stream) from the cecal lesions and migrate to the [liver](/source/liver), causing focal necrosis. Turkeys are noted to be most susceptible to the symptoms in terms of [mortality](/source/Mortality_rate), sometimes approaching 100% of a flock.<ref name="MCD"/> [Diagnosis](/source/Diagnosis) can be easily performed by [necropsy](/source/necropsy) of the fresh or preserved carcass. Unusual lesions have been observed in other organs of turkey such as the [bursa of Fabricius](/source/bursa_of_Fabricius), [lungs](/source/lungs), and [kidneys](/source/kidneys).<ref>{{cite journal |doi=10.1637/8363-051508-Reg.1 |title=Systemic Histomoniasis Associated with High Mortality and Unusual Lesions in the Bursa of Fabricius, Kidneys, and Lungs in Commercial Turkeys |date=2009 |last1=Sentíes-Cué |first1=Gabriel |last2=Chin |first2=R. P. |last3=Shivaprasad |first3=H. L. |journal=Avian Diseases |volume=53 |issue=2 |pages=231–238 |pmid=19630229 |s2cid=41063366 }}</ref>

== Prevention and treatment ==
Currently, no therapeutic [drugs](/source/drugs) are prescribed for the disease. Therefore, prevention is the sole mode of treatment. This disease can be prevented only by quarantining sick birds and preventing migration of birds around the house, causing them to spread the disease.<ref>McDougald, Larry R, PhD. The Poultry Site: Histomonosis. Retrieved from http://www.thepoultrysite.com/publications/6/diseases-of-poultry/207/histomonosis/</ref> [Deworming](/source/Deworming) of birds with [anthelmintics](/source/anthelmintics) can reduce exposure to the cecal nematodes that carry the protozoan. Good management of the farm, including immediate [quarantine](/source/quarantine) of infected birds and sanitation, is the main useful strategy for controlling the spread of the parasitic contamination.<ref>{{cite journal |journal=Epidemiology and Infection |pmid=19664306 |doi=10.1017/S0950268809990562 |title=Flock management and histomoniasis in free-range turkeys in France: Description and search for potential risk factors |year=2009 |last1=Callait-Cardinal |first1=M. P. |last2=Gilot-Fromont |first2=E. |last3=Chossat |first3=L. |last4=Gonthier |first4=A. |last5=Chauve |first5=C. |last6=Zenner |first6=L. |volume=138 |issue=3 |pages=353–63|doi-access=free }}</ref> The only drug used for the control ([prophylaxis](/source/prophylaxis)) in the United States is ([nitarsone](/source/nitarsone)) at 0.01875% of feed until 5 days before marketing. Natustat and nitarsone were shown to be effective therapeutic drugs.<ref>{{cite journal|title=Evaluation of dietary Natustat for control of ''Histomonas meleagridis'' in male turkeys on infected litter |journal=Avian Diseases |doi=10.1637/7344-022105R2.1 |pmid=16252499|year=2005|last1=Duffy|first1=C. F.|last2=Sims|first2=M. D.|last3=Power|first3=R. F.|s2cid=25315125 |volume=49|issue=3|pages=423–5}}</ref> As of the end of 2015, the FDA has proscribed arsenical drugs in poultry in the US.<ref>{{cite news | author = U.S. Food and Drug Administration | url =https://www.fda.gov/AnimalVeterinary/NewsEvents/CVMUpdates/ucm440668.htm | archive-url =https://web.archive.org/web/20150404001249/http://www.fda.gov/AnimalVeterinary/NewsEvents/CVMUpdates/ucm440668.htm | url-status =dead | archive-date =April 4, 2015 | title =FDA Announces Pending Withdrawal of Approval of Nitarsone | date = April 1, 2015}}</ref>  [Nifurtimox](/source/Nifurtimox), a compound with known [antiprotozoal](/source/antiprotozoal_agent) activity, was demonstrated to be significantly effective at 300–400 [ppm](/source/Parts_per_million), and well tolerated by turkeys.<ref>{{cite journal |journal=Avian Diseases |doi= 10.1637/9011-081209-Reg.1 |title=Evaluation of Nifurtimox for Potential Use in Control of Histomoniasis in Turkeys |year=2010 |last1=Hauck |first1=Rüdiger |last2=Fuller |first2=A. L. |last3=Greif |first3=Gisela |last4=McDougald |first4=L. R. |s2cid= 24953201 |volume=54 |pages=28–32 |pmid=20408395 |issue=1}}</ref>

==History==
The disease was initially discovered in Rhode Island in the year 1893. Soon after, it was shown to have devastating effects on the turkey industry, especially in New England, dropping production from 11 million birds in 1890 to 6.6 million in 1900. However, improvements in turkey management have curbed the effects of this disease. It has since spread across the globe.<ref name="MCD"/> It has been found in turkeys, chickens, guinea fowl, and other game birds.<ref name="poultry207">{{cite web|last1=Dinev|first1=Ivan|title=Histomonosis - Diseases of Poultry|url=http://www.thepoultrysite.com/publications/6/diseases-of-poultry/207/histomonosis/|website=The Poultry Site|language=en}}</ref> Bobwhite quail can also be infected.<ref>{{cite journal|last1=McDougald|first1=LR|last2=Abraham|first2=M|last3=Beckstead|first3=RB|s2cid=31323766|title=An outbreak of blackhead disease (''Histomonas meleagridis'') in farm-reared bobwhite quail (''Colinus virginianus'')|journal=Avian Diseases|date=December 2012|volume=56|issue=4|pages=754–6|doi=10.1637/10140-032212-Case.1|pmid=23397851|jstor=23322268}}</ref>

== References ==
{{Reflist}}

== External links ==

* {{Wiktionary-inline}}
* {{Commons-inline}}

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Category:Protozoal diseases
Category:Poultry diseases
Category:Veterinary protozoology

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Adapted from the Wikipedia article [Histomoniasis](https://en.wikipedia.org/wiki/Histomoniasis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Histomoniasis?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.