Histomoniasis is a commercially significant

disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

poultry Poultry () are domesticated birds kept by humans for their eggs, their meat or their feathers. These birds are most typically members of the superorder Galloanserae (fowl), especially the order Galliformes (which includes chickens, qu ...

, particularly of

chickens The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adult m ...

and turkeys, due to parasitic

infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable di ...

of a

protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

n, '' Histomonas meleagridis''. The

protozoan Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

is transmitted to the bird by the

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant- parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a bro ...

parasite ''

Heterakis gallinarum ''Heterakis gallinarum'' is a nematode parasite that lives in the cecum of some galliform birds, particularly in ground feeders such as domestic chickens and turkeys. It causes infection that is mildly pathogenic. However, it often carries a p ...

''. ''H. meleagridis'' resides within the eggs of ''H. gallinarum'', so birds

ingest Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in a substance through the mouth into the gastrointestinal tract, such as through eating or drinking. In single-celled organisms ingesti ...

the parasites along with contaminated soil or food.

Earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...

s can also act as a paratenic host. ''Histomonas meleagridis'' specifically infects the cecum and

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it i ...

Symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showi ...

of the

include

lethargy Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...

, reduced appetite, poor growth, increased thirst, sulphur-yellow

diarrhoea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

and dry, ruffled feathers. The head may become cyanotic (bluish in colour), hence the common name of the disease, blackhead disease; thus the name 'blackhead' is in all possibility a

misnomer A misnomer is a name that is incorrectly or unsuitably applied. Misnomers often arise because something was named long before its correct nature was known, or because an earlier form of something has been replaced by a later form to which the name ...

for discoloration. The disease carries a high

mortality rate Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of d ...

, and is particularly highly fatal in

, and less in other birds. Currently, no

prescription drug A prescription drug (also prescription medication or prescription medicine) is a pharmaceutical drug that legally requires a medical prescription to be dispensed. In contrast, over-the-counter drugs can be obtained without a prescription. The r ...

is approved to treat this disease.

Poultry Poultry () are domesticated birds kept by humans for their eggs, their meat or their feathers. These birds are most typically members of the superorder Galloanserae (fowl), especially the order Galliformes (which includes chickens, qu ...

(especially free-ranging) and wild birds commonly harbor a number of parasitic worms 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 Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a rela ...

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 Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology * Acute (medicine), a disease that it is of short duration and of recent onset. ** Acute toxicity, the adverse ef ...

disease and die within a few days after signs appear. Older birds may be sick for some time and become

emaciated Emaciation is defined as the state of extreme thinness from absence of body fat and muscle wasting usually resulting from malnutrition. Characteristics In humans, the physical appearance of emaciation includes thinned limbs, pronounced and protru ...

before death. The symptoms are highly fatal to turkeys, but effect less damage in chickens. However, outbreaks in chickens may result in high morbidity, moderate mortality, and extensive

culling In biology, culling is the process of segregating organisms from a group according to desired or undesired characteristics. In animal breeding, it is the process of removing or segregating animals from a breeding stock based on a specific tr ...

, leading to overall poor flock performance. Concurrence of ''

Salmonella ''Salmonella'' is a genus of rod-shaped (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two species of ''Salmonella'' are '' Salmonella enterica'' and '' Salmonella bongori''. ''S. enterica'' is the type species and is ...

typhmurium'' and '' E. coli'' was found to cause high mortality in

broiler A broiler is any chicken (''Gallus gallus domesticus'') that is bred and raised specifically for meat production. Most commercial broilers reach slaughter weight between four and six weeks of age, although slower growing breeds reach slaugh ...

chickens.

Cause

A protozoan '' H. meleagridis'' is responsible for histomoniasis of gallinaceous birds ranging from chickens, turkeys,

ducks Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form ...

, geese, grouse,

guineafowl Guineafowl (; sometimes called "pet speckled hens" or "original fowl") are birds of the family Numididae in the order Galliformes. They are endemic to Africa and rank among the oldest of the gallinaceous birds. Phylogenetically, they branched ...

, partridges, pheasants, and quails. The protozoan

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson h ...

is transmitted through the eggs of a

, ''

''. 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

the eggs of the nematode in soil, or sometimes through

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...

s which had ingested the egg-contaminated soil. Outbreak can occur rapidly from the heavily infected bird in a flock readily through normal contact between uninfected and infected birds and their droppings in the total absence of cecal

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete wor ...

s. For this reason, infection can spread very quickly. Once inside the

digestive system The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...

of the host, the

n is moved to the cecum along with the eggs of ''H. gallinarum''.

Transmission and pathology

The disease causing agent, ''Histomonas meliagridis'', is transmitted in the eggs of the worm ''Heterakis gallinarum''. 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. Bird to bird transmission can also occur from cloacal drinking 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.

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 A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...

and

submucosa The submucosa (or tela submucosa) is a thin layer of tissue in various organs of the gastrointestinal, respiratory, and genitourinary tracts. It is the layer of dense irregular connective tissue that supports the mucosa (mucous membrane) and j ...

where they cause extensive and severe

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated diges ...

of the tissue. Necrosis is initiated by

inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

and gradual ulceration, causing thickening of the cecal wall. The

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classif ...

s are sometimes exacerbated by other pathogens such as ''

Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...

'' and

coccidia Coccidia (Coccidiasina) are a subclass of microscopic, spore-forming, single-celled obligate intracellular parasites belonging to the apicomplexan class Conoidasida. As obligate intracellular parasites, they must live and reproduce within an a ...

. Histomonads then gain entry into small

veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated ...

of the blood stream from the cecal lesions and migrate to the

, causing focal necrosis. Turkeys are noted to be most susceptible to the symptoms in terms of mortality, sometimes approaching 100% of a flock.

Diagnosis Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine "cause and effect". In systems engin ...

can be easily performed by necropsy of the fresh or preserved carcass. Unusual lesions have been observed in other organs of turkey such as the bursa of Fabricius,

lungs The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either si ...

, and kidneys.

Prevention and treatment

Currently, no therapeutic

drugs A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via inhalati ...

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.

Deworming Deworming (sometimes known as worming, drenching or dehelmintization) is the giving of an anthelmintic drug (a wormer, dewormer, or drench) to a human or animals to rid them of helminths parasites, such as roundworm, flukes and tapeworm. Pur ...

of birds with anthelmintics can reduce exposure to the cecal nematodes that carry the protozoan. Good management of the farm, including immediate

quarantine A quarantine is a restriction on the movement of people, animals and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have been ...

of infected birds and sanitation, is the main useful strategy for controlling the spread of the parasitic contamination. The only drug used for the control ( prophylaxis) in the United States is ( nitarsone) at 0.01875% of feed until 5 days before marketing. Natustat and nitarsone were shown to be effective therapeutic drugs. As of the end of 2015, the FDA has proscribed arsenical drugs in poultry in the US.

Nifurtimox Nifurtimox, sold under the brand name Lampit, is a medication used to treat Chagas disease and sleeping sickness. For sleeping sickness it is used together with eflornithine in nifurtimox-eflornithine combination treatment. In Chagas disease ...

, a compound with known

antiprotozoal Antiprotozoal agents ( ATC code: ATC P01) is a class of pharmaceuticals used in treatment of protozoan infection. A paraphyletic group, protozoans have little in common with each other. For example, ''Entamoeba histolytica'', a unikont eukar ...

activity, was demonstrated to be significantly effective at 300–400 ppm, and well tolerated by turkeys.

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. It has been found in turkeys, chickens, guinea fowl, and other game birds. Bobwhite quail can also be infected.

References

External links

* * {{Authority control Protozoal diseases Poultry diseases Veterinary protozoology