Histomonas meleagridis
Encyclopedia
Histomonas meleagridis is species of parasitic protozoa
n that infects a wide range of birds including chicken
s, turkey
s, peafowl
, quail
and pheasant
s, causing blackhead disease
, infectious enterohepatitis, or histomoniasis
. H. meleagridis can infect many birds but it is most deadly in turkeys. It inhabits the lumen
of cecum
and parenchyma
of liver
where it causes extensive necrosis
. It is transmitted by another cecal
parasite, the nematode
Heterakis gallinarum
.
, pleomorphic protozoan and can exist in dimorphic
forms, amoeboid
and flagellated
. Within the tissue it is present as an amoeboid
protozoan, while in the lumen
or free in the contents of cecum
it lives as an elongated flagellated
form. The amoeboid
form is typically 8-15 μm
in diameter, whereas the flagellated
form can reach up to 30 μm
in diameter.
, a cecal nematode
, which in turn can be transmitted by earthworms that ingested the nematode
eggs, they gain entry into the nematode
eggs. The eggs with the trophozoites are passed out into the environment through the feces
. In this way the trophozoites can remain viable for 1–2 years in the external environment. Within turkey
flocks H. meleagridis is also known to be directly transmitted from bird to bird. Histomonads, either released from the heterakid nematode
larva
e in the ceca
or after direct infection via the cloaca
, and replicate rapidly in the cecal
tissues. They migrate to the submucosa
and muscularis mucosae and cause severe necrosis
. The parasites then move to the liver
through the vascular system. There they cause typical crater-like necrotic
lesions. Mortality
in turkey
flocks can be very high (80-100%).
of histomoniasis
of gallinaceous birds
. It induces extensive and severe necrosis
of the tissues of the mucosa and submucosa
of cecum
and parenchyma
of the liver
. The lesions are sometimes exacerbated by other pathogens such as Escherichia coli
and coccidia
. The 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. The symptoms are highly fatal
to turkeys, but affect less damage in chickens. However, outbreak
s in chickens may result in high morbidity, moderate mortality, and extensive culling
, leading to overall poor flock
performance. Concurrence of Salmonella
typhmurium and E. coli
was found to cause high mortality in broiler
chickens. Young birds particularly of 3–12 weeks olds are most susceptible. Generally the symptoms are profound in turkeys while chickens are usually asymptomatic
.
can be easily performed by autopsy
of the fresh or preserved carcass
, particularly on the liver
. There are no prescription drugs available for this parasite as of today. Therefore, good management of the farm
and sanitation
are the only effective strategies to control the spread of infection.
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...
n that infects a wide range of birds including chicken
Chicken
The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...
s, turkey
Turkey (bird)
A turkey is a large bird in the genus Meleagris. One species, Meleagris gallopavo, commonly known as the Wild Turkey, is native to the forests of North America. The domestic turkey is a descendant of this species...
s, peafowl
Peafowl
Peafowl are two Asiatic species of flying birds in the genus Pavo of the pheasant family, Phasianidae, best known for the male's extravagant eye-spotted tail, which it displays as part of courtship. The male is called a peacock, the female a peahen, and the offspring peachicks. The adult female...
, quail
Quail
Quail is a collective name for several genera of mid-sized birds generally considered in the order Galliformes. Old World quail are found in the family Phasianidae, while New World quail are found in the family Odontophoridae...
and pheasant
Pheasant
Pheasants refer to some members of the Phasianinae subfamily of Phasianidae in the order Galliformes.Pheasants are characterised by strong sexual dimorphism, males being highly ornate with bright colours and adornments such as wattles and long tails. Males are usually larger than females and have...
s, causing blackhead disease
Blackhead disease
Blackhead disease is a commercially important avian disease that affects chickens, turkeys and other poultry birds. The disease carries a high mortality rate and primarily affects the liver and cecum. It is a form of histomoniasis which is transmitted by the protozoan parasite Histomonas meleagridis...
, infectious enterohepatitis, or histomoniasis
Histomoniasis
Histomoniasis is a disease of birds, particularly of chickens and turkeys, due to parasitic infection of a protozoan, Histomonas meleagridis. It is a form of blackhead disease in poultry. The parasite specifically infects the cecum and liver...
. H. meleagridis can infect many birds but it is most deadly in turkeys. It inhabits the lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
of cecum
Cecum
The cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...
and parenchyma
Parenchyma
Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...
of liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
where it causes extensive necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
. It is transmitted by another cecal
Cecum
The cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...
parasite, the nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
Heterakis gallinarum
Heterakis gallinarum
Heterakis gallinarum is a nematode parasite that lives in the cecum of domestic fowl, particularly in ground feeders such as domestic chickens and turkeys. It causes infection that is mildly pathogenic. However it often carries a protozoan parasite Histomonas meleagridis which causes of...
.
Description
H. meleagridis is a microscopicMicroscopic
The microscopic scale is the scale of size or length used to describe objects smaller than those that can easily be seen by the naked eye and which require a lens or microscope to see them clearly.-History:...
, pleomorphic protozoan and can exist in dimorphic
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
forms, amoeboid
Amoeboid
Amoeboids are single-celled life-forms characterized by an irregular shape."Amoeboid" and "amœba" are often used interchangeably even by biologists, and especially refer to a creature moving by using pseudopodia. Most references to "amoebas" or "amoebae" are to amoeboids in general rather than to...
and flagellated
Flagellation
Flagellation or flogging is the act of methodically beating or whipping the human body. Specialised implements for it include rods, switches, the cat o' nine tails and the sjambok...
. Within the tissue it is present as an amoeboid
Amoeboid
Amoeboids are single-celled life-forms characterized by an irregular shape."Amoeboid" and "amœba" are often used interchangeably even by biologists, and especially refer to a creature moving by using pseudopodia. Most references to "amoebas" or "amoebae" are to amoeboids in general rather than to...
protozoan, while in the lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
or free in the contents of cecum
Cecum
The cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...
it lives as an elongated flagellated
Flagellation
Flagellation or flogging is the act of methodically beating or whipping the human body. Specialised implements for it include rods, switches, the cat o' nine tails and the sjambok...
form. The amoeboid
Amoeboid
Amoeboids are single-celled life-forms characterized by an irregular shape."Amoeboid" and "amœba" are often used interchangeably even by biologists, and especially refer to a creature moving by using pseudopodia. Most references to "amoebas" or "amoebae" are to amoeboids in general rather than to...
form is typically 8-15 μm
Micrometer
A micrometer , sometimes known as a micrometer screw gauge, is a device incorporating a calibrated screw used widely for precise measurement of small distances in mechanical engineering and machining as well as most mechanical trades, along with other metrological instruments such as dial, vernier,...
in diameter, whereas the flagellated
Flagellation
Flagellation or flogging is the act of methodically beating or whipping the human body. Specialised implements for it include rods, switches, the cat o' nine tails and the sjambok...
form can reach up to 30 μm
Micrometer
A micrometer , sometimes known as a micrometer screw gauge, is a device incorporating a calibrated screw used widely for precise measurement of small distances in mechanical engineering and machining as well as most mechanical trades, along with other metrological instruments such as dial, vernier,...
in diameter.
Life cycle
H. meleagridis reproduce by binary fission. The free trophozoites are very delicate and can survive only for a few hours in the external environment. However, when they are transmitted between flocks in the eggs of H. gallinarumHeterakis gallinarum
Heterakis gallinarum is a nematode parasite that lives in the cecum of domestic fowl, particularly in ground feeders such as domestic chickens and turkeys. It causes infection that is mildly pathogenic. However it often carries a protozoan parasite Histomonas meleagridis which causes of...
, a cecal nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
, which in turn can be transmitted by earthworms that ingested the nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
eggs, they gain entry into the nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
eggs. The eggs with the trophozoites are passed out into the environment through the feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
. In this way the trophozoites can remain viable for 1–2 years in the external environment. Within turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
flocks H. meleagridis is also known to be directly transmitted from bird to bird. Histomonads, either released from the heterakid nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e in the ceca
Cecum
The cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...
or after direct infection via the cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
, and replicate rapidly in the cecal
Cecum
The cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...
tissues. They migrate to the submucosa
Submucosa
In the gastrointestinal tract, the submucosa is the layer of dense irregular connective tissue or loose connective tissue that supports the mucosa, as well as joins the mucosa to the bulk of underlying smooth muscle .-Contents:Blood vessels, lymphatic vessels, and nerves will run through...
and muscularis mucosae and cause severe necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
. The parasites then move to the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
through the vascular system. There they cause typical crater-like necrotic
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
lesions. Mortality
Mortality rate
Mortality rate is a measure of the number of deaths in a population, scaled to the size of that population, per unit time...
in turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
flocks can be very high (80-100%).
Pathogenicity
H. meleagridis is the causal organismOrganism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
of histomoniasis
Histomoniasis
Histomoniasis is a disease of birds, particularly of chickens and turkeys, due to parasitic infection of a protozoan, Histomonas meleagridis. It is a form of blackhead disease in poultry. The parasite specifically infects the cecum and liver...
of gallinaceous birds
Galliformes
Galliformes are an order of heavy-bodied ground-feeding domestic or game bird, containing turkey, grouse, chicken, New and Old World Quail, ptarmigan, partridge, pheasant, and the Cracidae. Common names are gamefowl or gamebirds, landfowl, gallinaceous birds or galliforms...
. It induces extensive and severe necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
of the tissues of the mucosa and submucosa
Submucosa
In the gastrointestinal tract, the submucosa is the layer of dense irregular connective tissue or loose connective tissue that supports the mucosa, as well as joins the mucosa to the bulk of underlying smooth muscle .-Contents:Blood vessels, lymphatic vessels, and nerves will run through...
of cecum
Cecum
The cecum or caecum is a pouch, connecting the ileum with the ascending colon of the large intestine. It is separated from the ileum by the ileocecal valve or Bauhin's valve, and is considered to be the beginning of the large intestine. It is also separated from the colon by the cecocolic...
and parenchyma
Parenchyma
Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...
of the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
. The lesions are sometimes exacerbated by other pathogens such as Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
and coccidia
Coccidia
Coccidia is a subclass of microscopic, spore-forming, single-celled obligate parasites belonging to the apicomplexan class Conoidasida. Coccidian parasites infect the intestinal tracts of animals, and are the largest group of apicomplexan protozoa....
. The symptoms appear within 7–12 days after infection and include depression
Depression (mood)
Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...
, reduced appetite
Appetite
The appetite is the desire to eat food, felt as hunger. Appetite exists in all higher life-forms, and serves to regulate adequate energy intake to maintain metabolic needs. It is regulated by a close interplay between the digestive tract, adipose tissue and the brain. Decreased desire to eat is...
, poor growth, increased thirst, sulphur-yellow diarrhoea, listlessness, drooping wings, and unkempt feathers. The symptoms are highly fatal
Fatal
Fatal may refer to:* Causing death* Fatal , an album by Hussein Fatal* Fatal Recordings, a feminist record label* Fatal, a rapper who collaborated with the band Therapy? on the song "Come and Die" from the Judgment Night film soundtrack...
to turkeys, but affect less damage in chickens. However, outbreak
Outbreak
Outbreak is a term used in epidemiology to describe an occurrence of disease greater than would otherwise be expected at a particular time and place. It may affect a small and localized group or impact upon thousands of people across an entire continent. Two linked cases of a rare infectious...
s in chickens may result in high morbidity, moderate mortality, and extensive culling
Culling
Culling is the process of removing animals from a group based on specific criteria. This is done either to reinforce certain desirable characteristics or to remove certain undesirable characteristics from the group...
, leading to overall poor flock
Flock
-Computing:* Flock , a defunct web browser* Flock system call, used for computer file locking* F-Lock, a function lock key on a computer keyboard-Entertainment:* Flock , a sculpture by Michael Christian...
performance. Concurrence of Salmonella
Salmonella
Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...
typhmurium and E. coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
was found to cause high mortality in broiler
Broiler
A broiler is a type of chicken raised specifically for meat production. Modern commercial broilers, typically known as Cornish crosses or Cornish-Rocks are specially bred for large scale, efficient meat production and grow much faster than egg or traditional dual purpose breeds...
chickens. Young birds particularly of 3–12 weeks olds are most susceptible. Generally the symptoms are profound in turkeys while chickens are usually asymptomatic
Asymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
.
Diagnosis and control
DiagnosisDiagnosis
Diagnosis is the identification of the nature and cause of anything. Diagnosis is used in many different disciplines with variations in the use of logics, analytics, and experience to determine the cause and effect relationships...
can be easily performed by autopsy
Autopsy
An autopsy—also known as a post-mortem examination, necropsy , autopsia cadaverum, or obduction—is a highly specialized surgical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present...
of the fresh or preserved carcass
Carcass
Carcass may refer to:*Cadaver of a human, or carrion of an animal.*Carcass , a death metal/grindcore band*Carcass , a type of incendiary ammunition designed to be fired from a cannon, three ships of the Royal Navy...
, particularly on the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
. There are no prescription drugs available for this parasite as of today. Therefore, good management of the farm
Farm
A farm is an area of land, or, for aquaculture, lake, river or sea, including various structures, devoted primarily to the practice of producing and managing food , fibres and, increasingly, fuel. It is the basic production facility in food production. Farms may be owned and operated by a single...
and sanitation
Sanitation
Sanitation is the hygienic means of promoting health through prevention of human contact with the hazards of wastes. Hazards can be either physical, microbiological, biological or chemical agents of disease. Wastes that can cause health problems are human and animal feces, solid wastes, domestic...
are the only effective strategies to control the spread of infection.