Blackhead disease
Encyclopedia
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
that affects 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 and other poultry birds
Poultry
Poultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...
. The disease carries a high mortality rate
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...
and primarily affects 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...
and 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 is a form 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...
which is transmitted by the protozoan parasite Histomonas meleagridis
Histomonas meleagridis
Histomonas meleagridis is species of parasitic protozoan that infects a wide range of birds including chickens, turkeys, peafowl, quail and pheasants, causing blackhead disease, infectious enterohepatitis, or histomoniasis. H. meleagridis can infect many birds but it is most deadly in turkeys...
. The protozoan is in turn transmitted by 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...
parasite 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...
. H. meleagridis resides within the eggs of H. gallinarum, so birds ingest the parasites along with contaminated soil or food. Earthworm
Earthworm
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...
s can also act as a paratenic
Paratenic
In parasitology, the term paratenic describes a host which is not needed for the development of the parasite, but nonetheless serves to maintain the life cycle of the parasite. Alaria americana may serve as an example: the so-called mesocercarial stages of this parasite reside in tadpoles, which...
host. A characteristic symptom
Symptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
of the infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
is the development of cyanotic
Cyanotic
Cyanotic is a Chicago-based industrial rock collective fronted by Sean Payne that formed in 2002 and released its first full-length album in 2005. Cyanotic is known for its genre-blending work, which fuses traditional industrial beats and vocals with drum n bass, sampling and heavy metal to create...
(bluish) discoloration on the head, giving rise to the common name of the disease, "blackhead".
Poultry
Poultry
Poultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...
(especially free-ranging
Free range
thumb|250px|Free-range chickens being fed outdoors.Free range is a term which outside of the United States denotes a method of farming husbandry where the animals are allowed to roam freely instead of being contained in any manner. In the United States, USDA regulations apply only to poultry and...
) 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 aren't removed or medicated by their owner, and they don't die or stop eating/defecating. H. gallinarum eggs can remain infective in soil for four years, thus there is a high risk of transmitting blackhead to turkeys if they graze areas with chicken 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 time frame.
The most common symptom of blackhead disease is yellow watery bird droppings. To reduce the spreading of the disease, sick birds must be removed and their litter changed.