''Heterakis gallinarum'' is a

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

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 has ...

that lives in the

cecum The cecum or caecum is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix (anatomy), appendix, to which i ...

of some

galliform Galliformes is an order of heavy-bodied ground-feeding birds that includes turkeys, chickens, quail, and other landfowl. Gallinaceous birds, as they are called, are important in their ecosystems as seed dispersers and predators, and are often ...

birds, particularly in ground feeders such as domestic

chicken 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 ...

s and

turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a list of transcontinental countries, transcontinental country located mainly on the Anatolia, Anatolian Peninsula in Western Asia, with ...

s. It causes infection that is mildly

pathogenic In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

. However, it often carries 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 parasite ''

Histomonas meleagridis ''Histomonas meleagridis'' is a species of parasitic protozoan that infects a wide range of birds including chickens, turkeys, peafowl, quail and pheasants, causing infectious enterohepatitis, or histomoniasis (blackhead diseases). ''H. meleagr ...

'' which causes of histomoniasis (blackhead disease). Transmission of ''H. meleagridis'' is through the ''H. gallinarum'' egg. ''H. gallinarum'' is about 1–2 cm in length with a sharply pointed tail and a preanal sucker. The parasite is a

diecious Plant reproductive morphology is the study of the physical form and structure (the morphology) of those parts of plants directly or indirectly concerned with sexual reproduction. Among all living organisms, flowers, which are the reproductive st ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

with marked

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

. Males are smaller and shorter, measuring around 9 mm in length, with a unique bent tail. Females are stouter and longer, measuring roughly 13 mm in length, with a straight tail end.Permin A & Hansen JW (1998)
''The Epidemiology, Diagnosis and Control of Poultry Parasites''
Food and Agriculture Organization of the United Nations, Rome, Italy, pp. 29–30.

Lifecycle

''H. gallinarum'' has a direct

lifecycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia * Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring *Life-cycle hypothesis ...

involving

birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

such as

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 ...

turkeys The turkey is a large bird in the genus ''Meleagris'', native to North America. There are two extant turkey species: the wild turkey (''Meleagris gallopavo'') of eastern and central North America and the ocellated turkey (''Meleagris ocellat ...

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 t ...

geese A goose (plural, : geese) is a bird of any of several waterfowl species in the family (biology), family Anatidae. This group comprises the genera ''Anser (bird), Anser'' (the grey geese and white geese) and ''Branta'' (the black geese). Some o ...

grouse Grouse are a group of birds from the order Galliformes, in the family Phasianidae. Grouse are presently assigned to the tribe Tetraonini (formerly the subfamily Tetraoninae and the family Tetraonidae), a classification supported by mitochondr ...

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 o ...

partridges A partridge is a medium-sized galliform bird in any of several genera, with a wide native distribution throughout parts of Europe, Asia and Africa. Several species have been introduced to the Americas. They are sometimes grouped in the Perdic ...

pheasants Pheasants ( ) are birds of several genera within the family Phasianidae in the order Galliformes. Although they can be found all over the world in introduced (and captive) populations, the pheasant genera native range is restricted to Eurasi ...

, and

quails Quail is a collective name for several genera of mid-sized birds generally placed in the order Galliformes. The collective noun for a group of quail is a flock, covey, or bevy. Old World quail are placed in the family Phasianidae, and New Wor ...

definitive host In biology and medicine, a host is a larger organism that harbours a smaller organism; whether a parasitic, a mutualistic, or a commensalist ''guest'' (symbiont). The guest is typically provided with nourishment and shelter. Examples include a ...

s. Eggs of ''H. gallinarum'' are passed in

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 relati ...

by the host. At optimal temperature (22 °C), they become infective in 12–14 days and remain infective for years in soil. Upon ingestion by a host, the embryonated eggs hatch into second-stage juveniles in the

gizzard The gizzard, also referred to as the ventriculus, gastric mill, and gigerium, is an organ found in the digestive tract of some animals, including archosaurs (pterosaurs, crocodiles, alligators, dinosaurs, birds), earthworms, some gastropods, so ...

duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...

, and are passed to the

. Their development is completed in the lumen, but some may enter 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 is ...

and remain for years without further development. The prepatent time is 24–30 days.

Earthworms 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. Th ...

and

houseflies The housefly (''Musca domestica'') is a fly of the suborder Cyclorrhapha. It is believed to have evolved in the Cenozoic Era, possibly in the Middle East, and has spread all over the world as a commensal of humans. It is the most common f ...

are considered paratenic hosts, as they can ingest the egg in feces and a juvenile may hatch in tissues, which stays dormant until eaten by

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

Epidemiology

''H. gallinarum'' is geographically distributed worldwide, commonly found in chickens,

domesticated turkey The domestic turkey (Meleagris gallopavo domesticus) is a large fowl, one of the two species in the genus '' Meleagris'' and the same species as the wild turkey. Although turkey domestication was thought to have occurred in central Mesoamerica a ...

s, and many other species of

fowl Fowl are birds belonging to one of two biological orders, namely the gamefowl or landfowl (Galliformes) and the waterfowl (Anseriformes). Anatomical and molecular similarities suggest these two groups are close evolutionary relatives; together ...

, primarily of

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, quails, a ...

. Their eggs are found to live for years in soil making it difficult to eliminate ''H. gallinarum'' from a domestic flock. Earthworms may ingest the eggs of ''H. gallinarum'' and contribute to the cause of infections in poultry. Although the eggs are themselves infective, they can develop further into a second infective

larval A larva (; plural larvae ) 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. The l ...

stage. This development occurs around 27 °C and takes 2–4 weeks.

Pathogenesis

''H. gallinarum'' infection is itself is mildly

. However, ''H. gallinarum'' plays the role of carrier in the lifecycle of ''

'', the causal

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

of enterohepatitis "blackhead" of turkeys. ''H. meleagridis'' stays viable while inside the egg of ''H. gallinarum''.Pattison M, McMullin P, Bradbury JM, Alexander D (2007)
''Poultry Diseases''
6th ed. Saunders Ltd, Philadelphia, Pennsylvania, p. 623. Heavy infection in pheasants indicated gross lesions characterized by congestion, thickening, petechial haemorrhages of the

, intussusception, and nodules in the cecal wall. In addition under

microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...

, chronic diffuse

typhlitis Neutropenic enterocolitis is inflammation of the cecum (part of the large intestine) that may be associated with infection. It is particularly associated with neutropenia, a low level of neutrophil, neutrophil granulocytes (the most common form of ...

, haemosiderosis,

granulomas A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectious ...

with

necrotic 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 dige ...

center in the

submucosa The submucosa (or tela submucosa) is a thin layer of tissue (biology), tissue in various organ (anatomy), organs of the gastrointestinal tract, gastrointestinal, respiratory tract, respiratory, and genitourinary system, genitourinary tracts. It i ...

and leiomyomas in the

muscular Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle ...

and

serosa The serous membrane (or serosa) is a smooth tissue membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces. The serous membrane ...

associated with immature ''H. gallinarum'' worms were observed.

Diagnosis and treatment

Primary infections are usually not apparent. Secondary infections are characterized by the formation of nodules in the cecum and the sub

of the cecum. During heavy infections, intestinal walls may thicken and exhibit marked

inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...

. In egg-laying hens, heavy infection significantly reduces egg production. Diagnosis commonly is through the presence of eggs in host feces. Effective treatment is by using

mebendazole Mebendazole (MBZ), sold under the brand name Vermox among others, is a medication used to treat a number of parasitic worm infestations. This includes ascariasis, pinworm infection, hookworm infections, guinea worm infections, hydatid disease, ...

, which is normally distributed to a flock of birds in their food and water. In addition, rearing the birds on hardware cloth assists in the elimination this

. Free-range chickens can also be infected.

References

External links

Zipcodezoo

BioLib

Information at Animal Diversity Web

Classification in Encyclopedia of Life

Taxonomy at UniProt
{{DEFAULTSORT:Heterakis Gallinarum Ascaridida Parasitic nematodes of vertebrates Parasites of birds Parasitic diseases Taxa named by Franz von Paula Schrank Animals described in 1788