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90-406: A/H5N1 virus is shed in the saliva, mucus, and feces of infected birds; other infected animals may shed bird flu viruses in respiratory secretions and other body fluids (such as milk). The virus can spread rapidly through poultry flocks and among wild birds. An estimated half billion farmed birds have been slaughtered in efforts to contain the virus. Symptoms of A/H5N1 influenza vary according to both

180-540: A chick , as in William Shakespeare 's play Macbeth , where Macduff laments the death of "all my pretty chickens and their dam". The usage is preserved in placenames such as the Hen and Chicken Islands . In older sources, and still often in trade and scientific contexts, chickens as a species are described as common fowl or domestic fowl . Chickens are relatively large birds , active by day . The body

270-521: A mutation that causes extra feathering under the face, giving the appearance of a beard. Chickens are omnivores . In the wild, they scratch at the soil to search for seeds, insects, and animals as large as lizards , small snakes, and young mice . A chicken may live for 5–10 years, depending on the breed . The world's oldest known chicken lived for 16 years. Chickens are gregarious , living in flocks , and incubate eggs and raise young communally. Individual chickens dominate others, establishing

360-412: A pecking order ; dominant individuals take priority for access to food and nest sites. The concept of dominance, involving pecking, was described in female chickens by Thorleif Schjelderup-Ebbe in 1921 as the "pecking order". Male chickens tend to leap and use their claws in conflicts. Chickens are capable of mobbing and killing a weak or inexperienced predator, such as a young fox. A male's crowing

450-472: A zoonotic event. As of June 2024, there is concern about two subtypes of avian influenza which are circulating in wild bird populations worldwide, A/H5N1 and A/H7N9 . Both of these have potential to devastate poultry stocks, and both have jumped to humans with relatively high case fatality rates . A/H5N1 in particular has infected a wide range of mammals and may be adapting to mammalian hosts. The Global Influenza Surveillance and Response System (GISRS)

540-470: A Spanish mink farm showed evidence of being the first recorded case of mammal-to-mammal transmission, with 4 percent of the farm's mink population dying from H5N1-related haemorrhagic pneumonia. This coincided with H5N1 detections in the area among gulls and other seabirds, which are the presumed source of the outbreak. A mass Caspian seal die-off in December 2022, with 700 infected seals found dead along

630-564: A cellular membrane to their lipid bilayer membrane. Priming by proteolytic processing, either of the fusion protein or of a companion protein, is necessary for the majority of viral fusion proteins. The priming stage then gets the fusion protein ready for triggering by the processes that go along with attachment and uptake, which frequently happens during transport of the fusion protein to the cell surface but may also happen extracellularly. So far, structural studies have revealed two kinds of viral fusion proteins. These proteins are believed to catalyze

720-463: A decline in GnRH-I-N. Hens often try to lay in nests that already contain eggs and sometimes move eggs from neighbouring nests into their own. A flock thus uses only a few preferred locations, rather than having a different nest for every bird. Under natural conditions, most birds lay only until a clutch is complete; they then incubate all the eggs. This is called "going broody ". The hen sits on

810-430: A factor in determining longevity of a virus on inanimate surfaces. Enveloped viruses possess great adaptability and can change in a short time in order to evade the immune system. Enveloped viruses can cause persistent infections . Vaccination against enveloped viruses can function by neutralizing the glycoprotein activity with antibodies. Eliminating the virus's ability to form an envelope—by removing or inactivating

900-464: A few people. All subtypes of avian Influenza A have potential to cross the species barrier, with H5N1 and H7N9 considered the biggest threats. In order to avoid infection, the general public are advised to avoid contact with sick birds or potentially contaminated material such as carcasses or feces. People working with birds, such as conservationists or poultry workers, are advised to wear appropriate personal protection equipment. Other animals –

990-542: A few people. All subtypes of avian Influenza A have potential to cross the species barrier, with H5N1 and H7N9 considered the biggest threats. In order to avoid infection, the general public are advised to avoid contact with sick birds or potentially contaminated material such as carcasses or feces. People working with birds, such as conservationists or poultry workers, are advised to wear appropriate personal protection equipment. The avian influenza hemagglutinin prefers to bind to alpha-2,3 sialic acid receptors, while

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1080-426: A gene for yellow skin, for instance, was incorporated into domestic birds from the grey junglefowl ( G. sonneratii ). It is estimated that chickens share between 71 and 79% of their genome with red junglefowl. According to one early study, a single domestication event of the red junglefowl in present-day Thailand gave rise to the modern chicken with minor transitions separating the modern breeds. The red junglefowl

1170-507: A greater affinity for oxygen, binding oxygen more readily. Fertile chicken eggs hatch at the end of the incubation period, about 21 days; the chick uses its egg tooth to break out of the shell. Hens remain on the nest for about two days after the first chick hatches; during this time the newly hatched chicks feed by absorbing the internal yolk sac . The hen guards her chicks and broods them to keep them warm. She leads them to food and water and calls them towards food. The chicks imprint on

1260-467: A hen (a circle dance), often lowering the wing which is closest to the hen. The dance triggers a response in the hen and when she responds to his call, the rooster may mount the hen and proceed with the mating. Mating typically involves a sequence in which the male approaches the female and performs a waltzing display. If the female is unreceptive, she runs off; otherwise, she crouches, and the male mounts, treading with both feet on her back. After copulation

1350-406: A large reservoir in wild waterfowl, which can infect the respiratory and gastrointestinal tract without affecting the health of the host. They can then be carried by the bird over large distances especially during annual migration. Infected birds can shed avian influenza A viruses in their saliva, nasal secretions, and feces; susceptible birds become infected when they have contact with the virus as it

1440-752: A mosaic of divergent ancestries inherited from subspecies of red junglefowl. A word for the domestic chicken ( *manuk ) is part of the reconstructed Proto-Austronesian language , indicating they were domesticated by the Austronesian peoples since ancient times. Chickens, together with dogs and pigs, were carried throughout the entire range of the prehistoric Austronesian maritime migrations to Island Southeast Asia , Micronesia , Island Melanesia , Polynesia , and Madagascar , starting from at least 3000 BC from Taiwan . These chickens might have been introduced during pre-Columbian times to South America via Polynesian seafarers, but evidence for this

1530-530: A number of scientists expressed concerns with the risks of creating novel potential pandemic pathogens, culminating in the formation of the Cambridge Working Group , a consensus statement calling for an assessment of the risks and benefits of such research. Research Institute for Biological Safety Problems (RIBSP), Zhambyl Region, Republic of Kazakhstan. Chicken Gallus domesticus L. The chicken ( Gallus domesticus )

1620-452: A protein shell known as the capsid, from the Latin capsa, meaning "box," in order to shield it from this hostile environment. Similar to how numerous bricks come together to form a wall, the capsid is made up of one or more distinct protein types that repeatedly repeat to form the whole capsid. This repetitive pattern creates a robust but rather flexible capsid. The nucleic acid inside the capsid

1710-454: A result, flaviviruses and pseudo typed retroviruses have a harder time infecting TAM-deficient DCs, albeit infection can be brought back by type I IFN antibodies. A TAM kinase inhibitor, meanwhile, prevents infection of wild-type DCs. TAM receptors, which are potential targets for therapy, are thereby activated by viruses to reduce type I IFN signaling. Glycoproteins on the surface of the envelope serve to identify and bind to receptor sites on

1800-651: A sacred rooster, often during a ritual cockfight , used as a form of communication with the gods. In Gabriel García Márquez 's Nobel-Prize-winning 1967 novel One Hundred Years Of Solitude , cockfighting is outlawed in the town of Macondo after the patriarch of the Buendia family murders his cockfighting rival and is haunted by the man's ghost. Chicken jokes have been made at least since The Knickerbocker published one in 1847. Chickens have been featured in art in farmyard scenes such as Adriaen van Utrecht 's 1646 Turkeys and Chickens and Walter Osborne 's 1885 Feeding

1890-400: A significant drop in egg production, and sudden death. In mammals, including humans, A/H5N1 influenza (whether LPAI or HPAI) is rare. Symptoms of infection vary from mild to severe, including fever, diarrhoea, and cough. Human infections with A/H5N1 virus have been reported in 23 countries since 1997, resulting in severe pneumonia and death in about 50% of cases. Between 2003 and November 2024,

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1980-485: A single domestication event of red junglefowl whose present-day distribution is predominantly in southwestern China, northern Thailand and Myanmar. These domesticated chickens spread across Southeast and South Asia where they interbred with local wild species of junglefowl, forming genetically and geographically distinct groups. Analysis of the most popular commercial breed shows that the White Leghorn breed possesses

2070-683: A special issue of the journal Science devoted to H5N1. The papers by Fouchier and Kawaoka conclude that it is entirely possible that a natural chain of mutations could lead to an H5N1 virus acquiring the capability of airborne transmission between mammals, and that a H5N1 influenza pandemic would not be impossible. In May 2013, it was reported that scientists at the Harbin Veterinary Research Institute in Harbin , China, had created H5N1 strains which passed between guinea pigs . In response to Fouchier and Kawaoka's work,

2160-400: A specific isolate of virus, researchers use the internationally accepted Influenza virus nomenclature, which describes, among other things, the species of animal from which the virus was isolated, and the place and year of collection. For example, A/chicken/Nakorn-Patom/Thailand/CU-K2/04(H5N1) : Other examples include: A/duck/Hong Kong/308/78(H5N3), and A/shoveler/Egypt/03(H5N2). H5N1 is

2250-410: A subtype of Influenza A virus. Like all subtypes it is an enveloped negative-sense RNA virus , with a segmented genome . Subtypes of IAV are defined by the combination of the antigenic hemagglutinin and neuraminidase proteins in the viral envelope . "H5N1" designates an IAV subtype that has a type 5 hemagglutinin (H) protein and a type-1 neuraminidase (N) protein. Further variations exist within

2340-564: A vector for bacterial diseases such as salmonellosis and spirochaetosis . Viral diseases include avian influenza . Chickens are common and widespread domestic animals, with a total population of 23.7 billion as of 2018 . More than 50 billion chickens are reared annually as a source of meat and eggs. In the United States alone, more than 8 billion chickens are slaughtered each year for meat, and more than 300 million chickens are reared for egg production. The vast majority of poultry

2430-411: A very long time, it was thought that the spike proteins, which are necessary for infectivity, were directly incorporated into the viral core through their cytoplasmic domains. Recent research suggests that while such direct interactions may be what causes the budding of alphaviruses, this may not be the case for retroviruses and negative strand RNA viruses . These viruses can form bud particles even in

2520-488: A virus buds often dies or is weakened, and sheds more viral particles for an extended period. The lipid bilayer envelope of these viruses is relatively sensitive to desiccation , heat, and amphiphiles such as soap and detergents , therefore these viruses are easier to sterilize than non-enveloped viruses, have limited survival outside host environments, and typically must transfer directly from host to host. Viral envelope persistence, whether it be enveloped or naked, are

2610-452: A wide range of other animals have been affected by avian flu, generally due to eating birds which had been infected. There have been instances where transmission of the disease between mammals, including seals and cows, may have occurred. Many more outbreaks are recorded, in almost every country in the world, affecting both wild birds and poultry, with occasional spillover events infecting humans. In October 2022 an outbreak of H5N1 on

2700-617: Is a contest held in a ring called a cockpit between two cocks. Cockfighting is outlawed in many countries as involving cruelty to animals . The activity seems to have been practised in the Indus Valley civilisation from 2500 to 2100 BC. In the process of domestication, chickens were apparently kept initially for cockfighting, and only later used for food. Chickens have long been used as model organisms to study developing embryos. Large numbers of embryos can be provided commercially; fertilized eggs can easily be opened and used to observe

2790-616: Is a global network of laboratories that monitor the spread of influenza with the aim to provide the World Health Organization with influenza control information and to inform vaccine development. Several millions of specimens are tested by the GISRS network annually through a network of laboratories in 127 countries. GISRS monitors avian, swine, and other potentially zoonotic influenza viruses as well as human viruses. Birds – Influenza A viruses of various subtypes have

Influenza A virus subtype H5N1 - Misplaced Pages Continue

2880-604: Is a large and round short-winged bird , domesticated from the red junglefowl of Southeast Asia around 8,000 years ago. Most chickens are raised for food, providing meat and eggs ; others are kept as pets or for cockfighting . Chickens are common and widespread domestic animals, with a total population of 26.5 billion as of 2023 , and an annual production of more than 50 billion birds. A hen bred for laying can produce over 300 eggs per year. There are numerous cultural references to chickens in folklore, religion, and literature. Terms for chickens include: Chicken can mean

2970-409: Is a loud and sometimes shrill call, serving as a territorial signal to other males, and in response to sudden disturbances within their surroundings. Hens cluck loudly after laying an egg and to call their chicks. Chickens give different warning calls to indicate that a predator is approaching from the air or on the ground. To initiate courting, some roosters may dance in a circle around or near

3060-551: Is a mandatory vaccination requirement since 2017; the vaccine is bivalent or trivalent, targeting the H5 and H7 subtypes of influenza A virus. It is manufactured using recombinant influenza virus. In the event of an outbreak of human H5N1, the main antiviral drugs recommended are neuraminidase inhibitors , such as zanamivir (Relenza) and oseltamivir (Tamiflu) . These drugs can reduce the severity of symptoms if taken soon after infection and can also be taken as prophylaxis to decrease

3150-422: Is appropriately protected by its modest size and physical difficulty in opening it. The nucleocapsid of the virion is made up of the nucleic acid and the capsid. Remember that the genomes of most viruses are very small. Genes code for instructions to make proteins, so small genomes cannot code for many proteins. Therefore, the virion capsid consists of one or only a few proteins that repeat over and over  to form

3240-427: Is characteristic of RNA viruses . The segmentation of the influenza A virus genome facilitates genetic recombination by segment reassortment in hosts who become infected with two different strains of influenza viruses at the same time. With reassortment between strains, an avian strain which does not affect humans may acquire characteristics from a different strain which enable it to infect and pass between humans –

3330-677: Is detected in poultry, it is normal to cull infected animals and those nearby in an effort to rapidly contain, control and eradicate the disease. This is done together with movement restrictions, improved hygiene and biosecurity, and enhanced surveillance. Humans – Avian flu viruses, both HPAI and LPAI, can infect humans who are in close, unprotected contact with infected poultry. Incidents of cross-species transmission are rare, with symptoms ranging in severity from no symptoms or mild illness, to severe disease that resulted in death. As of February 2024, there have been very few instances of human-to-human transmission, and each outbreak has been limited to

3420-463: Is glycoprotein. They have been shown to play significant roles in immunity and infection. Viral glycoproteins, a new class of cellular inhibitory proteins has been discovered. These include the E3 ubiquitin ligases of the membrane-associated RING-CH (MARCH) family, which among other things, inhibits the expression of cell surface proteins implicated in adaptive immunity. Being made up mostly of host membrane,

3510-592: Is inhumane towards sentient animals . Advocates of intensive farming say that their efficient systems save land and food resources owing to increased productivity, and that the animals are looked after in a controlled environment. Chickens farmed for meat are called broilers . Broiler breeds typically take less than six weeks to reach slaughter size, some weeks longer for free range and organic broilers. Chickens farmed primarily for eggs are called layer hens. The UK alone consumes more than 34 million eggs per day. Hens of some breeds can produce over 300 eggs per year;

3600-434: Is no preventative or curative medicine for the majority of them. In most cases, the known vaccines operate by inducing antibodies that prevent the pathogen from entering cells. This happens in the case of enveloped viruses when the antibodies bind to the viral envelope proteins. The membrane fusion event that triggers viral entrance is caused by the viral fusion protein . Many enveloped viruses only have one protein visible on

3690-630: Is potential for low pathogenic avian influenza viruses (LPAI) to evolve into strains which are high pathogenic to poultry (HPAI), and subsequent potential for significant illness and death among poultry during outbreaks. Because of this, international regulations state that any detection of H5 or H7 subtypes (regardless of their pathogenicity) must be notified to the appropriate authority. It is also possible that avian influenza viruses could be transmitted to humans and other animals which have been exposed to infected birds, causing infection with unpredictable but sometimes fatal consequences. When an HPAI infection

Influenza A virus subtype H5N1 - Misplaced Pages Continue

3780-477: Is raised in factory farms . According to the Worldwatch Institute , 74% of the world's poultry meat and 68% of eggs are produced this way. An alternative to intensive poultry farming is free-range farming. Friction between these two main methods has led to long-term issues of ethical consumerism . Opponents of intensive farming argue that it harms the environment, creates human health risks and

3870-489: Is round, the legs are unfeathered in most breeds, and the wings are short. Wild junglefowl can fly ; chickens and their flight muscles are too heavy to allow them to fly more than a short distance. Size and coloration vary widely between breeds. Adult chickens of both sexes have a fleshy crest on their heads called a comb or cockscomb, and hanging flaps of skin on either side under their beaks called wattles ; combs and wattles are more prominent in males . Some breeds have

3960-486: Is shed by infected birds. The virus can survive for long periods in water and at low temperatures, and can be spread from one farm to another on farm equipment. Domesticated birds (chickens, turkeys, ducks, etc.) may become infected with avian influenza A viruses through direct contact with infected waterfowl or other infected poultry, or through contact with contaminated feces or surfaces. Avian influenza outbreaks in domesticated birds are of concern for several reasons. There

4050-687: Is still putative. The possibility that domestic chickens were in the Americas before Western contact is debated by researchers, but blue-egged chickens, found only in the Americas and Asia, suggest an Asian origin for early American chickens. A lack of data from Thailand, Russia, the Indian subcontinent, Southeast Asia and Sub-Saharan Africa makes it difficult to lay out a clear map of the spread of chickens in these areas; better description and genetic analysis of local breeds threatened by extinction may also help with research into this area. Chicken bones from

4140-524: Is supplemented by mentions in historical texts from the last few centuries BC, and by depictions in prehistoric artworks, such as across Central Asia. Chickens were widespread throughout southern Central Asia by the 4th century BC. Middle Eastern chicken remains go back to a little earlier than 2000 BC in Syria . Phoenicians spread chickens along the Mediterranean coasts as far as Iberia. During

4230-426: Is well adapted to take advantage of the vast quantities of seed produced during the end of the multi-decade bamboo seeding cycle , to boost its own reproduction. In domesticating the chicken, humans took advantage of the red junglefowl's ability to reproduce prolifically when exposed to a surge in its food supply. Exactly when and where the chicken was domesticated remains controversial. Genomic studies estimate that

4320-553: The Arauco Peninsula in south-central Chile were radiocarbon dated as pre-Columbian, and DNA analysis suggested they were related to prehistoric populations in Polynesia. However, further study of the same bones cast doubt on the findings. Chicken remains have been difficult to date, given the small and fragile bird bones; this may account for discrepancies in dates given by different sources. Archaeological evidence

4410-489: The Caspian Sea coastline of Russia's Dagestan republic , worried researchers regarding the possibility that wild mammal-to-mammal spread had begun. A similar mass die-off of 95% of southern elephant seal pups in 2023 also raised concerns of mammal-to-mammal spread, as nursing pups would have had less exposure to birds. Between January and October 2023, at least 24,000 South American sea lions died from H5N1 flu, with

4500-637: The Galliformes , the order of bird that chickens belong to, survived the Cretaceous–Paleogene extinction event that killed all tree-dwelling birds and their dinosaur relatives. Chickens are descended primarily from the red junglefowl ( Gallus gallus ) and are scientifically classified as the same species. Domesticated chickens freely interbreed with populations of red junglefowl. The domestic chicken has subsequently hybridised with grey junglefowl , Sri Lankan junglefowl and green junglefowl ;

4590-631: The Hellenistic period (4th–2nd centuries BC), in the southern Levant , chickens began to be widely domesticated for food. The first pictures of chickens in Europe are found on Corinthian pottery of the 7th century BC. Breeding increased under the Roman Empire and reduced in the Middle Ages . Genetic sequencing of chicken bones from archaeological sites in Europe revealed that in

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4680-788: The High Middle Ages chickens became less aggressive and began to lay eggs earlier in the breeding season. Chickens reached Egypt via the Middle East for purposes of cockfighting about 1400 BC and became widely bred in Egypt around 300 BC. Three possible routes of introduction into Africa around the early first millennium AD could have been through the Egyptian Nile Valley, the East Africa Roman-Greek or Indian trade, or from Carthage and

4770-417: The World Health Organization has recorded 948 cases of confirmed H5N1 influenza, leading to 464 deaths. The true fatality rate may be lower because some cases with mild symptoms may not have been identified as H5N1. A/H5N1 influenza virus was first identified in farmed birds in southern China in 1996. Between 1996 and 2018, A/H5N1 coexisted in bird populations with other subtypes of the virus, but since then,

4860-541: The ligands Gas6 and Protein S . The phospholipid phosphatidylserine may be seen on the membranes of several enveloped viruses, which they employ to bind Gas6 and Protein S to activate TAM receptors. Ligand-coated viruses stimulate type I IFN signaling, activate TAM receptors on dendritic cells (DCs), and suppress type II interferon signaling to circumvent host defenses and advance infection.TAM-deficient DCs exhibit type I IFN responses that are more pronounced than those of wild-type cells in response to viral exposure. As

4950-533: The Berbers, across the Sahara . The earliest known remains are from Mali , Nubia , East Coast, and South Africa and date back to the middle of the first millennium AD. Chickens are susceptible both to parasites such as mites , and to diseases caused by pathogens such as bacteria and viruses . The parasite Dermanyssus gallinae feeds on blood, causing irritation and reducing egg production, and acts as

5040-550: The Chickens . The nursery rhyme " Cock a doodle doo ", its chorus line imitating the cockerel's call, was published in Mother Goose's Melody in 1765. The 2000 animated adventure comedy film Chicken Run , directed by Peter Lord and Nick Park , featured anthropomorphic chickens with many chicken jokes. Viral envelope A viral envelope is the outermost layer of many types of viruses . It protects

5130-500: The H5N1 subtype which is considered the biggest risk among subtypes. However, because the influenza virus is highly variable, any vaccine needs to be specifically targeted against the particular strain of virus which is causing concern. Existing influenza vaccine technologies can be adapted to a H5N1 strain causing the pandemic; in the event of an outbreak, the candidate vaccine would be rapidly tested for safety as well as efficacy against

5220-482: The UK and Europe, laying hens are then slaughtered and used in processed foods, or sold as 'soup hens'. In some other countries, flocks are sometimes force moulted rather than being slaughtered to re-invigorate egg-laying. This involves complete withdrawal of food (and sometimes water) for 7–14 days or sufficiently long to cause a body weight loss of 25 to 35%, or up to 28 days under experimental conditions. This stimulates

5310-617: The absence of spike proteins by relying only on viral core components. The spike proteins can occasionally be produced as virus-like particles without the viral core. Therefore, optimal budding and release may be dependent on a coordinated "push-and-pull" action between core and spike, where oligomerization of both components is essential. They may help viruses avoid the host immune system . TAM receptor tyrosine kinases increase phagocytic clearance of apoptotic cells and inhibit immunological responses brought on by Toll-like receptors and type I interferons (IFNs) when they are activated by

5400-425: The chicken genome is similarly sized compared to other birds, but smaller than nearly all mammals: the human genome is 3.2 Gb . The final gene set contained 26,640 genes (including noncoding genes and pseudogenes ), with a total of 19,119 protein-coding genes, a similar number to the human genome. In 2006, scientists researching the ancestry of birds switched on a chicken recessive gene , talpid2 , and found that

5490-463: The chicken was domesticated 8,000 years ago in Southeast Asia and spread to China and India 2,000 to 3,000 years later. Archaeological evidence supports domestic chickens in Southeast Asia well before 6000 BC, China by 6000 BC and India by 2000 BC. A landmark 2020 Nature study that fully sequenced 863 chickens across the world suggests that all domestic chickens originate from

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5580-446: The developing embryo. Equally important, embryologists can carry out experiments on such embryos, close the egg again and study the effects later in development. For instance, many important discoveries in limb development have been made using chicken embryos, such as the discovery of the apical ectodermal ridge and the zone of polarizing activity . The chicken was the first bird species to have its genome sequenced. At 1.21 Gb ,

5670-406: The embryo jaws initiated formation of teeth, like those found in ancient bird fossils. Chickens are featured widely in folklore , religion , literature , and popular culture. The chicken is a sacred animal in many cultures and deeply embedded in belief systems and religious practices. Roosters are sometimes used for divination , a practice called alectryomancy. This involves the sacrifice of

5760-500: The genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. A viral envelope protein or E protein is a protein in the envelope, which may be acquired by the capsid from an infected host cell. Numerous human pathogenic viruses in circulation are encased in lipid bilayers , and they infect their target cells by causing the viral envelope and cell membrane to fuse. Although there are effective vaccines against some of these viruses, there

5850-490: The hen and subsequently follow her continually. She continues to care for them until they are several weeks old. Inbreeding of White Leghorn chickens tends to cause inbreeding depression expressed as reduced egg number and delayed sexual maturity. Strongly inbred Langshan chickens display obvious inbreeding depression in reproduction, particularly for traits such as age when the first egg is laid and egg number. Water or ground-dwelling fowl similar to modern partridges , in

5940-952: The hen to lose her feathers but also re-invigorates egg-production. Some flocks may be force-moulted several times. In 2003, more than 75% of all flocks were moulted in the US. Keeping chickens as pets became increasingly popular in the 2000s among urban and suburban residents. Many people obtain chickens for their egg production but often name them and treat them as any other pet like cats or dogs. Chickens provide companionship and have individual personalities. While many do not cuddle much, they will eat from one's hand, jump onto one's lap, respond to and follow their handlers, as well as show affection. Chickens are social, inquisitive, intelligent birds, and many people find their behaviour entertaining. Certain breeds, such as silkies and many bantam varieties, are generally docile and are often recommended as good pets around children with disabilities. A cockfight

6030-487: The high lethality and virulence of HPAI A(H5N1), its worldwide presence, its increasingly diverse host reservoir , and its significant ongoing mutations, the H5N1 virus is regarded as the world's largest pandemic threat. Domestic poultry may potentially be protected from specific strains of the virus by vaccination. In the event of a serious outbreak of H5N1 flu among humans, health agencies have prepared "candidate" vaccines that may be used to prevent infection and control

6120-418: The highest authenticated rate of egg laying is 371 eggs in 364 days. After 12 months of laying, the commercial hen's egg-laying ability declines to the point where the flock is commercially unviable. Hens, particularly from battery cage systems, are sometimes infirm or have lost a significant amount of their feathers, and their life expectancy has been reduced from around seven years to less than two years. In

6210-408: The highly pathogenic subtype HPAI A(H5N1) has become the dominant strain in bird populations worldwide. Some strains of A/H5N1 which are highly pathogenic to chickens have adapted to cause mild symptoms in ducks and geese, and are able to spread rapidly through bird migration. Mammal species in addition to humans that have been recorded with H5N1 infection include cows, seals, goats, and skunks. Due to

6300-419: The host cell. There are three main types of viral glycoproteins: Envelope proteins, membrane proteins, and spike proteins (E, M, and S). The viral envelope then fuses with the host's membrane, allowing the capsid and viral genome to enter and infect the host. All enveloped viruses also have a capsid , another protein layer, between the envelope and the genome. The virus wraps its delicate nucleic acid with

6390-441: The host's membrane. The particular set of viral proteins are engaged in a series of structural changes. When these changes are set/finished, there is then and only then, fusion with the host membrane. These glycoproteins mediate the interaction between virion and host cell, typically initiating the fusion between the viral envelope and the host's cellular membrane. In some cases, the virus with an envelope will form an endosome within

6480-579: The human influenza hemagglutinin prefers to bind to alpha-2,6 sialic acid receptors. This means that when the H5N1 strain infects humans, it will replicate in the lower respiratory tract (where alpha-2,3 sialic acid receptors are more plentiful in humans) and consequently cause viral pneumonia . Between 2003 and November 2024, the World Health Organization has recorded 948 cases of confirmed H5N1 influenza, leading to 464 deaths. The true fatality rate may be lower because some cases with mild symptoms may not have been identified as H5N1. To unambiguously describe

6570-736: The leading academic journal Science , the US National Science Advisory Board for Biosecurity (NSABB) recommended against publication of the full details of the study, and the one submitted to Nature by Yoshihiro Kawaoka of the University of Wisconsin describing related work. However, after additional consultations at the World Health Organization and by the NSABB, the NSABB reversed its position and recommended publication of revised versions of

6660-627: The male does a tail-bending display. Sperm transfer occurs by cloacal contact between the male and female, in an action called the 'cloacal kiss'. As with all birds, reproduction is controlled by a neuroendocrine system, the Gonadotropin-Releasing Hormone-I neurons in the hypothalamus . Reproductive hormones including estrogen , progesterone , and gonadotropins ( luteinizing hormone and follicle-stimulating hormone ) initiate and maintain sexual maturation changes. Reproduction declines with age, thought to be due to

6750-616: The milk. Around 50% of cats that lived on the affected dairy farms and were fed unpasteurised milk from symptomatic cows died within a few days from severe systemic influenza infection, raising significant concerns of cross-species mammal-to-mammal transmission. Novel, contagious strains of H5N1 were created by Ron Fouchier of the Erasmus Medical Center in Rotterdam, the Netherlands, who first presented his work to

6840-462: The nest, fluffing up or pecking defensively if disturbed. She rarely leaves the nest until the eggs have hatched. Eggs of chickens from the high-altitude region of Tibet have special physiological adaptations that result in a higher hatching rate in low oxygen environments. When eggs are placed in a hypoxic environment, chicken embryos from these populations express much more hemoglobin than embryos from other chicken populations. This hemoglobin has

6930-570: The outbreak starting on the Pacific coast of Peru, moving down the coast to Chile and then up the Atlantic coast of Argentina. In April 2024, spread of H5N1 amongst dairy cow herds in nine states of the USA strongly indicated the presence of cow-to-cow transmission possibly occurring while the animals were being milked. Although mortality in bovines infected with H5N1 is rare, viable virus can be shed in

7020-485: The outbreak; however, it could take several months to ramp up mass production. Avian flu viruses, both HPAI and LPAI, can infect humans who are in close, unprotected contact with infected poultry. Incidents of cross-species transmission are rare, with symptoms ranging in severity from no symptoms or mild illness, to severe disease that resulted in death. As of February, 2024 there have been very few instances of human-to-human transmission, and each outbreak has been limited to

7110-557: The public at an influenza conference in Malta in September 2011. Three mutations were introduced into the H5N1 virus genome, and the virus was then passed from the noses of infected ferrets to the noses of uninfected ones, which was repeated 10 times. After these 10 passages the H5N1 virus had acquired the ability of transmission between ferrets via aerosols or respiratory droplets. After Fouchier offered an article describing this work to

7200-551: The risk of infection. Influenza A/H5N1 was first detected in 1959 after an outbreak of highly pathogenic avian influenza in Scotland, which infected two flocks of chickens. The next detection, and the earliest infection of humans by H5N1, was an epizootic (an epidemic in nonhumans) of H5N1 influenza in Hong Kong's poultry population in 1997. This outbreak was stopped by the killing of the entire domestic poultry population within

7290-420: The same mechanism in both situations, resulting in the fusing of two bilayers. In other words, these proteins operate as enzymes, which while having various structural variations catalyze the same chemical reaction. The envelopes are typically derived from portions of the host cell membranes ( phospholipids and proteins), but include some viral glycoproteins . One of the main parts of human pathogenic viruses

7380-516: The same time. Through a combination of mutation and genetic reassortment the virus can evolve to acquire new characteristics, enabling it to evade host immunity and occasionally to jump from one species of host to another. Humans – Several "candidate" (unproved) vaccines are available in case an avian virus acquires the ability to infect and transmit among humans; as of July 2024 these include Aflunov, Celldemic and Seqirus/Audenz. Some governments have prepared strategic stockpiles of vaccines against

7470-465: The strain of virus underlying the infection and on the species of bird or mammal affected. Classification as either Low Pathogenic Avian Influenza (LPAI) or High Pathogenic Avian Influenza (HPAI) is based on the severity of symptoms in domestic chickens and does not predict the severity of symptoms in other species. Chickens infected with LPAI A/H5N1 virus display mild symptoms or are asymptomatic , whereas HPAI A/H5N1 causes serious breathing difficulties,

7560-431: The structure. The viral nucleic acid  would be physically too large to fit inside the capsid if it consisted of more than  a few proteins. The capsid, having a focused role of protecting the genome in addition to immune recognition evasion. The viral capsid is known for its protection of RNA before it is inserted into the host cell, unlike the viral envelope which protects the protein capsid. The cell from which

7650-411: The subtypes and can lead to very significant differences in the virus's ability to infect and cause disease, as well as to the severity of symptoms. Influenza viruses have a relatively high mutation rate that is characteristic of RNA viruses . The segmentation of its genome facilitates genetic recombination by segment reassortment in hosts infected with two different strains of influenza viruses at

7740-470: The surface of the particle, which is required for both mediating adhesion to the cell surface and for the subsequent membrane fusion process. To create potentially protective vaccines for human pathogenic enveloped viruses for which there is currently no vaccine, it is essential to comprehend how antibodies interact with viral envelope proteins, particularly with the fusion protein, and how antibodies neutralize viruses. Enveloped viruses enter cells by joining

7830-423: The territory. Human infection was confirmed in 18 individuals who had been in close contact with poultry, 6 of whom died. Since then, avian A/H5N1 bird flu has become widespread in wild birds worldwide, with numerous outbreaks among both domestic and wild birds. An estimated half a billion farmed birds have been slaughtered in efforts to contain the virus. Influenza viruses have a relatively high mutation rate that

7920-472: The two papers. However, then the Dutch government declared that this type of manuscripts required Fouchier to apply for an export permit in the light of EU directive 428/2009 on dual use goods. After much controversy surrounding the publishing of his research, Fouchier complied (under formal protest) with Dutch government demands to obtain a special permit for submitting his manuscript, and his research appeared in

8010-418: The viral envelope can also have the proteins associated with the host cell within their membrane after budding. Many enveloped viruses mature by budding at the plasma membrane, which allows them to be discharged from infected cells. During this procedure, viral transmembrane proteins, also known as spike proteins , are integrated into membrane vesicles containing components of the viral core (capsid). For

8100-429: The zoonotic strain, and then authorised and distributed to vaccine manufacturers. Poultry – it is possible to vaccinate poultry against specific strains of HPAI influenza. Vaccination should be combined with other control measures such as infection monitoring, early detection and biosecurity. In many countries, it is routine to vaccinate poultry against H5N1. In China, the world's biggest poultry producer, there has been

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