Avian influenza, also known as avian flu, is a bird flu caused by the influenza A virus, which can infect people. It is similar to other types of animal flu in that it is caused by a virus strain that has adapted to a specific host. The type with the greatest risk is highly pathogenic avian influenza (HPAI).
Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus which can cause illness in humans and many other species. A bird-adapted strain of H5N1, called HPAI A(H5N1) for highly pathogenic avian influenza virus of type A of subtype H5N1, is the highly pathogenic causative agent of H5N1 flu, commonly known as avian influenza. It is enzootic in many bird populations, especially in Southeast Asia. One strain of HPAI A(H5N1) is spreading globally after first appearing in Asia. It is epizootic and panzootic, killing tens of millions of birds and spurring the culling of hundreds of millions of others to stem its spread. Many references to "bird flu" and H5N1 in the popular media refer to this strain.
In birds, the bursa of Fabricius is the site of hematopoiesis. It is a specialized organ that, as first demonstrated by Bruce Glick and later by Max Dale Cooper and Robert Good, is necessary for B cell development in birds. Mammals generally do not have an equivalent organ; the bone marrow is often the site of both hematopoiesis and B cell development. The bursa is present in the cloaca of birds and is named after Hieronymus Fabricius, who described it in 1621.
Carnivore protoparvovirus 1 is a species of parvovirus that infects carnivorans. It causes a highly contagious disease in both dogs and cats separately. The disease is generally divided into two major genogroups: FPV containing the classical feline panleukopenia virus (FPLV), and CPV-2 containing the canine parvovirus type 2 (CPV-2) which appeared in the 1970s.
Poultry diseases occur in poultry, which are domesticated birds kept for their meat, eggs or feathers. Poultry species include the chicken, turkey, duck, goose and ostrich.
Avian infectious bronchitis (IB) is an acute and highly contagious respiratory disease of chickens. The disease is caused by avian infectious bronchitis virus (IBV), a coronavirus, and characterized by respiratory signs including gasping, coughing, sneezing, tracheal rales, and nasal discharge. In young chickens, severe respiratory distress may occur. In layers, respiratory distress, nephritis, decrease in egg production, and loss of internal and external egg quality are reported.
Marek's disease is a highly contagious viral neoplastic disease in chickens. It is named after József Marek, a Hungarian veterinarian who described it in 1907. Marek's disease is caused by an alphaherpesvirus known as "Marek's disease virus" (MDV) or Gallid alphaherpesvirus 2 (GaHV-2). The disease is characterized by the presence of T cell lymphoma as well as infiltration of nerves and organs by lymphocytes. Viruses related to MDV appear to be benign and can be used as vaccine strains to prevent Marek's disease. For example, the related herpesvirus found in turkeys (HVT), causes no apparent disease in the birds, and continues to be used as a vaccine strain for prevention of Marek's disease.
Chicken anemia virus, or CAV, is currently a member of the Anelloviridae family which is found worldwide. The virus only affects chickens. CAV is a non-enveloped icosahedral single stranded DNA virus, which causes bone marrow atrophy, anemia, and severe immunosuppression. Clinical signs of CAV infection are predominantly found in young chicks due to vertical transmission from the breeder hens whose maternal antibodies have not yet formed following exposure. Clinical disease is rare today because of the widespread practice of vaccinating breeders, but the subclinical form of the disease—which normally affects birds more than two weeks of age following horizontal transmission of the virus via the fecal–oral route—is ubiquitous. The virus is very resistant in the environment, making elimination very difficult.
Influenza A virus subtype H7N7 (A/H7N7) is a subtype of Influenza A virus, a genus of Orthomyxovirus, the viruses responsible for influenza. Highly pathogenic strains (HPAI) and low pathogenic strains (LPAI) exist. H7N7 can infect humans, birds, pigs, seals, and horses in the wild; and has infected mice in laboratory studies. This unusual zoonotic potential represents a pandemic threat.
Astroviruses (Astroviridae) are a type of virus that was first discovered in 1975 using electron microscopes following an outbreak of diarrhea in humans. In addition to humans, astroviruses have now been isolated from numerous mammalian animal species and from avian species such as ducks, chickens, and turkey poults. Astroviruses are 28–35 nm diameter, icosahedral viruses that have a characteristic five- or six-pointed star-like surface structure when viewed by electron microscopy. Along with the Picornaviridae and the Caliciviridae, the Astroviridae comprise a third family of nonenveloped viruses whose genome is composed of plus-sense, single-stranded RNA. Astrovirus has a non-segmented, single stranded, positive sense RNA genome within a non-enveloped icosahedral capsid. Human astroviruses have been shown in numerous studies to be an important cause of gastroenteritis in young children worldwide. In animals, Astroviruses also cause infection of the gastrointestinal tract but may also result in encephalitis, hepatitis (avian) and nephritis (avian).
Fowlpox is the worldwide disease of poultry caused by viruses of the family Poxviridae and the genus Avipoxvirus. The viruses causing fowlpox are distinct from one another but antigenically similar, possible hosts including chickens, turkeys, quail, canaries, pigeons, and many other species of birds. There are two forms of the disease. The first is spread by biting insects and wound contamination, and causes lesions on the comb, wattles, and beak. Birds affected by this form usually recover within a few weeks. The second is contracted by inhalation or ingestion of the virus via dust or aerosols, leading to the 'diphtheritic form' of the disease, in which diphtheritic membranes form in the mouth, pharynx, larynx, and sometimes the trachea. The prognosis for this form is poor.
Influenza, commonly known as "the flu" or just "flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin from one to four days after exposure to the virus and last for about 2–8 days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia, which can be caused by the virus or by a subsequent bacterial infection. Other complications of infection include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.
Histomoniasis is a commercially significant disease of poultry, particularly of chickens and turkeys, due to parasitic infection of a protozoan, Histomonas meleagridis. The protozoan is transmitted to the bird by the nematode parasite Heterakis gallinarum. H. meleagridis resides within the eggs of H. gallinarum, so birds ingest the parasites along with contaminated soil or food. Earthworms can also act as a paratenic host.
Avian orthoreovirus, also known as avian reovirus, is an orthoreovirus from the Reoviridae family. Infection causes arthritis and tenosynovitis in poultry. It can also cause respiratory disease.
Avian metapneumovirus (aMPV), also known as turkey rhinotracheitis or swollen head syndrome, causes a variety of disease syndromes in birds, depending on the bird species and virus type.
Pacheco's disease is a highly infectious and acute bird disease caused by a species of herpesvirus, Psittacid alphaherpesvirus 1 (PsHV-1). All psittacine species are susceptible to Pacheco's disease, mainly those in zoological collections and aviaries in any geographic regions. Specifically, Pacheco's disease has a high occurrence rate in Amazon parrots, followed by African grey parrots, parrots, macaws, cockatoos and conures. Due to a very high mortality rate within these susceptible species, concerns are brought to companion bird markets and breeders.
Infectious pancreatic necrosis virus (IPNV) is a double-stranded RNA virus from the family Birnaviridae, in the genus Aquabirnavirus. Causing the highly infectious disease Infectious pancreatic necrosis, the virus primarily affects young salmonids resulting in high mortality, occasionally surpassing 90 percent in the early stages. IPNV or IPNV-like viruses have been isolated worldwide from at least 32 families of saltwater and freshwater salmonids and non-salmonids fish including salmon, flatfish, pike, eels and others. Other aquatic organisms infected include 11 molluscs and 4 species of crustaceans. Due to its wide host range and high mortality, the virus is of great concern to global aquaculture. In addition to persistence in hosts, IPNV is also perpetual in the environment, surviving across a range of conditions and capable of infecting fish with as little as 101TCID50/ml of the virus. Found in Europe, North America, South America, Africa, Asia, and Australia, the virus has led to significant losses in the mariculture of Atlantic salmon, brook trout, and rainbow trout.
The avian immune system is the system of biological structures and cellular processes that protects birds from disease.
Egg drop syndrome '76 is a viral disease that affects birds, notably chickens, ducks, geese and swans. It is characterised by a sudden drop in production of eggs as well as its eggshell quality in apparent healthy laying birds.
Avibirnavirus is a genus of viruses in family Birnaviridae. There is a single species in this genus: Infectious bursal disease virus, which infects chickens and other fowl. It causes severe inflammation of the bursa of Fabricius, and causes considerable morbidity and mortality.
