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Types of disease

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There are four main types of disease affecting poultry: metabolic and nutritional diseases; infectious diseases; parasitic diseases; and behavioural diseases.

Metabolic and nutritional diseases

These are conditions caused by a disturbance of normal metabolic functions either through a genetic defect, inadequate or inappropriate nutrition or impaired nutrient utilisation. These include Fatty Liver Syndrome, Perosis (or slipped tendon), Rickets and Cage Layer Fatigue.

Infectious diseases

An infectious disease is any disease caused by invasion of a host by a pathogen which subsequently grows and multiplies in the body. Infectious diseases are often contagious, which means they can be spread directly or indirectly from one living thing to another. These include Avian Encephalomyelitis, Avian Influenza, Avian Tuberculosis, Chicken Anaemia Virus Infection (or CAV), Chlamydiosis, Egg Drop Syndrome (or EDS), Fowl Cholera (or Pasteurellosis), Fowl Pox, Infectious Bronchitis, Infectious Bursal Disease (or Gumboro), Infectious Coryza, Infectious Laryngotracheitis, Lymphoid Leukosis, Marek’s Disease, Mycoplasmosis, Necrotic Enteritis, Newcastle Disease and Salmonellosis.

Parasitic diseases

Parasitic diseases are infections or infestations with parasitic organisms. They are often contracted through contact with an intermediate vector, but may occur as the result of direct exposure. A parasite is an organism that lives in or on, and takes its nourishment from, another organism. A parasite cannot live independently. These include Coccidiosis, Cryptosporidiosis, Histomoniasis, Lice and Mites, Parasitic Worms (or Helminths), Toxoplasmosis and Trichomoniasis.

Behavioural diseases

Abnormal behavioural patterns can lead to injury or ill health of the abnormally behaving bird and/or its companions. These include Cannibalism (or aggressive pecking).

List of avian diseases

Poultry can be affected by many types of disease, and a wide variety of pests (and behavioural problems) including those in the list below. Diseases caused by Viruses Avian Influenza Avian Encephalomyelitis Big... read more


Under construction Ascites is considered a metabolic disorder and is common in commercially grown chicken and ducks. It is thought that in fast growing breeds, organs are unable to supply the... read more

Avian encephalomyelitis

Avian encephalomyelitis (AE) is a viral infection of the central nervous system of poultry, primarily chickens, turkeys, Japanese (coturnix) quail, and pheasants. It is found worldwide and is characterised by ataxia (loss of muscle coordination)... read more

Avian influenza

Avian influenza (AI) is a highly contagious viral infection which may cause up to 100% mortality in domestic chickens or turkeys. The disease is caused by a virus that belongs to the family... read more

Avian Intestinal Spirochaetosis

Avian Intestinal Spirochaetosis (AIS) is a disease that affects commercial laying and meat breeding hens and results from the colonisation of the caeca and rectum by one or more species of... read more

Avian tuberculosis

Avian tuberculosis is chronic bacterial infection that spreads slowly through a flock. All bird species appear to be susceptible, however pheasants seem highly susceptible whereas turkeys rarely succumb to the disease.... read more

Cannibalism (or aggressive pecking)

Pecking is the natural means by which poultry investigate their surroundings and establish a stable social order, however this behaviour can escalate to the stage where birds will literally peck... read more

Chicken anaemia virus infection (or CAV)

Chicken anaemia virus infection (known generally in the industry as CAV) is an acute viral infection of chickens that is found worldwide. The disease is not known to affect any other bird species,... read more


Chlamydophilosis is a bacterial infection that can range from subclinical through to acute or chronic disease states. It is characterised by respiratory, digestive or systemic infection. Chlamydophilosis can affect a wide variety of... read more


Coccidiosis is one of the most common and economically important diseases of chickens worldwide. It is caused by a parasitic organism that damages the host’s intestinal system, causing loss of production, morbidity and... read more


Colibacillosis is an infectious disease caused by the bacterium Escherichia coli (also known simply as E. coli), and is seen in poultry flocks worldwide. E. coli can cause an infection under the skin, known as cellulitis, and is... read more


Cryptosporidiosis is a parasitic disease that affects quail, pheasants, peafowl, waterfowl, chickens, turkeys, finches and psittacines (such as parrots). Cryptosporidia are poorly host-specific and can affect other animal species including humans, other mammals,... read more

Candidiasis (or crop mycosis)

Under construction Candidiasis (or crop mycosis) is…

Egg drop syndrome (or EDS)

Egg drop syndrome (EDS) is caused by a viral infection in laying hens. It is characterised by production of soft-shelled and shell-less eggs in apparently healthy birds, and leads to a sudden drop... read more

Fatty liver syndrome

Fatty liver syndrome is a condition that affects only hens, primarily caged layers. It is a metabolic or nutritional disease and is characterised by general obesity with an enlarged, fatty liver that becomes... read more

Fowl cholera (or pasteurellosis)

Fowl cholera is a contagious bacterial infection. The disease can range from acute septicaemia (blood poisoning) to chronic and localised infections. Domestic fowl, game birds and small feral birds are susceptible. Turkeys... read more

Fowl pox

Fowl pox is a relatively slow-spreading viral infection that affects most bird species, including all commercial forms of poultry. It occurs in both a wet and dry form. The wet form is characterised... read more


Histomoniasis is a parasitic protozoan infection of turkeys, chickens, peafowl and several game bird species. Most infections are fatal in turkeys, but mortality is less common in other birds. Although chickens are relatively... read more

Inclusion body hepatitis (or Fowl adenovirus type 8)

Under construction Inclusion body hepatitis or Fowl adenovirus type 8) is…..

Infectious bronchitis

Infectious bronchitis is a highly contagious viral respiratory infection of chickens, however the virus will also infect the urogenital and gastrointestinal tracts. The clinical signs of infectious bronchitis are non-specific and so laboratory... read more

Infectious bursal disease (or Gumboro)

Infectious bursal disease (IBD), also known as Gumboro, is a highly contagious viral infection that is found in chicken flocks in most countries. The severity of the disease will depend on the... read more

Infectious coryza

Infectious coryza is a contagious bacterial respiratory infection of chickens. While there are reports of a similar disease in other birds such as pheasants and guinea fowl, there is considerable doubt if these... read more

Infectious laryngotracheitis

Infectious laryngotracheitis (ILT) is a highly contagious viral respiratory infection of chickens and pheasants and the disease is notifiable in most Australian states. A number of other bird species such as turkeys, ducks,... read more

Leg and skeletal problems

Leg and skeletal problems are a very important area especially from welfare points of view and are common in some breeds of broilers. Issues include rickets, TD, spondylolisthesis, slipped tendons, tibial rotation and... read more

Lice and mites

Lice and mites are common external parasites of poultry. Lice are insects, while mites belong to the same family as spiders. There are a large number of lice and mite species that can... read more

Lymphoid leukosis

Lymphoid leukosis is a neoplastic (tumour causing) viral infection of chickens that is found in flocks worldwide. The virus has been eradicated from some SPF (specific pathogen free) flocks. Globally, the frequency of... read more

Lympoid Tumour Disease (Reticuloendotheliosis)

Reticuloendotheliosis or Lympoid Tumour Disease is a retrovirus infection that is common in chickens, turkeys, ducks, geese and quail with morbidity rates up to 25%. A gradual increase in mortality and... read more

Marek’s disease

Marek’s disease virus (MDV) is a highly contagious viral infection that predominantly affects chickens but can also affect pheasants, quail, gamefowl and turkeys. It is one of the most common diseases that affects... read more


Mycoplasmosis is a collective term for infectious diseases caused by the micro-organisms called mycoplasmas. There are a number of mycoplasmas that can infect poultry, with Mycoplasma gallisepticum (MG) (which affects a number of bird... read more

Necrotic enteritis

Necrotic enteritis (NE) is the most common and financially devastating bacterial disease in modern broiler flocks. Early signs of an NE outbreak are often wet litter and diarrhoea, and an increase in... read more

Newcastle disease

Newcastle disease is a highly contagious viral infection that affects many species of domestic and wild birds to varying degrees. Domestic fowl, turkeys, pigeons and parrots are most susceptible while a mild form... read more

Parasitic worms (or Helminths)

All birds are naturally subject to infection by parasitic worms, or Helminths. The majority of Helminths infect the digestive tract but some are also found in other organs, such as the brain, trachea and eye. Not all Helminth... read more

Rickets and cage layer fatigue

Rickets and cage layer fatigue are nutritional diseases of chickens, turkeys and ducks that results in soft bones. Often the leg bones become bowed and hamper the bird’s ability to stand and walk. The... read more


Toxoplasmosis is a zoonotic (can be transmitted from animals to humans) parasitic protozoan disease and is rare in poultry. It is more common in aviaries and backyard poultry than commercial producers. It is... read more


Trichomoniasis is a parasitic protozoan disease that affects domestic fowl, pigeons, doves, and hawks. It occurs in the digestive as either the ‘lower’ form, which is characterised by depression, weight loss and watery yellow... read more

Viral arthritis (tenosynovitis)

Viral arthritis also known as tenosynovitis is caused by reoviruses, and the clinical signs and manifestation of disease varies markedly depending on the pathogenicity and tropism (preferred tissue to infect) of... read more

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