Animal Diseases –
Avian / Poultry

Avian influenza

Epidemiology
AI, also known as “bird flu,” is a highly contagious viral disease that can infect several species of domesticated birds (chickens, turkeys, quails, guinea fowls, etc.) and wild birds (ducks). It is caused by an A-type influenza virus: a single-stranded RNA virus belonging to the Orthomyxoviidae family. This virus has also been isolated in different mammals, including humans and pigs (the source of genetic recombinations between avian and human viruses).

Signs
Avian influenza can present many signs in birds, from minor disease (with little or no clinical signs) to disease that can quickly become fatal and lead to a serious epidemic. Highly pathogenic avian influenza (A virus belonging to H5, H7, and H9 subtypes) is characterized by serious signs and a fast deterioration towards death. The death rate can then reach 100% in less than 2 days. Strains that are highly pathogenic can lead to serious respiratory disease on humans.

Transmission
Virus transmission between birds occurs mainly by direct contact (respiratory secretion and fecal material), but can also be indirect (by food or contaminated water, bird droppings carrying the virus, and contaminated materials). Several species of bird are more resistant to the infection than others, such as ducks, which can be infected by pathogenic strains that present unnoticeable clinical signs. The highly pathogenic A/H5N1 strain shows clinical signs in domesticated poultry (chickens and turkeys) and in certain wild birds. The infections caused by highly pathogenic virus strains are rare and must not be confused with the infections caused by less pathogenic strains, which can also belong to the H5, H7, and H9 subtypes.

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Infectious bronchitis (IB)Top

Epidemiology
The infectious bronchitis virus (IBV) is a single-stranded RNA virus belonging to the Coronavirus genus. It can cause contagious respiratory disease, common for all types of poultry, and can become a complex respiratory disease with a significant mortality rate. IB is present all over the world in different clinical forms: the main one is a classical respiratory syndrome.

Many IBV variants
Infections caused by IBV can also lead to nephritis (acute or chronic) or to disorders within the hen clutch. There are many IBV variants and most ELISA kits show cross-reactions to those different variants.

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Newcastle disease (ND)Top

Epidemiology
Newcastle disease is an acute, virulent, and very contagious disease that mainly affects domesticated or wild birds, but also humans. This disease is caused by a Paramyxovirus of type 1, wrapped, with single-stranded RNA, and whose strains have variable virulence.

Signs
ND is a worldwide issue that is mainly characterized by a respiratory disease, but depression, nervous signs, or diarrhea can be dominant clinical signs.

Transmission
The virus is spread by droppings, expectoration, and oral secretions. The contamination can be by direct or indirect (insects, wild birds, humans, materials) contact. Newcastle disease is a major health issue in poultry breeding as it has a mortality rate of close to 100% for nonvaccinated animals, and the infection spreads very fast.

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Infectious bursal disease (IBD) or Gumboro diseaseTop

Epidemiology
IBD is a contagious viral disease that was described for the first time in 1962 in the city of Gumboro, DE (in the US)—hence its alternative name. It affects domesticated and wild birds in all the regions of the world, and its economic impact is significant.

IBD is caused by a very resistant virus, not wrapped, in two double-stranded RNA segments, which belongs to the Birnaviridae family and the Avibirnavirus genus. The virus is passed on horizontally, directly and indirectly, and the incubation time is short (between 2 and 3 days).

While turkeys, geese, and wild birds are infected and are vectors of the disease, only the young chickens (mainly between 3 and 6 weeks) develop the disease, which is often fatal. There is also an immunodepressive type of IBD caused by a premature infection of chicks less than 15 days old that can lead to significant economic losses.

Signs
The signs are diarrhea, dehydration, and damage to the bursa of Fabricus (immature lymphocytes B, affected by the virus). The acute form of the disease is caused by a hypervirulent strain and its diagnosis is more difficult. Birds are prostrated, sensitive to cold, anorexic, and suffer from diarrhea.

Breeders rely on vaccination to prevent virus replication
To prevent the premature replication of the virus, the presence of neutralizing maternal antibodies is essential for chicks, and vaccinal prevention is necessary and generalized, in particular for breeders.

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Avian mycoplasmosisTop

Epidemiology and signs
Avian Mycoplasma are responsible for many diseases in poultry, especially chronic respiratory diseases. The characteristic signs of the disease are respiratory rales, coughing, nasal discharge in chickens, and sinusitis in turkeys. The development of clinical manifestations, such as reduced growth and egg production, is usually slow to develop. Two mycoplasma species are primarily involved in poultry diseases: M. synoviae and M. gallisepticum.

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Avian MetapneumovirusTop

Epidemiology
Numerous strains of avian pneumoviruses (APVs) have been isolated from different species of intensively bred birds (chickens, hens, guinea fowls, and ducks). They can cause respiratory disease and/or clutch drops. Avian metapneumoviruses are associated with two diseases with similar symptoms and lesions: infectious rhinotracheitis in turkeys (IRT), and the swollen head syndrome (SHS) in poultry and guinea fowl.

Metapneumoviruses are single-stranded RNA viruses belonging to the Paramyxoviridae family. The antigenic and molecular characterization of these viruses has identified four subcategories: A, B, C, and D. Subcategories A (English), B (French), and D correspond to viruses isolated from turkeys in Europe, with the B subcategory being widely dominant in Europe. The C subcategory corresponds to a strain of pneumovirus isolated in the USA, with antigenic and biological characteristics slightly different from those of the other typical subtypes.

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