Duck hepatitis is an acute and fatal disease in

duckling 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 ta ...

s caused by the Avihepatovirus DHV-1 and DHV-3. It causes

opisthotonus Opisthotonus or opisthotonos (from and ) is a state of severe hyperextension and spasticity in which an individual's head, neck and spinal column enter into a complete "bridging" or "arching" position. This extreme arched pose is an extrapyram ...

and

hepatitis Hepatitis is inflammation of the liver parenchyma, liver tissue. Some people or animals with hepatitis have no symptoms, whereas others develop yellow discoloration of the skin and whites of the eyes (jaundice), Anorexia (symptom), poor appetite ...

. DHV-1 is found worldwide. It causes disease in young ducklings, usually <6 weeks of age and spreads rapidly within a flock. It is the most

virulent Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most cases, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism—its abilit ...

of the DHV species. DHV-3 has only been reported in the USA.

Virus

DHV-1, is a

Picornavirus Picornaviruses are a group of related Viral envelope, nonenveloped RNA viruses which infect vertebrates including fish, mammals, and birds. They are viruses that represent a large family of small, Positive-sense single-stranded RNA virus, positi ...

that is distributed all over the world. It has significant impact on the poultry industry. It was first recorded in 1949 in

Long Island, New York Long Island is a densely populated continental island in southeastern New York (state), New York state, extending into the Atlantic Ocean. It constitutes a significant share of the New York metropolitan area in both population and land are ...

. In 2006 the pathogen's

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

was determined. This genome is composed of 7691

nucleotides Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...

and encodes and

polyprotein Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Protein degradation is a major regulatory mechanism of gene expression and contributes substantially to shaping mammalian proteomes. Uncatalysed, the hydrolysis o ...

of 2250

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...

. Duck hepatitis virus, DHV, type 1 (DHV-1), type 1a (DHV-1a), type 2 (DHV-2), and type 3 (DHV-3) are the four types of viruses that can cause disease in ducks. The pathology and pathogenicity between duck hepatitis virus type 1 and type 1a is, in essence, the same as one another. Duck Hepatitis is a Class B disease listed by the Office des International Epizooties. The virus cannot infect humans. ''Duck hepatitis virus'' type 1 is classified as an ''

enterovirus ''Enterovirus'' is a genus of positive-sense single-stranded RNA viruses associated with several human and mammalian diseases. Enteroviruses are named by their transmission-route through the intestine ('enteric' meaning intestinal). Serologic ...

'', DHV-2 is an ''

astrovirus 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 ani ...

'', and DHV-3 as a ''

picornavirus Picornaviruses are a group of related Viral envelope, nonenveloped RNA viruses which infect vertebrates including fish, mammals, and birds. They are viruses that represent a large family of small, Positive-sense single-stranded RNA virus, positi ...

''. DHV-1 has the most significant economic effect due to its high mortality rate when the spread is not controlled. The

virion A virion (plural, ''viria'' or ''virions'') is an inert virus particle capable of invading a Cell (biology), cell. Upon entering the cell, the virion disassembles and the genetic material from the virus takes control of the cell infrastructure, t ...

of DHV-1 is a 20-40 nm diameter, non-enveloped,

icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrical tha ...

particle. It is resistant to

ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

and

chloroform Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

. It possesses the ability to survive under normal environmental conditions for extended periods.

Clinical signs and diagnosis

Clinical signs include sudden death,

paresis In medicine, paresis (), compound word from Greek , (πᾰρᾰ- “beside” + ἵημι “let go, release”), is a condition typified by a weakness of voluntary movement, or by partial loss of voluntary movement or by impaired movement. Whe ...

paralysis Paralysis (: paralyses; also known as plegia) is a loss of Motor skill, motor function in one or more Skeletal muscle, muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory d ...

and

enophthalmos Enophthalmos is a posterior displacement of the eyeball within the orbit. It is due to either enlargement of the bony orbit and/or reduction of the orbital content, this in relation to each other. It should not be confused with its opposite, exo ...

. DHV-1 infection is most virulent, with death occurring within 1–2 hours of clinical signs. A preliminary diagnosis may be made based on the clinical signs and

post-mortem examination An autopsy (also referred to as post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of death; ...

Autopsy An autopsy (also referred to as post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of deat ...

should show an enlarged

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

, which appears greenish and displays distinct ecchymotic haemorrhages. Inoculation and direct

immunofluorescence Immunofluorescence (IF) is a light microscopy-based technique that allows detection and localization of a wide variety of target biomolecules within a cell or tissue at a quantitative level. The technique utilizes the binding specificity of anti ...

can be used to definitively diagnose DHV-1.

Treatment and control

No treatment is effective once infected. To prevent the disease,

vaccination Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating ...

( ATCvet code QI01) is commercially available against DHV-1 and immunization involves two or three inoculations. Additionally, DHV-1 can be prevented by strict isolation in the first 4–5 weeks of life. 5% phenol and

formaldehyde Formaldehyde ( , ) (systematic name methanal) is an organic compound with the chemical formula and structure , more precisely . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as ...

can be used to inactivate the viruses in the environment.

References

{{Taxonbar, from=Q5311496 Poultry diseases Animal viral diseases Enteroviruses Picornaviridae Animal vaccines

Virus

Clinical signs and diagnosis

Treatment and control

See also

References