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Also known as: '''''Chicken Anaemia — Blue Wing Disease — BWD — Anemia Dermatitis Syndrome — Chicken/Avian Infectious Anaemia — Hemorrhagic Aplastic Anemia Syndrome — Infectious Chicken Anaemia — CAV — Chicken Infectious Anaemia Virus — CIAV — Chicken Anaemia Agent — CAA'''''

Also known as: '''''Chicken Anaemia — Blue Wing Disease — BWD — Anemia Dermatitis Syndrome — Chicken/Avian Infectious Anaemia — Hemorrhagic Aplastic Anemia Syndrome — Infectious Chicken Anaemia — CAV — Chicken Infectious Anaemia Virus — CIAV — Chicken Anaemia Agent — CAA'''''

{{Taxobox

{{Taxobox

Chicken anaemia virus disease is commonly referred to as chicken anaemia, chicken infectious anaemia and blue wing disease.  It is caused by the '''''chicken anaemia virus''''' (CAV), which is a non-enveloped icosahedral '''single stranded DNA (ssDNA) virus'''.  CAV  is 23-25 nm diameter and is part of the [[:Category:Circoviridae|Circoviridae]], composing of a small circular genome of negative sense. The virus is '''difficult to eradicate''' as it is '''very hardy and resistant to high temperatures, acidic pH (pH3), chloroform''' and '''commercial disinfectants'''.  CAV can be '''destroyed with hypochlorite and iodophor''' and '''formalin can reduce its infectivity'''.  It  is also morphologically and antigenically different to other circoviruses such as [[Porcine Circoviruses|''Porcine circovirus'' (PCV)]] and [[Psittacine Beak and Feather Disease| ''Psittacine beak and feather disease virus'' (PBFDV)]].   

Chicken anaemia virus disease is commonly referred to as chicken anaemia, chicken infectious anaemia and blue wing disease.  It is caused by the '''''chicken anaemia virus''''' (CAV), which is a non-enveloped icosahedral '''single stranded DNA (ssDNA) virus'''.  CAV  is 23-25 nm diameter and is part of the [[:Category:Circoviridae|Circoviridae]], composing of a small circular genome of negative sense. The virus is '''difficult to eradicate''' as it is '''very hardy and resistant to high temperatures, acidic pH (pH3), chloroform''' and '''commercial disinfectants'''.  CAV can be '''destroyed with hypochlorite and iodophor''' and '''formalin can reduce its infectivity'''.  It  is also morphologically and antigenically different to other circoviruses such as [[Porcine Circoviruses|''Porcine circovirus'' (PCV)]] and [[Psittacine Beak and Feather Disease| ''Psittacine beak and feather disease virus'' (PBFDV)]].   

CAV produces '''three types of proteins''' of '''VP1''' (52kDA), '''VP2''' (24 kDA) and '''VP3''' (14 kDA) kDa. '''Structural protein VP1''' is the intracellular form of the capsid protein and '''VP2''' is found in small amounts in the '''purified virus'''. Vaccines need to contain both of these to be antigenic. '''VP3''' is involved in '''apoptosis''' which involves the '''programmed and controlled death of a cell'''.  This process does not involve the lysis of the cell and therefore limits damage to surrounding cells and tissues. It also initiates pathogenicity and '''apoptosis of infected stem cells in the bone marrow (BM)''', resulting in damage to the BM.  As a result, the virus '''inhibits the production of red blood cells (RBC), white blood cells (WBC) and platelets.  Lymphoid tissues are also affected'''. Due to its apoptotic properties VP3 has the potential to be an anti-cancer agent. It is '''not considered a zoonosis'''.

CAV produces '''three types of proteins''': '''VP1''' (52kDA), '''VP2''' (24 kDA) and '''VP3''' (14 kDA). '''Structural protein VP1''' is the intracellular form of the capsid protein and '''VP2''' is found in small amounts in the '''purified virus'''. Vaccines need to contain both of these to be antigenic. '''VP3''' is involved in '''apoptosis''' which involves the '''programmed and controlled death of a cell'''.  This process does not involve the lysis of the cell and therefore limits damage to surrounding cells and tissues. It also initiates pathogenicity and '''apoptosis of infected stem cells in the bone marrow (BM)''', resulting in damage to the BM.  As a result, the virus '''inhibits the production of red blood cells (RBC), white blood cells (WBC) and platelets.  Lymphoid tissues are also affected'''. Due to its apoptotic properties VP3 has the potential to be an anti-cancer agent. It is '''not considered a zoonosis'''.

CAV is difficult to grow but can be grown in chickens, embryonated eggs and in cell culture. The most commonly used cell line is MDCC-MSB1 (a Marek’s disease transformed chicken lymphocyte cell line) <ref name=" Yuasa, 1983">Yuasa, N. (1983) '''Propagation and infectivity titration of the Gifu-1 strain of chicken anemia agent in a cell line (MDCC-MSB1) derived from Marek's disease lymphoma'''. ''National Institute of Animal Health Quarterly'', Japan, 23(1):13-20; 18 ref. </ref> <ref name=" Goryo et al., 1987"> Goryo, M., Suwa, T., Matsumoto, S., Umemura, T., Itakura, C. (1987) '''Serial propagation and purification of chicken anaemia agent in MDCC-MSB1 cell line'''. ''Avian Pathology'', 16(1):149-163; [7 fig.]; 18 ref. </ref>. Virus production in this way may lead to the potential for Marek’s disease virus contamination of vaccines.

CAV is difficult to grow but can be grown in chickens, embryonated eggs and in cell culture. The most commonly used cell line is MDCC-MSB1 (a Marek’s disease transformed chicken lymphocyte cell line). Virus production in this way may lead to the potential for Marek’s disease virus contamination of vaccines.

==Signalment==

==Signalment==

==Epidemiology==

==Epidemiology==

The disease is mainly spread by '''vertical transmission''', which is of particular importance to intensive breeding populations. The '''age''' of the bird has a marked effect on the '''development of clinical signs'''.'''Chicks hatching''' from infected layers of naive flocks (vertical transmission) '''show clinical signs after 10-14 days of age''' over a '''period of 3 to 6 weeks'''. After which the breeder layers develop sufficient CAV antibodies to stop the transmission of the virus to the egg. '''Mortality peaks''' during the '''third week of life''' around 5 to 10% but can be as high as 60%. Whereas in '''older chicks''' (>14 days old) that become infected via faecal-oral route (horizontal transmission) '''do not exhibit clinical signs''' but the '''growth and health of the birds may be affected''' <ref name="McNulty et al., 1991">McNulty, M.S., McIlroy, S.G., Bruce, D.W., Todd, D., (1991) '''Economic effects of subclinical chicken anaemia agent infection in broiler chickens.''' ''Avian Diseases,'' 35:263-268. </ref>. Fomites may assist the transmission of the virus.

The disease is mainly spread by '''vertical transmission''', which is of particular importance to intensive breeding populations. The '''age''' of the bird has a marked effect on the '''development of clinical signs'''.'''Chicks hatching''' from infected layers of naive flocks (vertical transmission) '''show clinical signs after 10-14 days of age''' over a '''period of 3 to 6 weeks'''. After which the breeder layers develop sufficient CAV antibodies to stop the transmission of the virus to the egg. '''Mortality peaks''' during the '''third week of life''' around 5 to 10% but can be as high as 60%. '''Older chicks''' (>14 days old) that become infected via faecal-oral route (horizontal transmission) '''do not exhibit clinical signs''' but the '''growth and health of the birds may be affected'''. Fomites may assist the transmission of the virus.

==Distribution==

==Distribution==

'''Worldwide'''  distribution including commercial poultry and in specific pathogen free (SPF) flocks.

'''Worldwide'''  distribution including commercial poultry and in specific pathogen free (SPF) flocks.

Diagnosis can be made on the above clinical signs and '''decreases in haematocrit''' from normal ranges (32-37.5%) to '''below 27%''' and increases in the amount of [[Haematopoiesis - Overview|immature blood cells]].  

Diagnosis can be made on the above clinical signs and '''decreases in haematocrit''' from normal ranges (32-37.5%) to '''below 27%''' and increases in the amount of [[Haematopoiesis - Overview|immature blood cells]].  

''' Virus isolation''' can confirm diagnosis of disease but growth of CAV in cell cultures can be difficult. Levels of infection can be estimated by the detection of raising antibody titres and many diagnostic tests have been developed that include  immunoperoxidase staining, [[ELISA testing|ELISA]]<ref name=" Todd et al., 1999">Todd, D., Mawhinney, K.A., Graham, D.A., Scott, A.N.J.,(1999) '''Development of a blocking enzyme-linked immunosorbent assay for the serological diagnosis of chicken anaemia virus'''. ''Journal of Virological Methods'', 82(2):177-184; 17 ref. </ref>, PCR, dot blot hybridisation and indirect [[immunofluorescence]]<ref name=" Sun et al., 1999">Sun, W., Wu, Z.Q., Hu, Q.H., Li,  S.X., Li, G., (1999) ''' Preliminary research on the diagnosis of chicken infectious anaemia by PCR, dot-blot-hybridization assay and indirect immunofluorescence assay'''. '''Journal of Nanjing Agricultural University'', 22(3):69-72. </ref>.

''' Virus isolation''' can confirm diagnosis of disease but growth of CAV in cell cultures can be difficult. Levels of infection can be estimated by the detection of raising antibody titres and many diagnostic tests have been developed that include  immunoperoxidase staining, [[ELISA testing|ELISA]], PCR and indirect [[immunofluorescence]].

Post mortem finding include severe atrophy of the lymphoid organs. The thymus, bursa of Fabricius, and to a lesser extent the spleen are all affected by a depletion of lymphocytes and sequential hyperplasia of reticular cells. Common finding include haemorrhages throughout the skeletal muscle and subcutaneous tissue and pale watery bone marrow. Severe aplasia of the bone marrow occurs and haematopoietic cells are replaced with adipose tissue, giving the bone marrow its watery texture and characteristic change in colour from red to yellow.

Post mortem finding include severe atrophy of the lymphoid organs. The thymus, bursa of Fabricius, and to a lesser extent the spleen are all affected by a depletion of lymphocytes and sequential hyperplasia of reticular cells. Common finding include haemorrhages throughout the skeletal muscle and subcutaneous tissue and pale watery bone marrow. Severe aplasia of the bone marrow occurs and haematopoietic cells are replaced with adipose tissue, giving the bone marrow its watery texture and characteristic change in colour from red to yellow.

==References==

==References==

[[Category:Circoviridae]]

[[Category:Circoviridae]]

[[Category:Avian Viruses]]

[[Category:Avian Viruses]]

[[Category:Lymphoreticular and Haematopoietic Diseases - Birds]]

[[Category:Lymphoreticular and Haematopoietic Diseases - Birds]]

[[Category:To Do - CABI review]]

[[Category:CABI Expert Review Completed]][[Category:CABI AHPC Pages]]