Changes

==Epidemiology==

==Epidemiology==

Fomites may assist the transmission of the virus and the disease  can be '''spread both horizontally and vertically''', resulting in '''clinical and subclinical infections, respectively''' and the latter being of particular '''importance''' to '''intensive breeding populations'''.  

Fomites may assist the transmission of the virus and the disease  can be '''spread both horizontally and vertically''', resulting in '''clinical and subclinical infections, respectively''' and the latter being of particular '''importance''' to '''intensive breeding populations'''. '''Chicks hatching''' from infected layers of naive flocks '''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%.   

 

CAV isolates can be distinguished by using restriction endonuclease analysis of amplified DNA, but only a single serotype has so far been detected.  '''Chicks hatching''' from layers of naive flocks over a '''period of 3 to 6 weeks, show clinical signs after 10-14 days of age'''. After this period 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%.   

'''Horizontal transmission''' can occur in '''older chickens that lack maternal derived antibodies''' from '''faecal-oral route, fomites''' and as the '''virus is excreted''' by a small number of '''vertically infected hatch mates'''.

'''Horizontal transmission''' can occur in '''older chickens that lack maternal derived antibodies''' from '''faecal-oral route, fomites''' and as the '''virus is excreted''' by a small number of '''vertically infected hatch mates'''.

==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 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 develop that include;  immunoperoxidase staining, 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>.

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 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 develop that include;  immunoperoxidase staining, 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>.

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.

==Treatment==

==Treatment==