Changes

==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''' <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.

 

==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.