{{Short description|Species of virus}} {{virusbox | name = Chicken anemiavirus | image = File:Chicken_anemia_virus.jpg | image_alt = A model image of Chicken anemia virus | image_caption = A model of Chicken anemia virus | parent = Gyrovirus | species = Gyrovirus chickenanemia }} '''Chicken anemia virus''' ('''CAV'''), scientific name '''''Gyrovirus chickenanemia''''', is a member of the ''Anelloviridae'' family which is found worldwide.<ref name="Schat 2009" /> The virus only affects chickens.<ref name="Markey 2013"/> CAV is a non-enveloped icosahedral single-stranded DNA virus,<ref name="Fang 2017">{{cite journal|last1=Fang|first1=L|last2=Li|first2=Y|last3=Wang|first3=Y|last4=Fu|first4=J|last5=Cui|first5=S|last6=Li|first6=X|last7=Chang|first7=S|last8=Zhao|first8=P|title=Genetic Analysis of Two Chicken Infectious Anemia Virus Variants-Related ''Gyrovirus'' in Stray Mice and Dogs: The First Report in China, 2015.|journal=BioMed Research International|date=2017|volume=2017|article-number=6707868|doi=10.1155/2017/6707868|pmid=28326326|pmc=5343220|doi-access=free}}</ref> which causes bone marrow atrophy, anemia, and severe immunosuppression. Clinical signs of CAV infection are predominantly found in young chicks due to vertical transmission from the breeder hens whose maternal antibodies have not yet formed following exposure. Clinical disease is rare today because of the widespread practice of vaccinating breeders, but the subclinical form of the disease—which normally affects birds more than two weeks of age following horizontal transmission of the virus via the fecal–oral route—is ubiquitous. The virus is very resistant in the environment, making elimination very difficult.
The disease and virus have many names including chicken anemia, blue wing disease, anemia dermatitis syndrome, chicken/avian infectious anemia, hemorrhagic aplastic anemia syndrome, infectious chicken anemia, chicken infectious anemia virus, and chicken anemia agent.{{citation needed|date=June 2017}} When this virus was first discovered in 1979, it was named ''chicken anemia agent''.<ref name="Schat 2009">{{cite book|last1=Schat|first1=KA|chapter=Chicken Anemia Virus |series=Current Topics in Microbiology and Immunology |title=TT Viruses|date=2009|volume=331|pages=151–83|pmid=19230563|doi=10.1007/978-3-540-70972-5_10|isbn=978-3-540-70971-8}}</ref>
==Clinical signs== Clinical signs only occur in chicks less than three weeks of age.<ref name="Miller 2005" /> During outbreaks of CAV, up to 10% of chicks can die.<ref name="Quinn 2015">{{cite book|last1=Quinn|first1=PJ|last2=Markey|first2=BK|last3=Leonard|first3=FC|last4=Fitzpatrick|first4=ES|last5=Fanning|first5=S|title=Concise Review of Veterinary Microbiology|date=2015|publisher=John Wiley & Sons|isbn=9781118802687|page=146|edition=2nd|chapter=Chicken anaemia virus infection}}</ref> Signs include a pale comb, wattle, eyelids, legs and carcass, anorexia, weakness, stunting, unthriftiness, weight loss, cyanosis, petechiation and ecchymoses, lethargy, and sudden death. Neurological signs include dullness, depression and paresis.
In older chickens, an infection with no apparent symptoms may cause reduced growth rates due to a poor feed conversion ratio.<ref name="Markey 2013" />
==Pathogenesis== CAV infects precursor T cells in the thymus and hematopoietic stem cells in the bone marrow,<ref name="Markey 2013">{{cite book|last1=Markey|first1=B|last2=Leonard|first2=F|last3=Archambault|first3=M|last4=Cullinane|first4=A|last5=Maguire|first5=D|title=Clinical veterinary microbiology|date=2013|publisher=Elsevier Health Sciences|isbn=9780702055881|pages=547–550|edition=2nd|chapter=Chapter 46: Circoviridae}}</ref> causing destruction of these cells via apoptosis.<ref name="Miller 2005">{{cite journal|last1=Miller|first1=MM|last2=Jarosinski|first2=KW|last3=Schat|first3=KA|title=Positive and negative regulation of chicken anemia virus transcription|journal=Journal of Virology|date=March 2005|volume=79|issue=5|pages=2859–68|doi=10.1128/JVI.79.5.2859-2868.2005|pmid=15709005|pmc=548473}}</ref> This reduces the production of red blood cells (RBC) and white blood cells (WBC), leading to severe immunosuppression and anemia.<ref name="Markey 2013" />
==Diagnosis== A presumptive diagnosis can be made based on the clinical signs and a low hematocrit reading, e.g. below 27%. Virus isolation, increased antibody titres, immunoperoxidase staining, ELISA, PCR or indirect immunofluorescence can be used to confirm the presence of the virus. Post mortem findings show significant atrophy of the lymphoid organs, hemorrhage throughout the tissues, and pale watery bone marrow.
==Treatment and control== There is no specific treatment for infected birds. Culling of infected birds is normally performed in infected commercial flocks. Birds that have been infected develop immunity to the virus.
Vertical spread of the disease can be controlled by the vaccination of breeding hens with both live attenuated and wild vaccines. These vaccines reduce the vertical transmission rate. The vaccine has the ATCvet code {{ATCvet|I01|AD04}}. Appropriate hygiene and biosecurity measures may be employed to control the disease.
==References== {{Reflist|2}}
== External links == * https://web.archive.org/web/20131125042946/http://www.merckmanuals.com/vet/poultry/chicken_anemia_virus_infection/overview_of_chicken_anemia_virus_infection.html
2. [http://en.wikivet.net/Chicken_Anaemia_Virus_Disease Chicken Anaemia Virus Disease], expert reviewed and published by Wikivet, accessed 30/08/2011.
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Category:Animal viral diseases Category:Poultry diseases Category:Anelloviridae Category:Animal vaccines