| Chicken anemiavirus | |
|---|---|
 | |
| A model of Chicken anemia virus | |
Virus classification | |
| (unranked): | Virus |
| Realm: | Monodnaviria |
| Kingdom: | Shotokuvirae |
| Phylum: | Commensaviricota |
| Class: | Cardeaviricetes |
| Order: | Sanitavirales |
| Family: | Anelloviridae |
| Genus: | Gyrovirus |
| Species: | Gyrovirus chickenanemia |
Chicken anemia virus (CAV), scientific nameGyrovirus chickenanemia, is a member of theAnelloviridae family which is found worldwide.[1] The virus only affectschickens.[2] CAV is a non-enveloped icosahedral single-stranded DNA virus,[3] which causes bone marrowatrophy,anemia, and severeimmunosuppression. Clinical signs of CAV infection are predominantly found in young chicks due tovertical transmission from the breeder hens whosematernal 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 followinghorizontal transmission of the virus via thefecal–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] When this virus was first discovered in 1979, it was namedchicken anemia agent.[1]
Clinical signs only occur in chicks less than three weeks of age.[4] During outbreaks of CAV, up to 10% of chicks can die.[5] Signs include a pale comb, wattle, eyelids, legs and carcass,anorexia, weakness, stunting, unthriftiness, weight loss,cyanosis,petechiation andecchymoses,lethargy, and sudden death. Neurological signs include dullness,depression andparesis.
In older chickens,an infection with no apparent symptoms may cause reduced growth rates due to a poorfeed conversion ratio.[2]
CAV infects precursorT cells in thethymus andhematopoietic stem cells in thebone marrow,[2] causing destruction of these cells viaapoptosis.[4]This reduces the production ofred blood cells (RBC) andwhite blood cells (WBC), leading to severeimmunosuppression andanemia.[2]
A presumptive diagnosis can be made based on the clinical signs and a lowhematocrit reading, e.g. below 27%. Virus isolation, increasedantibody titres,immunoperoxidase staining,ELISA,PCR or indirectimmunofluorescence can be used to confirm the presence of the virus.Post mortem findings show significantatrophy of thelymphoid organs, hemorrhage throughout the tissues, and pale watery bone marrow.
There is no specific treatment for infected birds.Culling of infected birds is normally performed in infected commercial flocks. Birds that have been infected developimmunity to the virus.
Vertical spread of the disease can be controlled by thevaccination of breeding hens with both live attenuated and wild vaccines. These vaccines reduce the vertical transmission rate. The vaccine has theATCvet codeQI01AD04 (WHO). Appropriate hygiene and biosecurity measures may be employed to control the disease.
2.Chicken Anaemia Virus Disease, expert reviewed and published by Wikivet, accessed 30/08/2011.