''Chicken anemia virus'', or CAV, is currently a member of the '' Anelloviridae'' family which is found worldwide. The virus only affects chickens. CAV is a non-enveloped icosahedral single stranded DNA virus, which causes bone marrow

atrophy Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations (which can destroy the gene to build up the organ), poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply t ...

, anemia, and severe immunosuppression. Clinical signs of CAV infection are predominantly found in young chicks due to

vertical transmission Vertical transmission of symbionts is the transfer of a microbial symbiont from the parent directly to the offspring. Many metazoan species carry symbiotic bacteria which play a mutualistic, commensal, or parasitic role. A symbiont is acquire ...

from the breeder hens whose

maternal antibodies Passive immunity is the transfer of active humoral immunity of ready-made antibodies. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when h ...

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 The fecal–oral route (also called the oral–fecal route or orofecal route) describes a particular route of transmission of a disease wherein pathogens in fecal particles pass from one person to the mouth of another person. Main causes of fecal ...

—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. When this virus was first discovered in 1979, it was named ''chicken anemia agent''.

Clinical signs

Clinical signs only occur in chicks less than three weeks of age. During outbreaks of CAV, up to 10% of chicks can die. Signs include a pale comb, wattle, eyelids, legs and carcass, anorexia, weakness, stunting, unthriftiness, weight loss,

cyanosis Cyanosis is the change of body tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the red blood cells of the capillary bed. Body tissues that show cyanosis are usually in locations ...

petechia A petechia () is a small red or purple spot (≤4 mm in diameter) that can appear on the skin, conjunctiva, retina, and Mucous membrane, mucous membranes which is caused by haemorrhage of capillaries. The word is derived from Italian , 'freckle,' ...

tion 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 In animal husbandry, feed conversion ratio (FCR) or feed conversion rate is a ratio or rate measuring of the efficiency with which the bodies of livestock convert animal feed into the desired output. For dairy cows, for example, the output is mi ...

Pathogenesis

CAV infects precursor T cells in the thymus and

hematopoietic stem cell Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the very first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within t ...

s in the

bone marrow Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It is composed of hematopoietic ce ...

, causing destruction of these cells via

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...

. This reduces the production of

red blood cells Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek language, Greek ''erythros'' for "red" and ''k ...

(RBC) and white blood cells (WBC), leading to severe immunosuppression and anemia.

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 Immunoperoxidase is a type of immunostain used in molecular biology, medical research, and clinical diagnostics. In particular, immunoperoxidase reactions refer to a sub-class of immunohistochemical or immunocytochemical procedures in which the ant ...

staining, ELISA,

PCR PCR or pcr may refer to: Science * Phosphocreatine, a phosphorylated creatine molecule * Principal component regression, a statistical technique Medicine * Polymerase chain reaction ** COVID-19 testing, often performed using the polymerase chain r ...

or indirect

immunofluorescence Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on microbiological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specif ...

can be used to confirm the presence of the virus. Post mortem findings show significant

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 Immunity may refer to: Medicine * Immunity (medical), resistance of an organism to infection or disease * ''Immunity'' (journal), a scientific journal published by Cell Press Biology * Immune system Engineering * Radiofrequence immunity desc ...

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 . Appropriate hygiene and biosecurity measures may be employed to control the disease.

References

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
Chicken Anaemia Virus Disease
expert reviewed and published by Wikivet, accessed 30/08/2011. {{Taxonbar, from=Q5096284 Animal viral diseases Poultry diseases Circoviridae Animal vaccines