Extraneous chicken anemia virus (CAV)

Test code: S0265 - Ultrasensitive qualitative detection of extraneous chicken anemia virus by real time polymerase chain reaction

Extraneous chicken anemia virus (CAV) is a small, non-enveloped, icosahedral virus with a single-stranded, negative-sense, circular DNA genome (approximately 2.3 kb). It belongs to the genus Gyrovirus with the family Anelloviridae (previously classified under Circoviridae). The virus exclusively infects chickens and is not known to affect other bird species, though antibodies have been detected in Japanese (coturnix) quail.

Young chicks infected with this virus can develop severe disease symptoms including severe anemia, lethargy, depression, anorexia, pale appearance, weight loss, growth retardation, and poor feed conversion. This virus affects the hematolymphoid system, causing thymic and lymphoid atrophy that leads to immunosuppression. Hemorrhages (cutaneous, subcutaneous, and intramuscular) can occur, leading to "blue wing disease." The mortality rate of infected young chicks can range from 5% to 20% but can be up to 60% with co-infections or poor management. Infected older chickens usually have subclinical symptoms, but immunosuppression may develop in some cases, leading to increased susceptibility to secondary infections (bacterial, viral, or fungal) and reduction in vaccine efficacy. In some chickens with neutralizing antibodies to the virus, CAV can persist in gonads, potentially reactivating during sexual maturity due to an estrogen-responsive promoter in the viral genome (Brentano et al., 2005)..

This virus can transmit vertically from seronegative hens to their offspring. Horizontally, the virus is mainly transmitted through the fecal-oral route, via contaminated litter, feather dander, or inhalation. The virus is highly resistant to environmental conditions and disinfectants, making eradication challenging.

Infected chickens will develop antibodies 3–6 weeks post-infection. Thus, serology testing may not detect the viral infection at the acute phase. Molecular detection by polymerase chain reaction (PCR) is often used to confirm CAV in chicks with anemia (hematocrit <27%) or immunosuppression, often before antibodies are detectable (Sreekala et al., 2024).

Utilities:

• Help confirm the disease causing agent
• Environmental monitoring
• Help ensure that bird populations are free of extraneous chicken anemia virus
• Early prevention of spread of this virus among bird populations
• Minimize human exposure to this virus
• Safety monitoring of biological products and vaccines that derive from chickens

References:
Brentano, L., Lazzarin, S., Bassi, S.S., Klein, T.A., and Schat, K.A. (2005) Detection of chicken anemia virus in the gonads and in the progeny of broiler breeder hens with high neutralizing antibody titers. Vet. Microbiol. 105:65-72.

Sreekala, S.M., Kaur, G., and Dwivedi, P.N. (2024) Subclinical circulation of Chicken infectious anaemia virus- A Sero-molecular study. Braz. J. Microbiol. 2024 55:925-932.

Specimen requirements: 0.2 ml feces, or cloacal swab, or 0.2 ml whole blood in EDTA (purple top) tube, or 0.2 ml fresh or frozen tissue, or 0.2 ml cell culture, or environmental swab or swipe.

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time PCR

Normal range: Nondetected