Introduction

A viral disease of chickens caused by Chicken Anaemia Virus or CAV. Prior to confirmation that it is in fact a virus it was known as Chicken Anaemia Agent or CAA.

Mortality is typically 5-10% but may be up to 60% if there are predisposing factors present such as intercurrent disease (Aspergillosis, Gumboro, Inclusion body heptatitis etc.) or poor management (e.g. poor litter quality).

Transmission is usually vertical during sero-conversion of a flock in lay, lateral transmission may result in poor productivity in broilers.

The virus is resistant to pH 2, ether, chloroform, heat (70°C for 1 hour, 80°C for 5 minutes) and many disinfectants even for 2 hours at 37°C. Hypochlorite appears most effective in vitro.

Signs

• Poor growth.
• Pale birds.
• Sudden rise in mortality (usually at 13-16 days of age).
• No clinical signs or effect on egg production or fertility in parent flock during sero-conversion.

Post-mortem lesions

• Pale bone marrow.
• PCV of 5-15% (normal 27-36%).
• Atrophy of thymus and bursa.
• Discoloured liver and kidney.
• Gangrenous dermatitis on feet, legs wings or neck.
• Acute mycotic pneumonia.

Diagnosis

Gross lesions, demonstration of ongoing sero-conversion in parent flock, virus may be isolated in lymphoblastoid cell line (MDCC-MSB1).

Treatment

Good hygiene and management, and control of other diseases as appropriate, may be beneficial. If gangrenous dermatitis is a problem then periodic medication may be required.

Prevention

Live vaccines are available for parents, their degree of attenuation is variable. They should be used at least 6 weeks prior to collecting eggs for incubation. Their use may be restricted to those flocks that have not sero-converted by, say, 15 weeks.

Immunity: there is a good response to field challenge (in birds over 4 weeks of age) and to attenuated live vaccines.

Serology: antibodies develop 3-6 weeks after infection, and may be detected by SN, Elisa, or IFA.