Chicken infectious anemia (CIA)

Chicken infectious anemia virus (CIAV), a member of genus Gyrovirus of the family Circoviridae, is the causative agent of chicken infectious anaemia, an emerging infectious disease mainly of young chickens. It is the smallest avian virus (23-25 nm) with circular single stranded genome. In India, CIAV has been suspected since long on the basis of clinical symptoms and PM lesions. The virus is very hardy, highly contagious and can be transmitted both horizontally and vertically. Chicken is the only recognized natural host, but other domestic and wild birds have also been shown to be involved. Certain notable characteristics such as vertical transmission, detection in SPF eggs, and its highly contagious, hardy and ubiquitous nature have invited the attention of global poultry to CIAV.

The mortality in poultry is generally low but it is a potent immunosuppressive agent for very young unprotected chicks, thereby increasing their susceptibility to secondary viral, bacterial and fungal infections and depressing vaccinal immunity and production performance in the field situations.

Symptoms and lesions: Specific clinical disease is observed during the first 3-4 weeks of life. The disease is characterized by poor weight gain, severe anemia, aplasia of the bone marrow, lymphoid atrophy, subcutaneous and muscular hemorrhages and increased mortality. The virus seems to play a key role in the etiology of several multifactorial diseases, viz. hemorrhagic syndrome, hemorrhagic anemia syndrome, infectious/aplastic anemia, gangrenous dermatitis and blue wing diseases. Clinical disease is very much uncommon since most breeding stock seroconvert to CIAV either as a result of natural infection or vaccination before their laying, so that the progeny of infected breeder stocks are protected by maternal antibodies. Subclinical infections are common in chicks above 3 weeks of age. Vertical as well as horizontal mode of transmission is involved in the spread of CIAV among chickens resulting in clinical and sub-clinical infections, respectively.

Diagnosis: Affected flocks exhibiting pathognomic signs and lesions are relatively easy to identify. Tentatively CIAV infection can usually be diagnosed based on flock history, clinical picture, haematological and pathological findings in the affected birds. Confirmation of the disease needs isolation and identification of the virus. Laboratory diagnosis is based on virus isolation, antigen detection by PCR, and detection of specific antibodies by ELISA.

Prevention and control: Biosecurity in hatchery and in the commercial farms is the most important step. Introduction of disease-free chicks and avoiding any possible CIAV contamination is necessary for a known negative unit. In case of infected farms, destruction of all the birds with proper disposal should be done alongwith complete disinfection and dry period should be allowed before repopulation.