Chicken anemia caused by circoviruses has been a vital economical and sanitary problem in poultry breeding in recent years. The aim of the investigation was to establish the prevalence of CAV in breeding flocks of meat poultry and slaughter chickens. The examinations were done on 25 reproductive farms of meat poultry (from 12 days to 60 weeks old) and on 39 farms of slaughter chickens aged from 3 days to 9 weeks. The prevalence of specific CA antibodies in sera was detected by the use of ELISA (Guildhay, England). The results have been interpreted on the basis of the estimated value of the coefficient S/P ELISA. Antibodies against CAV were found in sera of poultry from 23 (92%) reproductive flocks. Seroconversion was found in 4 (66.7%) out of 6 floks of poultry aged up to 20 weeks, and in 100% of the flocks at production period (21-60 weeks of age). Seroconversion was present in slaughter chickens from 24 farms (61.5%). Generally, the percentage of positive results, was higher in reproductive flocks (mean value for the age groups of 87.2% and 84.5%) in comparison to slaugher chickens (56.7% and 58.3%, respectively). Moreover, the intensity of serological responses to CAV infection represented by S/P ELISA was higher for poultry (from 0.26 to 1.85) than in slaughter chickens (from 0.25 to 1.25). The poultry breeding flocks were free of clinical symptoms of CA before serological examinations. However, in all slaughter chicken flocks CAV serologically positive symptoms of CA (anemia, atrophy of lymphatic organs, and flock differentation) were present from the 10-14 days. Losses in the majority of slaughter chicken flocks ranged from 1.75% at the 1st week of age up to a total 13% at the 6th week of breeding.
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