Data concerning the taxonomy and properties of the members of the Circoviridae family have been presented. Representatives of the genus Circovirus and Gyrovirus have been discussed, including their role in causing diseases in several species of birds and in swine. Two viruses - porcine circovirus type 1 (PCV-1) and porcine circovirus type 2 (PCV-2) - have been isolated and characterized from swine. PCV-1 proved to be nonpathogenic or with minimal pathogenicity for swine. PCV-2 was pathogenic, causing postweaning multisystemic wasting syndrome (PMWS). The mechanism of pathogenicity was connected with causing immunosuppression by PCV-2, lymphoid tissue depletion and cytokine IL-10 over expression. These changes contributed to the appearance of clinical symptoms of PCV-2 subclinical infection triggering additional infections, caused by opportunistic microorganisms like Mycoplasma hyopneumoniae or porcine parvovirus. Non-infectious risk factors influencing the development of the clinical form of PMWS included mistakes in modern management practices contributing to lower resistance to infection and may also be a genetically determined susceptibility of race or line of swine. Since PMWS is a multifactorial syndrome indications for avoiding correspondent risk factors in management of swine production were mentioned. Vaccines containing PCV-2 antigens were evaluated as an important tool in controlling of PMWS. Available biologicals of this kind for pregnant sows and pigs during the production cycle were mentioned. Moreover, vaccination with vaccines against infections triggered by PCV-2 was recommended.
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