Novel Circoviruses from Birds Share Common Evolutionary Roots with Fish Origin Circoviruses

Circoviruses occur in a variety of animal species and are common pathogens of mammalian and avian hosts. In our study internal organ samples of wild birds were processed for screening of circoviral sequences. Two novel viruses were identified and characterized in specimens of a little bittern and a European bee-eater that suffered from wing injuries, were weakened, had liver or kidney failures, and finally succumbed at a rescue station. The 1935 nt and 1960 nt long viral DNA genomes exhibited a genomic structure typical for circoviruses and were predicted to encode replication-associated protein in the viral strand, and a capsid protein in the complementary strand of the replicative intermediate DNA form. The genome of the newly described viruses showed 37.6% pairwise identity with each other and ≤41.5% identity with circovirus sequences, and shared a common branch with fish, human and Weddel seal circoviruses in the phylogenetic tree, implying evolutionary relationship among the ancestors of these viruses. Based on the results the little bittern and European bee-eater circoviruses represent two distinct species of the Circovirus genus, Circoviridae family.