Search

The establishment of viral pathogens in new host environments following spillover events probably requires adaptive changes within both the new host and pathogen. After many generations, signals for ancient cross-species transmission may become lost and a strictly host-adapted phylogeny may mimic true co-divergence while the virus may retain an inherent ability to jump host species. The mechanistic basis for such processes remains poorly understood. To study the dynamics of virus–host co-divergence and the arbitrary chances of spillover in various reservoir hosts with equal ecological opportunity, we examined structural constraints of capsid protein in extant populations of Beak and feather disease virus (BFDV) during known spillover events. By assessing reservoir-based genotype stratification, we identified co-divergence defying signatures in the evolution BFDV which highlighted primordial processes of cryptic host adaptation and competing forces of host co-divergence and cross-species transmission. We demonstrate that, despite extensive surface plasticity gathered over a longer span of evolution, structural constraints of the capsid protein allow opportunistic host switching in host-adapted populations. This study provides new insights into how small populations of endangered psittacine species may face multidirectional forces of infection from reservoirs with apparently co-diverging genotypes. [ABSTRACT FROM AUTHOR]

Beak and feather disease virus (BFDV) is a causative agent for psittacine beak and feather disease (PBFD), which shows a characteristic feather disorder in psittacine birds. Nineteen budgerigars, which were clinically suspected to have PBFD, were examined by two polymerase chain reactions (PCR), which target each of open reading frames (ORFs) V1 and C1. All of the 19 samples were detected BFDV by the PCR targeting ORF C1, whereas only two of them were detected by the PCR targeting ORF V1. It was assumed that BFDV derived from budgerigar (budgerigar BFDV) has two genotypes, which are tentatively classified as budgerigar BFDV genotype 1 and genotype 2 by the PCR amplification patterns. Whole genome sequences of six budgerigar BFDVs were determined to reveal the existence of two genotypes. In the phylogenic analysis, six budgerigar BFDV sequences formed a unique group branched from the other 23 published BFDV sequences. The budgerigar BFDV genotype 1 and genotype 2 were also segregated each other, and budgerigar BFDV genotype 2 was particularly distantly related with the other BFDVs. These results suggest budgerigar BFDV is a unique in the known BFDVs and is divided into two genotypes. [ABSTRACT FROM AUTHOR]