Genetic characterization of very virulent infectious bursal disease viruses from Latin America.

Very virulent infectious bursal disease viruses (vvIBDVs) were detected in phenol inactivated bursal samples obtained from Brazil, the Dominican Republic, and Venezuela. After nucleotide sequence analysis of the hypervariable region of VP2 gene, the vvIBDVs from Brazil and Venezuela exhibited all of the 14 nucleotide changes that are conserved in the European UK-661 and most other vvIBDV strains. However, the vvIBDV from the Dominican Republic presented 11 nucleotide changes that are conserved in vvIBDV strains. After phylogenetic analysis, the Latin American strains were found to be related to other vvIBDV strains from Europe, Asia, and Africa. However, Brazilian and Dominican vvIBDVs clustered in two separate subgroups, while the vvIBDVs from Venezuela were closely related to other strains from other parts of the world. By deduced amino acid sequence, the three conserved amino acid residues in vvIBDV strains (222 Ala, 256 Ile, and 294 Ile) were confirmed in the Latin American viruses, and one amino acid change (300 Ala) was unique to all vvIBDVs from the Dominican Republic. The occurrence of this change in the Dominican vvIBDVs may have an impact in their antigenic makeup. Results of this study indicate that the vvIBDVs detected in Latin America are genetically similar to IBDV strains from other parts of the world. However, vvIBDVs from Venezuela were more similar to the vvIBDV strains from Europe and Asia. Of all the samples analyzed, vvIBDVs from Brazil and the Dominican Republic exhibited more genetic changes. These changes may have emerged as a result of the different management practices and environmental conditions present in each particular geographic area.