Molecular characterization of infectious bursal disease virus from commercial poultry in the United States and Latin America.

From June 1999 to September 2001, 216 bursal samples from broiler farms in the United States and from countries of Latin America were submitted to the Poultry Diagnostic and Research Center at the University of Georgia for the purpose of genotyping field infectious bursal disease viruses (IBDVs). The reverse transcriptase-polymerase chain reaction (RT-PCR) was used to amplify a 248-bp product, encompassing the hypervariable region of VP2 gene. The genotyping was conducted by restriction fragment length polymorphism (RFLP) analysis with six restriction endonucleases, DraI, SacI, TaqI, Sty, BstNI, and SspI. For the 150 samples received from the United States, 125 samples (83.3%) were RT-PCR positive for the presence of IBDV. One hundred positive samples (80%) had RFLP identical to the variant Delaware E strain, whereas 10 samples (8.0%) exhibited a RFLP pattern similar to this antigenic variant. Other IBDV strains such as Grayson Laboratory strain (GLS), Lukert, PBG-98, Delaware A, and the vaccine strains Sal-1 and D-78 were also detected. Two samples exhibited a pattern similar to the standard challenge (STC) strain, and seven strains (5.6%) were not classified by RFLP. Sixty-six bursal samples previously inactivated with phenol were received from Latin American countries. IBDV strains with analyzed genotypes similar to the Lukert strain were predominantly detected in Mexico. IBDV strains similar to variant E were detected in Colombia and Ecuador. Peru and Venezuela exhibited a higher heterogeneity of IBDV strains due to the detection of classic Delaware type as well as GLS variant strains. IBDV strains detected from Brazil and Dominican Republic exhibited RFLP patterns identical to very virulent IBDV strains prevalent in several countries in Europe, Asia, and Africa.