Genotyping of Canadian field strains of infectious bursal disease virus.

For this retrospective study, infectious bursal disease virus (IBDV) was detected in 134 bursal samples that originated from flocks with conditions such as airsacculitis, tracheitis, pneumonia, septicaemia, inclusion body hepatitis, coccidiosis, and/or a history of production problems without overt clinical symptoms. Samples were from seven Canadian provinces: Ontario, Quebec, Manitoba, British Columbia, Nova Scotia, Alberta, and Newfoundland and Labrador. Viral RNA was identified in bursae with moderate to severe and acute to chronic bursal damage. The ages of the flocks from which samples were collected ranged from 3 to 63 days. Following reverse transcriptase-polymerase chain reaction the nucleotide sequence of the VP2 hypervariable region was determined and compared with sequences available in GenBank. The most common Canadian IBDV field strains were North-American variant viruses. Forty-four viruses were highly related (97.5% to 100.0%) to the US IBDV strain NC171. Moreover, 16 field viruses whose VP2 sequences were 99.2% to 100% identical to the South African 05SA8 IBDV strain appeared closely related to the NC171 group. Delaware E-related field viruses, 98.3% to 100.0% identical to the prototype virus, were identified in 33 samples. Thirty-four Canadian IBDVs showed the highest identity, 94.2% to 98.3%, to US IBDV strain 586. Five samples contained vaccine-related viruses, while two field strains showed the best match to Del A (United States) and IBDV strains SP_04_02 (Spain). Very virulent IBDVs were not detected in Canada.