Diversity of infectious pancreatic necrosis virus strains isolated from fish, shellfish, and other reservoirs in northwestern Spain

A comparison was done of 231 strains of birnavirus isolated from fish, shel lfish, and other reservoirs in a survey study that began in 1986 in Galicia (northwestern Spain). Reference strains from all of the infectious pancrea tic necrosis virus serotypes were included in the comparison, which was don e by neutralization tests and agarose and polyacrylamide gel electrophoresi s of the viral genome. The neutralization tests with antisera against the W est Burton, Spajarup (Sp), and Abild (Ab) strains showed that most of the G alician isolates were European types Sp and Ab; however, many isolates (30% ) could not be typed. Results from agarose gels did not provided informatio n for grouping of the strains, since all were found to have genomic segment s of similar sizes. Analysis of polyacrylamide gels, however, allowed six e lectropherogroups (EGs) to be differentiated on the basis of genome mobilit y and separation among segments, and a certain relationship between EGs and serotypes was observed. A wide diversity of electropherotypes was observed among the Galician isolates, and as neutralization tests showed, most of t he isolates were included in EGs corresponding to European types Ab and Sp. Only 6.5% of the isolates had the electropherotype characteristic of Ameri can strains.