Serology has been widely used for diagnosis, but has
complicated the understanding of V. anguillarum extent
traversed species boundaries. With V. anguillarum, serogroup
02 and 05, there are common antigens with V.
ordaliiand V. harveyi , respectively. Initially,
three serotypes were recognised for isolates from salmonids
from the northwest USA, Europe, and the Pacificnorthwest
(USA). This number increased to
6 , and then 10and upwards. Serogroup
O1 dominates the number of isolates available
for study and the relative importance to fish pathology
. Serogroup O2 has been further subdivided
into serogroup O2a and O2b