Diversity and selection in Babesia bovis and their impact on vaccine use.

In the past few years the prospect of a recombinant vaccine effective against the cattle hoemoparosite Babesia bovis has almost become a reality. However, in Australia, vaccination with live parasites has been practised since before the turn of the century and it has recently been proposed that selection of parasites resistant to immunity induced by the B. bovis line Ka (since 1979 the only component of the live attenuated vaccine) may have occurred. Brian Dalrymple examines the evidence for and against this proposal and discusses examples of strain diversity and variation and their effect on the long-term viability of defined attenuated and recombinant vaccines.