Clinical and serological outcome following the simultaneous inoculation of three bluetongue virus types into sheep.

The simultaneous inoculation of sheep with three different bluetongue virus types resulted in the replication of only two of the virus types and the formation of neutralising antibodies to only those two types and a failure in the production of heterotypic antibodies. This suggests that the present system of control, using multivalent vaccines in areas in which a number of bluetongue serotypes exist, should be reappraised.