Virus Isolation from Semen of Bulls Serologically Positive for Bluetongue Virus

Isolation of bluetongue virus was attempted from 85 semen samples taken from 3 long-term seropositive bulls and 9 short-term seropositive bulls in an artificial breeding service unit. Two types of cell cultures susceptible to bluetongue virus were used for virus isolation. Extended sonication, centrifugation of specimens, and treatment of cell cultures with dimethyl sulfoxide and diethylaminoethyl-dextran were used to enhance virus attachment and infection of cell cultures. Virus isolation results were negative on all specimens. These results indicate that at the limits of the methods used, bluetongue virus-seropositive bulls do not have long-term latent bluetongue virus in their semen.