Recovery of bluetongue virus serogroup from sera collected for a serological survey from apparently healthy cattle, from the Sudan

Virus of the bluetongue (BT) serogroup was recovered from 11% of cattle sera collected from apparently healthy animals in Khartoum Province for the sole purpose of screening for BT antibodies. Since these sera did not contain BT antibodies, the donor cattle could have been scored as BT free in the serological survey. Virus was initially isolated in chicken embryos inoculated intravascularly, and was further adapted to Vero cell cultures. Isolates were identified as belonging to the BT serogroup using the agar gel immunodiffusion (AGID) and complement fixation (CF) tests. The results indicated that cattle in the Sudan could harbour BT virus without showing symptoms of the disease. Such an observation necessitates further work to clarify the role of cattle in the epidemiology of BT in the Sudan.