DETECTION OF BLUETONGUE VIRUS AND AFRICAN HORSESICKNESS VIRUS IN CO-INFECTED CELL-CULTURES WITH NS1 GENE PROBES

The serogroup specificity of the bluetongue virus (BTV) NS1 and VP3 ge ne probes was confirmed by means of northern blot hybridization. Under high-stringency conditions both probes hybridized to 22 BTV serotypes (18 South African serotypes, BTV3 from Cyprus and BTV16 from Pakistan ) but not to serotypes that originate from Australia and India. Furthe rmore, NS1 gene probes of BTV and African horsesickness virus (AHSV) w ere used in a dot-spot in site hybridization procedure to differentiat e between BTV and AHSV in co-infected cell cultures. The method detect s viral RNA directly in glutaraldehyde-fixed infected cell cultures wi thout prior nucleic-acid extraction or purification. AHSV could be det ected in cells infected with AHSV at a multiplicity of infection of 10 (-4) PFU/cell in the presence of a hundredfold excess of co-infecting BTV. The method may have an application in epidemiological surveys to detect different orbiviruses in the same Culicoides population.