The invention relates to an isolated African horse sickness virus (AHSV) ssRNA comprising a plurality of mutations; a complementary cell for replication of a vaccinal viral strain from said ssRNA; a vaccinal viral strain derived from said ssRNA; use of said vaccinal viral strain and/or isolated ssRNA in the vaccination of an animal against an infection by AHSV; a method of vaccination comprising same; and a pharmaceutical composition comprising said vaccinal viral strain and/or said isolated ssRNA.

The invention relates to methods for producing a propagation-competent strain of a mutant Reoviridae virus, and to a propagation-competent strain of a mutant Reoviridae virus that is obtainable by a method of the invention. The invention further relates to a propagation-competent strain of a mutant Reoviridae virus, comprising a deletion of a genetic region that is relevant for propagation of the virus, and to a vaccine, comprising a propagation-competent strain of a mutant Reoviridae virus.