Development of a mouse model system, coding assignments and identification of the genome segments controlling virulence of African horse sickness virus serotypes 3 and 8

Attenuated (att) and wild type (wt) strains of the nine AHSV serotypes were evaluated for virulence in adult Balb C mice. Although most were avirulent in this system, isolates of AHSV latt, 3wt, 3att, 4wt, 4att, 5att, 7att and 8att caused some mortality when administered via an intranasal route. After plaque cloning, only the attenuated vaccine strain of AHSV 7att caused any mortality via an intravenous route. AHSV 3att and AHSV 8wt were virulent (V) and avirulent (AV) (respectively) in the mouse model and were selected as parental strains for production of genome segment reassortants. These progeny virus strains were plaque cloned, then characterised to identify the genome segments that influence virulence of AHSV in the mouse model.