In this study, the complete genome sequences of seven equine group A rotavirus (RVA) strains (RVA/Horse-tc/GBR/L338/1991/G13P [18] [12] from South Africa) were determined. Multiple novel genotypes were identified and genotype numbers were assigned by the Rotavirus Classification Working Group: R9 (VP1), C9 (VP2), N9 (NSP2), T12 (NSP3), E14 (NSP4), and H7 and H11 (NSP5). The genotype constellation of L338 was unique: G13-P[18]-I6-R9-C9-M6-A6-N9-T12-E14-H11. The six remaining equine RVA strains showed a largely conserved genotype constellation: G3/G14-P[12]-I2/I6-R2-C2-M3-A10-N2-T3-E2/E12-H7, which is highly divergent from other known non-equine RVA genotype constellations. Phylogenetic analyses revealed that the sequences of these equine RVA strains are related distantly to nonequine RVA strains, and that at least three lineages exist within equine RVA strains. A small number of reassortment events were observed. Interestingly, the three RVA strains from Argentina possessed the E12 genotype, whereas the three RVA strains from Ireland and South Africa possessed the E2 genotype. The unusual E12 genotype has until now only been described in Argentina among RVA strains collected from guanaco, cattle and horses, suggesting geographical isolation of this NSP4 genotype. This conserved genetic configuration of equine RVA strains could be useful for future vaccine development or improvement of currently used equine RVA vaccines.
INTRODUCTIONEquine group A rotavirus (RVA) strains were first detected in diarrhoeic foals in England in 1975(Flewett et al., 1975 and are a major cause of dehydrating diarrhoea in young 3Present address: Deltamune (Pty) Ltd, 248 Jean Avenue, Lyttelton, Centurion, 0140, South Africa.The GenBank/EMBL/DDBJ accession numbers for the equine rotavirus strains described in this study are JF712555-JF712565, JF712566-JF712576, JF712577-JF712587, JN872865-JN872875, JQ345489-JQ345499 and JN903507-JN903528. foals (Browning & Begg, 1996;Frederick et al., 2009; Imagawa et al., 1991;Saif et al., 1994). Serological data from Japan, the USA and France suggest that RVA is a ubiquitous pathogen in horse populations (Conner & Darlington, 1980;Imagawa et al., 1982;Pearson et al., 1982;Takahashi et al., 1979).RVA strains are icosahedral, non-enveloped viruses possessing a genome of 11 segments of dsRNA. The two outer capsid proteins, VP7 and VP4, elicit neutralizing antibodies independently and are used to differentiate RVA strains into G-types (glycoprotein) and P-types (proteasesensitive), respectively (Ciarlet & Estes, 2002 (Browning et al., 1991a). L338 was shown to possess the unique G13 and P[18] genotypes and a highly divergent NSP1 gene sequence, and to be distinct from other human and animal RVA strains by using RNA-RNA hybridization assays (Browning et al., 1991a; Iša & Snodgrass, 1994;Kojima et al., 1996;Taniguchi et al., 1994;Wu et al., 1993). In addition, a limited number of porcine-, bovineand feline-like RVA strains have been detected in horses. Examples include the G5P [7] RVA strain RVA/Horse-tc/ ...