63 (29) with default settings, except that we invoked the "scan for reassortment and recombination" setting to identify any reassortment between the gene segments of LAV strains of AHSV types 1, 3, and 4 and the 39 field isolate strains included in this study.
We used concatenated genome segments of 55 AHSV genomes to construct a maximum-likelihood phylogenetic tree incorporating best-fit substitution models (online Technical Appendix 2 Table 1, http://wwwnc.
Given that reassortment is a major feature of orbivirus evolution (30,31), we further explored the evolutionary relationships between the 55 AHSV sequences by constructing separate maximum-likelihood trees for each of the VP1, VP2, VP3, VP4, VP5, VP6, VP7, nonstructural (NS) protein 1 (NS1), NS2, and NS3 encoding genome segments (online Technical Appendix 2 Figures 1-10).
Similarly, changes in the AHS case definition that only came into effect in 2008 (after the 2004 Stellenbosch outbreak) probably resulted in an underestimation of subclinical AHSV infections during that outbreak.
Whole-genome sequences were compared from 55 field, LAV, and laboratory strains of AHSV.
24) hypothesized that changes in VP2 and VP5 can confer virulence or attenuation of individual AHSV strains, based upon comparisons of the consensus sequences of the genome of an attenuated AHSV-1 isolate (GenBank accession nos.
Given the genetic diversity of field strains of AHSV (14,24,35), our analyses overwhelmingly support the premise that the potential reversion-to-virulence mutants and reassortants that we detected arose from viruses within the polyvalent AHSV-LAV formulation, and predominantly from AHSV-1-LAV.
positive for antibody characteristic samples RVFV WNV
AHSV RVFV and WNV Origin Tata 2 0 0 0 0 Smara-Laayoune 58 13 20 0 11 Dakhla 40 2 9 0 1 Age group, y <1 18 1 1 0 1 1-2 25 0 1 0 0 3-5 7 1 3 0 1 6-10 27 6 12 0 10 >10 23 7 12 0 0 Sex M 71 10 15 0 7 F 29 5 14 0 5 Total 100 15 29 0 12 * RVFV, Rift Valley fever virus; WNV, West Nile virus;
AHSV, African horse sickness virus.