“…With EAV, variation has been detected within an outbreak, between virus isolates from the same carrier stallion over an extended period and also among isolates worldwide (Murphy et al, 1992). The genomic variability of LDV has also been described in reviews by Rowson & Mahy (1985), and Plagemann & Moennig (1992). High mutation rates are a feature of RNA viruses (Holland et al, 1982), and can lead to the establishment of heterologous populations, described as quasispecies (Domingo et al, 1985).…”