Despite the worldwide prevalence of APV infections, experimental infection studies in birds using APVs have centred on relatively few viral isolates. Analyses of variation have essentially focused on a FWPV strain termed the prototype, while a minority of experimental studies have been reported on CNPV, quailpox, juncopox, and pigeonpox virus isolates [4, 48, 49] . In fact, in the last twenty years, approximately 50% of published studies on APVs have been on the FWPV isolate directly (based on a PubMed search on APVs). The important nature of APVs which has been used successfully for vaccine development mandates that a larger pool of viral strains should be analyzed both for consideration of pathogenesis and determination of immune correlates of protection.