Avipoxviruses are large, oval-shaped enveloped viruses whose genome consists of double stranded DNA ranging in size from 260 to 365 kb [8] . Unlike most other DNA viruses, APVs replicate easily in the cytoplasm of infected avian cells which results in a characteristic cytopathic effect (CPE) 4 to 6 days post infection depending on the virus isolate [4] . APVs also multiply on the chorioallantoic membrane (CAM) of embryonated eggs, resulting in the formation of compact, proliferative pock lesions that are sometimes focal or diffuse [15] . However, some isolates, especially from the host species great tit (Parus major), have failed to multiply on CAM of chicken embryos [16] . APVs are the etiologic agent of disease characterized by skin lesions in both wild and domestic birds [4, 5] . Histologically and ultrastructurally, APVs undergo morphologic stages that are similar to other chordopoxviruses, including the formation of intracytoplasmic inclusions bodies, a characteristic which has been observed in some epithelial and mononuclear cells of permissive hosts. APV particles can be detected and further characterized by use of transmission electron microscopy (TEM) [17, 18] .