Avipoxviruses share several morphological, biochemical and physiochemical features with other poxviruses. Virus particles measure 270 × 350 nm and are composed of an electron dense, centrally located core and two lateral bodies that are visible in fixed and stained ultra-thin sections. In negative stained preparations, such as phosphotungstic acid (PTA) the membrane displays an outer-coat composed of a random arrangement of tubules [24] ; Figure 1 . APV particles have been shown to be resistant to ether, but sensitive to chloroform treatment [25] , although resistance to both chloroform and ether have been reported for pigeonpox virus and two pigeonpox virus mutants [26] .