703 blood samples from red foxes (Vulpes vulpes) were investigated to
determine the prevalence of antibody against an orthopox virus (vaccin
ia virus strain Elstree). A blocking-ELISA based on a neutralizing mon
oclonal antibody was used. In this assay 46 sera (6.5%) were positive
with titers of 1:2 to 1:16. ELISA-results were confirmed by the plaque
reduction test with 44 of the 46 sera reacting positively. The specif
icity of antibodies in 21 selected sera was also demonstrated by Weste
rn blot analysis.