Grey squirrels have high seroprevalence to a parapoxvirus associated with deaths in red squirrels

The population of red squirrels (Sciurus vulgar-is) in the British Isles is in decline and is being supplanted by the grey squirrel (Sciurus carolinen sis). It has been suggested that parapoxvirus-associated disease has caused significant mortality in red squirrels and that grey squirrels are the sou rce of the virus. A direct enzyme-linked immunosorbent assay (ELISA) was de veloped for the measurement of antibody to squirrel parapoxvirus. We tested 140 sera from red squirrels and 223 from grey squirrels from different pop ulations in the UK. A high percentage (61%) of apparently healthy grey squi rrels, were found to have been exposed to the parapoxvirus. Only 2.86% (4/1 40) of red squirrels had antibody and three of these animals had parapoxvir us-associated disease. We postulate that the grey squirrel may act as a res ervoir host for the virus.