The occurrence of antibody to Babesia and to the virus of louping-ill in deer in Scotland.

Sera of wild red deer from 16 localities in Scotland were tested by the indirect fluorescent antibody technique for antibody to Babesia and by the haemagglutination inhibition test for antibody to the virus of louping-ill. Babesial antibody was detected in sera from all localities in proportions ranging from 22 to 100 per cent. Antibody to louping-ill virus could not be demonstrated in sera from five of the localities and in the other 11 was found less frequently than was antibody to Babesia. Sera from male and female deer were positive for louping-ill in almost equal proportions whereas the incidence of babesial antibody was significantly lower in females than in mature males. This difference could be explained by the habits of the deer. The variable occurrence of louping-ill antibody suggested that red deer are tangential hosts for the virus.