A hot saline antigen from Brucella ovis REO 198 was extracted to be us
ed in an indirect ELISA test (ELISA-I) for the diagnosis of sheep bruc
ellosis. This antigen was comparatively used in the ELISA-I and Gel Im
mune Diffusion test (IDG) in 1181 serum samples belonging to sheep of
different epidemiological statuses. The extracted antigen was highly h
ydrophilic performing the tests easily. The better relative sensitivit
y showed by the ELISA-I over IDG is discussed.