Assessment of an indirect ELISA in milk for the diagnosis of ovine brucellosis

Abstract

The possibility of using an ELISA for the diagnosis of ovine brucellosis in milk (M-ELISA) was investigated. The aim of the study was to establish whether the specificity and sensitivity of the M-ELISA would be high enough to detect low levels of Brucella antibodies in ewe milk. The diagnostic performances of the test under study were established by means of reference standards and compared with conventional screening and confirmatory tests under field conditions. The diagnostic specificity of the M-ELISA established on a number of samples from Brucella-free flocks was 100% while relative to RBT and CFT positive reactors the M-ELISA demonstrated sensitivity of 65 and 83% respectively. Its sensitivity relative to culture positive animals was of 92%. The course of Brucella antibodies in milk of positive sheep was evaluated in colostrum and in mature milk for a period of 30 days after delivery and it appeared that concentrations of immunoglobulins in milk tend to sharply decrease soon after parturition while in blood serum these remained constantly high. It was concluded that the M-ELISA for Brucella antibodies in ewe milk can be regarded as a complementary diagnostic tool for individual testing but it would be poorly viable if used as a screening test applied to pooled flock milks.