Rapid immunofiltration assay as a field diagnostic tool for ovine brucellosis

This work describes the development of two rapid immunofiltration assays, enzymatic (ERIFA) and non-enzymatic (NERIFA), for the rapid detection of ovine anti-Brucella antibodies. Brucella abortus lipopolysaccharide and total bacterial extract were dotted separately as diagnostic antigens on a nitrocellulose filter-membrane of the individual assay unit along with a third dot of purified sheep IgG as an internal control. The assay's diagnostic performance was evaluated in comparison with a modified rose bengal test (mRBT) and an indirect enzyme-linked immunosorbent assay (ELISA) through usage of 590 serum samples from healthy, vaccinated, or infected sheep. The ERIFA and indirect ELISA were found to be significantly more sensitive than NERIFA, while mRBT was determined to be statistically equivalent to NERIFA. A perfect agreement (κ = 0.984) and a statistical equivalence to indirect ELISA suggest that the bi-antigenic ERIFA can be used as an "individual rapid ELISA" for screening ovine anti-Brucella antibody both in the field and in limited laboratory conditions.