Evaluation of a new sandwich ELISA kit that uses serum for detection of cattle persistently infected with BVD virus

Cattle immunotolerant to and persistently infected (PI) with bovine viral diarrhea (BVD) virus (BVDV) constitute the mechanism by which BVDV persists in and spreads among cattle herds. Detection and elimination of PI cattle are necessary for control of BVD. Serum is an excellent specimen for BVD PI testing because of high survivability of BVDV in serum and ease of collection, storage, and handling. Currently, microtiter virus isolation (VI) employing serum and sandwich ELISAs (S-ELISA) on tissues or leukocytes are used for BVDV PI screening. This paper evaluates a new S-ELISA kit that uses serum as the diagnostic sample. Cattle sera (n = 408) were tested using VI and the S-ELISA. The VI detected 172 BVDV-positive sera. Of these, 18 were confirmed PI cattle. The S-ELISA was positive on all PI samples. Considering only the PI animals, and using VI as the gold standard, the relative sensitivity of S-ELISA was 100%. The overall relative sensitivity was 93.6% and the agreement quotient (kappa) was 0.94. The relative specificity of the kit, based on 236 VI-negative sera, was 100%. These data indicate that the new kit is very adequate for detection of BVDV PI cattle.