COMPARISON OF IMMUNOHISTOCHEMISTRY, ELECTRON-MICROSCOPY, AND DIRECT FLUORESCENT-ANTIBODY TEST FOR THE DETECTION OF BOVINE CORONAVIRUS

Bovine coronavirus (BCV) is 1 of the major causes of calf diarrhea and has also been implicated in respiratory infections of young calves an d winter dysentery of adult cable. Currently, transmission electron mi croscopy (TEM), direct fluorescent antibody (DFA), and enzyme-linked i mmunosorbent assay (ELISA) techniques are considered standard methods for the diagnosis of BCV infection. However, these techniques are not useful if fresh tissues and intestinal contents are not available for examination. The detection of viral antigens in formalin-fixed, paraff in-embedded tissues using immunohistochemistry (IHC) is a suitable alt ernative. In the present study, 166 tissue specimens were tested by IH C for the presence of BCV. These tissues were from animals whose feces were positive for rotavirus and/or coronavirus by TEM. Some of these samples were also tested by DFA. Thus, TEM, DFA, and IHC were compared for the detection of BCV. There was 56% agreement among the 3 methods (overall kappa = 0.368). When MC was compared with TEM, 78% agreement was observed (kappa = 0.475). Similarly, IHC and DFA had 64% agreemen t (kappa = 0.277). These kappa values indicate a moderate degree of ag reement between IHC and TEM; agreement between IHC and DFA was fair. T he results of this study indicate that IHC may be a suitable adjunct f or the detection of BCV because of its simplicity, ease of use, and re latively close correlation with TEM results.