Counterimmunoelectroosmophoresis for detection of neonatal calf diarrhea coronavirus: methodology and comparison with electron microscopy.

A counterimmunoelectroosmophoresis (CIE) technique is described for the detection of calf diarrhea coronavirus antigens in intestinal contents. The antibody reagent was prepared in rabbits against the Nebraska calf diarrhea coronavirus adapted to Vero cells and purified by density gradient centrifugation. The method was applied to intestinal contents of diarrheic and normal calves and compared with electron microscopy (EM). Calf coronavirus antigens were detected in intestinal contents of 44% (21/48) of the diarrheic calves and 24% (4/17) of the normal calves. Two precipitin lines could be observed in the majority of the positive samples. When compared with EM, CIE detected more positive animals. In only two cases (2/20) CIE was negative despite the visualization of coronavirus particles by EM.