An overview of calf diarrhea - infectious etiology, diagnosis, and intervention

Cho, Yong-il; Yoon, Kyoung-Jin

An antigen-capturing ELISA is performed for rapidly detecting a pathogen in a clinical specimen based on antibody (e.g., monoclonal antibody) recognition of the target antigen [74] . For this method, antibody is attached to a solid surface such as glass, plastic, or a membrane filter. The antibody captures target antigen present in the sample. A cascade of colorimetric reactions then verifies antigen capture and indicates an antigen-antibody reaction. Antigen concentration can be quantitatively estimated as optical density (OD) measured by spectrometry. The Ag-ELISA has been utilized in many fields. In particular, this method has been extensively performed in human diagnostic medicine. There are several platforms being used including the tube method, microtiter plate method, and membrane-bound method [38] . While the microtiter plate method has been commonly employed in diagnostic laboratory settings, the membrane-bound method using a lateral flow technique, such as a strip test, SNAP test, or rapid kits, is the most common platform for in-clinic or patient-side tests. Commercial Ag-ELISA kits for detecting BRV-A, BCoV, E. coli K99 + , and/or C. parvum in fecal samples are available. Ag-ELISAs are well known for rapid turnaround, high-throughput testing, plug-in-and-play capability, and portability [38] . Analytic sensitivity of this method tends to be lower than that of isolation/culture or nucleic-acid based assays [18] ; therefore, collection of samples from animals with acute diarrhea is important for reliable test results. For the best data, feces should be freshly collected from acutely affected calves. In some situations, the expense of a commercial kit may be cost-prohibitive.