Pen-side testing

Pen-side diagnostic testing is often required to provide real time information about the health status of an animal or herd. The rapid results are generally needed in the face of a disease outbreak where the diagnostician/clinician is presented with dead or dying animals. Another use of pen-side tests is as part of a preventive medicine/herd health programme, where the information can be used for determining pathogen incidence and prevalence in the herd, identifying potential carrier animals or evaluating subtle changes in overall herd health as a result of management changes. Still another area is as a part of health certification before sale or stocking, or during processing following slaughter. Advanced testing methods, which in the past were only appropriate for use in a laboratory setting, have now been formatted for use in the field. Enzyme immunoassays (EIAs) and immunochromatorgraphy have greatly enhanced diagnostic pen-side capabilities. These test systems allow for the rapid, sensitive and specific detection of target antigen or antibody and require little or no scientific equipment. Because of the wide format flexibility these immunochemical technologies allow, they have come to dominate the diagnostic industry, both in the laboratory and in the field. Using liquid phase or precipitating chromogens, the tests can be visually interpreted and do not need instrumentation. Immunochromatography, a simplified assay system, has found widespread application as a field or pen-side test. The entire assay takes only one or two steps, and the results appear within 5-10 minutes. In the future, DNA based diagnostics will become more adaptable for use in the field. The DNA hybridization systems are at present cumbersome and require elevated temperatures. Companies are currently working to develop fast formulas that provide results in less than an hour, have a limited number of steps and can be performed at lower temperatures. (author)