For the horse owner, the main differences between the Coggins or AGID test and the ELISA test will be the speed in which you can get the final report and the cost. ELISA tests are also not as accurate as a Coggins, so in the case of a positive result a Coggins test may be done to verify the results. There may be some states or countries that do not accept the ELISA tests. Talk to your vet about which one will be the best choice in your situation.
What If I Get a Positive Coggins Test Result?Unfortunately, a positive Coggins test is very bad news. Most authorities recommended humane euthanasia. The alternative is complete life long quarantine and restricted transport. EIA is carried by mosquitoes so the horse must be kept in a way that keeps mosquitoes from biting it, and then carrying it to another horse. In many states this means keeping a horse further than three miles from another equine. In some states, a horse that has tested positive for EIA must be identified in some way, usually with some type of brand. If other hoses are exposed to the horse at any time, they too must be tested, and retested to be sure there are no new infections.
With the dire outlook that comes with a positive result, it's tempting to avoid having horses tested for EIA. But, my vet assured me, EIA is less prevalent in areas where Coggins tests are most often done. The more horses tested, the quicker outbreaks are found, and the fewer horses will be infected.
Links to specific requirements and regulations regarding EIA for each state can be found on the University of Vermont: Equine Infectious Anemia page.