If you own a horse, you are likely familiar with Coggins testing. Numerous horses come by our clinic each year for this annual ritual. I find that while many owners know that the test is required and have had it performed on their horses numerous times, they still have questions about what the test is really for and why it is necessary.
‘Coggins’ is actually the name of the test that is most commonly used to identify a horse’s immune response to the disease ‘Equine Infectious Anemia’ or EIA. The test got its name from its developer, Leroy Coggins, in 1970. EIA is caused by a retrovirus. Similar to HIV in humans, this virus incorporates its DNA into the infected animal’s own cells. There is no vaccine and no treatment and the disease is potentially fatal. For these reasons significant measures are in place to control the spread and prevalence of the disease.
The EIA virus can cause one of three clinical forms of disease once a horse, donkey or mule is infected. The first potential form is called the acute form in which the animal becomes very ill and spikes a significant fever. The disease may progress rapidly ending in death in two to three weeks. If the animal survives the acute stage it may become a chronically infected horse, the second clinical form or can become an inapparent carrier, the third clinical form. Chronically infected horses have recurring bouts of illness characterized by fever (105-108° F), weight loss, small hemorrhages and swelling of the legs and underline.
Its the inapparent carriers, however, that are the most dangerous as they parade around as apparently healthy animals all the while serving as sources of exposure to all other horses they may come in contact with. The majority of infected horses actually fall into this ‘inapparent carrier’ category. Given that EIA is a blood-borne disease transmitted primarily by blood-feeding flies, these horses can serve as a significant source of exposure, primarily in situations in which horses are congregated in large groups. Such events as trail rides, shows, rodeos and sales provide opportunity for spread of EIA if infected horses are present. For this reason all managed or sponsored events in the state of Missouri require that a current negative coggins test be presented before participation. Additionally, a negative test is required for horses changing ownership, crossing state lines, going to an auction market, horses maintained at breeding/boarding/training facilities or being used on public lands. It is advisable to have all horses on your premises tested on an annual basis. All horses that test positive must be reported to the appropriate authorities and euthanasia or quarantine measures are then instituted.
While this disease has the potential to be devastating to the equine industry, the current testing and control measures in place are relatively effective in controlling the disease. An unofficial report from the state vet’s office reports no positive cases in the state this year.
Darren Loula, DVM, is a large animal veterinarian at Fair Grove Vet Service in Fair Grove, Mo.
