Two Missouri horses have been diagnosed with equine infectious anemia (EIA), a serious reportable disease for which control measures are equally serious and aggressive.
The two horses from northeastern Missouri were diagnosed with the infection in January. The first horse, a Belgian, was diagnosed on January 5 and was promptly euthanized – because of the seriousness of EIA and the potential for transmission to other horses, prompt euthanasia or transportation of any positive horse to an approved quarantine facility is required. Two days later, another horse on the farm was diagnosed and was also euthanized.
The disease, caused by equine infectious anemia virus, is spread by certain biting insects or cross-contamination of blood (e.g. reusing needles), so finding more than one infected horse on a property isn’t too surprising. While the response to an infected horse may seem draconian, EIA can cause widespread and severe illness, and elimination of carriers (i.e. positive horses, which are all infected for life) is a critical component of keeping it under control.
Six-hundred and ninety-six (696) other horses, including horses from nearby farms and horses in contact with the infected horse, have been tested in response to these two positive animals, which is another indicator of how seriously control of this disease is taken. All the other horses tested were negative, and there is currently no evidence that any other horses are infected.
The fact that no other infected horses were identified is good, as it’s unlikely the virus has spread widely in the area. However, it doesn’t explain where these horses got infected. EIA virus doesn’t occur spontaneously – it had to come from somewhere. The origin of the infection is presumably being investigated, but it can be tough to find. Some infected horses have chronic infections with few or no (or intermittent) clinical signs. Therefore, an infected horse can be a source of infection for some time before it is identified, particularly if it is not required to be tested for transportation or competition (using a Coggin’s test). There was another horse in Missouri that tested positive for EIA in August 2010 as well. Hopefully, this isn’t a “tip of the iceberg” situation, and Missouri officials hopefully have a good idea of the true number of infected horses. Only time will tell, unfortunately.